Author Topic: Required lift for 42" tires  (Read 1146 times)

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Offline Signguy97

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Required lift for 42" tires
« on: November 11, 2020, 02:07:18 pm »
Hey guys , I had a couple of posts about a drivetrain swap I am starting on my 75 ramcharger, the project has taken a different turn, I was planning to swap the 360 for a 440, that fell through but I just purchased a 92 diesel 4x4 that has everything I need to swap in the 5.9 and the Dana 70/60 axles. I'll have lots of questions as I go along but I am still going with the 42" tires and I'm wondering how much lift I will need to clear the stock fenders, this truck is in beautiful shape for a 75 and has the SE trim so I don't want to cut the fenders out. I can radius the bottom edges a bit but that's about all. I currently have a skyjacker 8" suspension lift, I was planning on installing a three inch body lift and just wondered if that will be enough or will I need a bit more suspension as well. I have measured up the new axels and I think they will give me about an 1-1/2" of lift on there own.
Also if I do lift it more with a shackle flip etc. How do you get the driveline angles to work, I already had to drop the transfer case and hog out the joints as it is?

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    Offline u2slow

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    Re: Required lift for 42" tires
    « Reply #1 on: November 11, 2020, 02:17:51 pm »
    Darn small fender openings to fit 42's without some mega lift.  :-\  I would find a 2nd set of fenders to modify. https://www.dieseltruckresource.com/forums/1st-gen-ram-all-topics-93/interesting-caravan-pics-248172/#post2534322

    These are 37's rolled under a '77 sitting on blocks.


    DD: 90 D250 6BT|5spd|D60/3.54/Lockright
    Tow/haul: 93 W250 Club 6BTA|5spd|D60/80/3.54/Lockright|4" lift|35's|HX35|5x.012s|4" pipe
    Projects: '84 D250 Ramcharger (cummins); '90 W250 Ramcharger (360TBI)
    Hers: 2005 Jeep Liberty V6|6spd|3.73/Trac-lok |3" lift, 245/75R16E Nokians

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    Re: Required lift for 42" tires
    « Reply #2 on: November 11, 2020, 03:39:33 pm »
    Here's an 87 RC I built for a friend - it's got 40s, 4" lift springs (48" Dodge fronts, 56" Chevy rears), and a 3" body lift.  Had to trim the front fenders to allow for turning and articulation (this truck is built for on and off-road), but the rear quarters are untouched.







    I highly recommend either 56 or 63" rear leafs, and 52" front leafs - doing so will give you a better ride, with the same weight-carrying capacity.  Naturally you'll relocate the leaf spring mounts.  If you are looking for the best aftermarket spring mounts look at Jungle Jim's hardware in the vendors section - if you get his mounts you likely won't need the body lift, or at least not as tall of a body lift.

    On the rear axle rotation, you will need to cut/separate the leaf spring perches on rear axle, rotate the axle to aim straight at the t-case, and have a custom double cardan driveshaft made - dc joint at the t-case.

    42's are a big tire without trimming fenders, but if you do it nicely you can make it look like it came that way.

    - Sam
    « Last Edit: November 11, 2020, 03:50:50 pm by Mad Max »
    2002 Dakota Quad Cab 4x4 - 440/46rh/Atlas4/D60/14b/40s
    2007 Cummins Ram 3500 Megadually 4x4 "Big Mack" - 5.9/G56 6-speed
    2016 Durango Citadel AWD - 5.7 Hemi/8-spd auto
    1952 Willys M-38 "Poncho"

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    Offline u2slow

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    Re: Required lift for 42" tires
    « Reply #3 on: November 11, 2020, 04:31:35 pm »
    I'm quite sure the older fenders have smaller wheel-well openings...
    DD: 90 D250 6BT|5spd|D60/3.54/Lockright
    Tow/haul: 93 W250 Club 6BTA|5spd|D60/80/3.54/Lockright|4" lift|35's|HX35|5x.012s|4" pipe
    Projects: '84 D250 Ramcharger (cummins); '90 W250 Ramcharger (360TBI)
    Hers: 2005 Jeep Liberty V6|6spd|3.73/Trac-lok |3" lift, 245/75R16E Nokians

    Offline Signguy97

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    Re: Required lift for 42" tires
    « Reply #4 on: November 12, 2020, 10:37:46 am »
    Here's an 87 RC I built for a friend - it's got 40s, 4" lift springs (48" Dodge fronts, 56" Chevy rears), and a 3" body lift.  Had to trim the front fenders to allow for turning and articulation (this truck is built for on and off-road), but the rear quarters are untouched.







    I highly recommend either 56 or 63" rear leafs, and 52" front leafs - doing so will give you a better ride, with the same weight-carrying capacity.  Naturally you'll relocate the leaf spring mounts.  If you are looking for the best aftermarket spring mounts look at Jungle Jim's hardware in the vendors section - if you get his mounts you likely won't need the body lift, or at least not as tall of a body lift.

    On the rear axle rotation, you will need to cut/separate the leaf spring perches on rear axle, rotate the axle to aim straight at the t-case, and have a custom double cardan driveshaft made - dc joint at the t-case.

    42's are a big tire without trimming fenders, but if you do it nicely you can make it look like it came that way.

    - Sam

    Thanks Sam, a fellow below commented on the wheel openings being bigger on the later trucks like yours, and I don't think that is the case, I measured the ones on this 92 truck that I bought and they are the same as my 75. You didn't mention the front driveshaft, and that is the one I had real problems with already , hopefully I won't have to go any higher with the suspension

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    Re: Required lift for 42" tires
    « Reply #5 on: November 12, 2020, 11:43:40 am »
    "clocking the C's" (rotating the front pinion up) on a front axle is a lot lot lot more complicated (and difficult) than a rear, especially when using leaf springs, but it certainly can be done, and depending on your situation it may be 100% necessary, and then there's potential input bearing oiling problems but one problem at a time.

    What are you intended plans for the truck - presumably serious off-roading, but mud wheeling? rock crawling...?
    2002 Dakota Quad Cab 4x4 - 440/46rh/Atlas4/D60/14b/40s
    2007 Cummins Ram 3500 Megadually 4x4 "Big Mack" - 5.9/G56 6-speed
    2016 Durango Citadel AWD - 5.7 Hemi/8-spd auto
    1952 Willys M-38 "Poncho"

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    Offline Mopar572

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    Re: Required lift for 42" tires
    « Reply #6 on: November 12, 2020, 01:32:32 pm »
    "clocking the C's" (rotating the front pinion up) on a front axle is a lot lot lot more complicated (and difficult) than a rear, especially when using leaf springs, but it certainly can be done, and depending on your situation it may be 100% necessary, and then there's potential input bearing oiling problems but one problem at a time.

    What are you intended plans for the truck - presumably serious off-roading, but mud wheeling? rock crawling...?

    I agree...what are your plans.  42s are one thing on a buggy or a purpose built off roader but what are your plans for a fullsize truck with 42" tires and purty sheetmetal.  Trails that require 42s generally require far less sheetmetal.
    1985 W250, 318, 435, 208, 44/60
    1991 W350, 360, 435, 205, 60/70
    1991 D250, 360, 518, 60

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    Re: Required lift for 42" tires
    « Reply #7 on: November 12, 2020, 03:17:47 pm »
    not to mention you'll need really deep gears too - the RC I posted runs 5.86's.  Also, tires that big and diesel torque can easily snap stock axle shafts... :-\
    2002 Dakota Quad Cab 4x4 - 440/46rh/Atlas4/D60/14b/40s
    2007 Cummins Ram 3500 Megadually 4x4 "Big Mack" - 5.9/G56 6-speed
    2016 Durango Citadel AWD - 5.7 Hemi/8-spd auto
    1952 Willys M-38 "Poncho"

                    .there's always a way...

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    Offline 712edf

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    Re: Required lift for 42" tires
    « Reply #8 on: November 12, 2020, 04:45:36 pm »
    A W600 will fit 42" with room to spare.  ;D ;D

    Bucky
    1975 W600   318  NP540  T223Rockwell tcase, Rockwell front & rear axles, 6.8 ratio

    Offline Signguy97

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    Re: Required lift for 42" tires
    « Reply #9 on: November 13, 2020, 03:53:35 pm »
    "clocking the C's" (rotating the front pinion up) on a front axle is a lot lot lot more complicated (and difficult) than a rear, especially when using leaf springs, but it certainly can be done, and depending on your situation it may be 100% necessary, and then there's potential input bearing oiling problems but one problem at a time.

    What are you intended plans for the truck - presumably serious off-roading, but mud wheeling? rock crawling...?


    I do plan to off-road the truck but nothing too crazy, the body is too nice to get wrecked

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    Re: Required lift for 42" tires
    « Reply #10 on: November 14, 2020, 09:53:13 am »
    well what I was getting at is if you're not doing serious rock crawling - which places the belly and hardware in mortal danger - then you could consider clocking your t-case down to reduce the front driveshaft angle.  Some OE t-cases all for this and some don't - just depends on your transmission rear mating flange, etc.

    Also, while this probably won't sound like too good of advice, try not to worry too much about wrecking the body and instead just go enjoy the truck.  If you go off road even once then you sign up for body damage, but unless you're going where there's BIG rocks and/or lots of trees then you likely won't have much to worry about. 

    Plus, the old adage still applies regarding off-roading and body damage:  "There are those that have...and those that will".  Once you accept it, the whole thing gets a lot more fun ;) ;D

    - Sam
    2002 Dakota Quad Cab 4x4 - 440/46rh/Atlas4/D60/14b/40s
    2007 Cummins Ram 3500 Megadually 4x4 "Big Mack" - 5.9/G56 6-speed
    2016 Durango Citadel AWD - 5.7 Hemi/8-spd auto
    1952 Willys M-38 "Poncho"

                    .there's always a way...

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    Offline RedneckInTraining

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    Re: Required lift for 42" tires
    « Reply #11 on: November 14, 2020, 11:03:36 pm »
    I agree, offroad body damage up to and including a complete write off is possible. If your not mentally prepared to write off your vehicle every time you hit the trails you have no business offroad. My rule for body damage is as long as it doesn't take out the glass,lights, or prevent the doors from opening I don't care. I've had one vehicle where I tried to preserve the body because it was "pristine", which was a 1990 Geo tracker 2 door. I wheeled everywhere with that little creature with 235/75/15 tires at stock height with a spool, with no real body damage to speak of. Then I installed a 2" lift and some 31x10.5x15 tires. The very next weekend while playing in a rocky creek bed I smashed both rocker panels to where I needed to kick the doors open and hammer the door sills back down. That same day, I removed both mirrors and the passenger taillight trying to squeeze through two trees that just happened to be tracker width apart. The next day a buddy was riding shotgun for some night wheeling and he didnt say anything about the 4ft boulder I was about to come down on until I caved in the passenger door and pivoted around the rock. On that trip I stopped caring about body damage 30 minutes in on day one after I realized how much better it wheeled after the rockers self clearanced. I would also like to point out that on day 2 there was a rocky obstacle that the bigger vehicles were having trouble with. I posted the "high water mark" and lost my driver side tail light in the process. My record stood until a tube buggy on 40's got through it with some difficulty. Now I'm not saying a wheeling rig has to look like a crumpled up beer can, its just that body damage is kinda to be expected...
    « Last Edit: November 14, 2020, 11:07:14 pm by RedneckInTraining »
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    Offline RXT

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    Re: Required lift for 42" tires
    « Reply #12 on: November 14, 2020, 11:50:47 pm »
    Anything is possible, but you're gonna have to make some serious compromises. The combination of big lift, and short wheelbase is going to be hard to reconcile. The one good thing is you won't need really low gears with a Cummins. If built right, they can produce more than enough torque to turn big tires with taller gears. I'm personally running 4:56 and 42s and my Cummins pulls it just fine.

    The issue is drivetrain and lots of lift. You need lots of lift to avoid cutting fenders, but that means your driveshafts will have to run at steeper angles. The problem is the greater the angle, the more the u-joints will have to take. At higher angles, they will not last very long. There are several options to reduce driveshaft angles and you'll probably have to combine them and it still might not fully resolve the issues.

    So your compromises will be as follows;

    Live with the short u-joint life, no or little daily driving
    Reduced ground clearance for the tire size chosen (thru lowered t-case, clocked t-case)
    Choose a smaller tire and a smaller lift
    or cut the fenders

    Ed
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    Offline RedneckInTraining

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    Re: Required lift for 42" tires
    « Reply #13 on: November 15, 2020, 06:04:13 am »
    They make industrial CV joints, If you insist on a silly lift with a short wheelbase you could use some of those for driveshafts. If you have a slip yoke in the driveshaft you can use CV joints with a 45* max operating angle which blows a U joint's max operating angle of 3* out of the water.
    « Last Edit: November 15, 2020, 06:08:03 am by RedneckInTraining »
    1994 Dodge Ram 2500 CTD
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    Offline Chilly

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    Re: Required lift for 42" tires
    « Reply #14 on: November 15, 2020, 07:40:59 am »
    Seems likely you'll ruin a nice body.  Might as well thoughtfully and tastefully ruin it in advance by massively trimming the fenders, go with minimal lift for belly clearance, keep low center of gravity.  Might even consider some M715 style fenderwell inserts from a 55 gal drum.
    92 Ramcharger
    360 TBI, auto, 241 t-case
    44F, 9.25R posi, 3.54 gears (yeah, I know)
    Skyjacker 4", 33x12.5

    Offline RXT

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    Re: Required lift for 42" tires
    « Reply #15 on: November 15, 2020, 09:57:24 am »
    They make industrial CV joints........... If you have a slip yoke in the driveshaft you can use CV joints with a 45* max operating angle which blows a U joint's max operating angle of 3* out of the water.

    There are several companies offering high angle CVs now for some time, but none of them are designed for constant use. When a CV has to run at high angles, those little crosses have to see-saw, back and forth, within the yokes at very high speed. There isn't very much grease in those trunnions to begin with, and the heat thats created from rapid rocking turns that grease into liquid that will eventually burn, losing it's lubricity in the process. At that stage, it's not long before the trunnion bearings fail and the CV fails.

    Believe me, I've extensively researched this for years, trying to find a solution. I spent several hours on the phone with several manufacturers including Tom Woods on their high angle CVs. Even looked into agriculture CV joints, and no one would recommend a CV at high angle to handle constant use. Sure they could be used and some ag joints could run at nearly 90*, but they couldn't do it for very long.

    To give you a bit of back story, I'll admit I was building something a bit more extreme than our OP's build. My RC was lifted 13 inches (10 suspension, 3 body) to clear 46" Michelin military tires. I stuck a Cummins in it, Dana 60/70s, and I was running a 727 with a divorced 205. That made for a really short rear shaft with a really steep angle. I did drop the tailshaft about three inches, and a further two inches on the t-case, and still the angle was rather steep. I talked to a local driveshaft shop who was building custom shafts for high rollers, and decided to try an experiment. We went with a Rzeppa style CV joint that was designed for a 70s era Eldorado. They were the largest joint we could find of this type, and the idea for using was, these joints carry a lot more grease to help keep them cool, but of course, there was no guarantee that it was going to work.

    I never got to try it out, The project stalled and never got restarted. Eventually, my Dakota needed some serious attention and I had to address that, and then we found some beautiful property and decided to move. So, long story short, I combined the RC project with my Dakota, dropped tire size, went with a more conventional drivetrain configuration, a longer wheel base, and now I have virtually zero rear d-shaft angle.

    Ed

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    Re: Required lift for 42" tires
    « Reply #16 on: November 15, 2020, 11:44:28 am »
    ...while pretty extreme, another option...and I know it works because I have done it...is using rockwell axles, which have the massive benefit of the pinion being 7 inches higher than a Dana axle, dramatically reducing the driveline angles.  The catch is...everything about rockwells is "huge" - "massive" - "need more shop equipment to move them around" -...and, "custom" (if you want to do it right and still be fairly safe,...and reliable). 

    I put rockwells and 46's under a 70's crewcab - a truck I wish I could have kept, but wow did that machine crawl over...well...everything.  With the tire size and chassis mods you're considering...well rockwells might just be legit for your build...just be prepared to have built a monster truck in the end before buying anything, oh and you'll need a BIG tow truck and BIG trailer to haul it anywhere not 'local'.

    This truck had about 12 inches of lift (4 in the suspension, ~8 in the custom body mounts), which ended up being perfect for both the tire size and wheel base, AND...yes I clocked both the front and rear axles up to zero out the driveline angle(s) into the diffs.







    If you haven't seen this thread, with the tire size you're considering this might glean a lot of helpful info -

    https://ramchargercentral.com/mopar-trucks/b-u-d-'78-m-350-(-need-some-shoes-)/1500/

    - Sam
    « Last Edit: November 15, 2020, 02:39:32 pm by Mad Max »
    2002 Dakota Quad Cab 4x4 - 440/46rh/Atlas4/D60/14b/40s
    2007 Cummins Ram 3500 Megadually 4x4 "Big Mack" - 5.9/G56 6-speed
    2016 Durango Citadel AWD - 5.7 Hemi/8-spd auto
    1952 Willys M-38 "Poncho"

                    .there's always a way...

                           ...Molon Labe...

    Offline 712edf

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    Re: Required lift for 42" tires
    « Reply #17 on: November 15, 2020, 02:27:18 pm »
    Rockwell = Big deep pockets too.

    Been there.

    But oh how they work.

    Bucky
    1975 W600   318  NP540  T223Rockwell tcase, Rockwell front & rear axles, 6.8 ratio

    Offline RXT

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    Re: Required lift for 42" tires
    « Reply #18 on: November 15, 2020, 05:17:12 pm »
    Rockwells could be a possible option (so can Portals) but to run Rocks, you almost have to run tires over 44s and you'll need overdrive because those axles came with a very short 6:72 ratio. Most 12V engines came from the factory governed at about 2600-2800 rpm and with those 6:72s you'll be against the redline if you try to run it on the highway. You can change the gov spring and get more rpms, but these engines pull much better at lower rpm. The sweet spot is around 1800 rpm even with higher gov speed

    With 40s and a 6:72 ratio if you're doing 55 mph, the engine will be spinning at 2772 rpm in 3rd and 1913 rpms in OD....At 70 mph the engine will be spinning at 3528 rpms and 2434 rpms in OD. I can tell you that the engine is going to sound very unhappy and fuel economy will plummet.

    I read somewhere about a 4:30 ratio being made available for the Rockwell top loaders, but I can't tell you if they were ever offered or if they exist at all, but it would open up the option to run 40s with a low rpm engine, like the 6BT

    Ed
    If we lose freedom here, there is no place to escape to. This is the last stand on Earth.

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    Re: Required lift for 42" tires
    « Reply #19 on: November 15, 2020, 05:31:06 pm »
    I think he's looking to run a big block, but yes Ed you're def right about the rpm's and a diesel.  I ran a 6BT Cummins and a 47RH and it topped out right around 65 mph, and that was with a fairly stock pump and 46" tires...
    2002 Dakota Quad Cab 4x4 - 440/46rh/Atlas4/D60/14b/40s
    2007 Cummins Ram 3500 Megadually 4x4 "Big Mack" - 5.9/G56 6-speed
    2016 Durango Citadel AWD - 5.7 Hemi/8-spd auto
    1952 Willys M-38 "Poncho"

                    .there's always a way...

                           ...Molon Labe...

    Offline u2slow

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    Re: Required lift for 42" tires
    « Reply #20 on: November 15, 2020, 06:12:50 pm »
    I would prefer to work within the lift/angle confines of the OE 1410 double-cardan joint (for the rear). Advertised at 22*, but as 'blocky' as it looks, I do wonder if it can be clearanced some.

    https://www.drivetrainamerica.com/neapco-n924141g-dodge-ram-1410-cv-head-asmbl/

    Build the rig around this constraint, see how tall you can go, and what size tires it lets you run.

    IMHO, deciding on tires 'first' when you've already chosen the truck, powertrain, and axles doesn't make the most sense.
    DD: 90 D250 6BT|5spd|D60/3.54/Lockright
    Tow/haul: 93 W250 Club 6BTA|5spd|D60/80/3.54/Lockright|4" lift|35's|HX35|5x.012s|4" pipe
    Projects: '84 D250 Ramcharger (cummins); '90 W250 Ramcharger (360TBI)
    Hers: 2005 Jeep Liberty V6|6spd|3.73/Trac-lok |3" lift, 245/75R16E Nokians

    Offline RXT

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    Re: Required lift for 42" tires
    « Reply #21 on: November 15, 2020, 07:16:52 pm »
    I think he's looking to run a big block,

    Looks to me that he's using a Cummins  ;D

    ....I was planning to swap the 360 for a 440, that fell through but I just purchased a 92 diesel 4x4 that has everything I need to swap in the 5.9 and the Dana 70/60 axles.

    Ed
    If we lose freedom here, there is no place to escape to. This is the last stand on Earth.

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    Offline Signguy97

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    Re: Required lift for 42" tires
    « Reply #22 on: November 18, 2020, 12:40:48 pm »
    Thanks so much for all the great info guys. I am balls deep into this project now, the ramcharger is down to the bare frame, pulling the body off was way easier than I imagined! I yanked the 5.9 out of the truck yesterday, and will pull the axles today.
    I'm going to bolt up the 5.9 to the 727/205 combo I purchased and have a look at everything with it sitting in the ramcharger frame, as far as I can see it looks like it is just going to bolt straight in. I think the only extra suspension lift I'm going to have to deal with is the extra 1-1/2" or so that I'm going to get from installing the Dana 60 in the front. Since the front end will now be part time I'm thinking if I can figure out a driveshaft that will work without binding( even if I have to go to a cv ) it will probably last ok because it will only be in use while I'm off-road. This new setup will actually be 6" shorter at the rear, using the 205 instead of the 203, so hopefully the rear driveshaft won't be too much of an issue.
    As I meantioned, I was going to change the gearing to 4:88, I was thinking of trying an Eaton true-track in the rear and possibly the front, just wondered what you guys thought of that idea.

    Offline u2slow

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    Re: Required lift for 42" tires
    « Reply #23 on: November 18, 2020, 02:09:40 pm »
    Hmmm.... Cummins, 727, and 4.88. 

    I wouldn't get into re-gearing anything until your tire size is finalized. Moreover, the 3.07 diffs are tougher to re-gear than the std ones. The torsen devices have a mixed following. Be sure you know what you're signing up (paying) for. My buddy swapped his out for a Grizzly. For my money & use (and daily driving) a lunchbox locker is a good value. (No-slip, Lockright, Spartan, etc.)
    DD: 90 D250 6BT|5spd|D60/3.54/Lockright
    Tow/haul: 93 W250 Club 6BTA|5spd|D60/80/3.54/Lockright|4" lift|35's|HX35|5x.012s|4" pipe
    Projects: '84 D250 Ramcharger (cummins); '90 W250 Ramcharger (360TBI)
    Hers: 2005 Jeep Liberty V6|6spd|3.73/Trac-lok |3" lift, 245/75R16E Nokians

    Offline Signguy97

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    Re: Required lift for 42" tires
    « Reply #24 on: November 18, 2020, 07:02:21 pm »
    Hmmm.... Cummins, 727, and 4.88. 

    I wouldn't get into re-gearing anything until your tire size is finalized. Moreover, the 3.07 diffs are tougher to re-gear than the std ones. The torsen devices have a mixed following. Be sure you know what you're signing up (paying) for. My buddy swapped his out for a Grizzly. For my money & use (and daily driving) a lunchbox locker is a good value. (No-slip, Lockright, Spartan, etc.)

    Tire size is finalized, I have already purchased 42" goodyears, not sure what you mean by 3.07sthe ones I have are 3.55, would you suggest something different with my combo in the way of a gear ratio?

    Offline u2slow

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    Re: Required lift for 42" tires
    « Reply #25 on: November 18, 2020, 07:41:39 pm »
    Tire size is finalized, I have already purchased 42" goodyears, not sure what you mean by 3.07sthe ones I have are 3.55, would you suggest something different with my combo in the way of a gear ratio?

    All (most?) Cummins/727 trucks came with 3.07 diffs that aren't easily re-geared.... that's all. Worth checking again? Guys with that setup typically struggle with highway speeds and run larger tires to compensate.

    If you have 3.55, I would plan on trying it out. 4.10 might be enough for a re-gear.
    DD: 90 D250 6BT|5spd|D60/3.54/Lockright
    Tow/haul: 93 W250 Club 6BTA|5spd|D60/80/3.54/Lockright|4" lift|35's|HX35|5x.012s|4" pipe
    Projects: '84 D250 Ramcharger (cummins); '90 W250 Ramcharger (360TBI)
    Hers: 2005 Jeep Liberty V6|6spd|3.73/Trac-lok |3" lift, 245/75R16E Nokians

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    Re: Required lift for 42" tires
    « Reply #26 on: November 18, 2020, 08:39:49 pm »
    ...I may be missing something, but just to make sure, your donor driveline is a 92 CTD 6BT, 46RH (overdrive) trans, NP205 t-case, and the associated front D60 and rear D70, correct?  If so, like I was saying before, my last truck has 6.72 gears, 46" tires, and would do 65 mph at ~2300 rpm - which is a good 'sweet spot' for a 1st gen 6BT like yours.  But, you're running 42's, and with 5.38s you'll be running 70 mph right around 2000 rpm, which is really good.  4.88s would bring 70 mph down to about 1850 rpm - a bit low.  So, if you're wanting to cruise the highway at all then 5.38s are what I'd suggest.

    Also, what kind of Goodyears - military tires, or MTR's, other?
    « Last Edit: November 18, 2020, 08:41:46 pm by Mad Max »
    2002 Dakota Quad Cab 4x4 - 440/46rh/Atlas4/D60/14b/40s
    2007 Cummins Ram 3500 Megadually 4x4 "Big Mack" - 5.9/G56 6-speed
    2016 Durango Citadel AWD - 5.7 Hemi/8-spd auto
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    Offline u2slow

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    Re: Required lift for 42" tires
    « Reply #27 on: November 18, 2020, 09:33:10 pm »
    I'm going to bolt up the 5.9 to the 727/205 combo I purchased and have a look at everything with it sitting in the ramcharger frame, ...
     I was going to change the gearing to 4:88

    So does this build use a 727 or the overdrive A518?  That's what's thrown me for a loop....  ???
    DD: 90 D250 6BT|5spd|D60/3.54/Lockright
    Tow/haul: 93 W250 Club 6BTA|5spd|D60/80/3.54/Lockright|4" lift|35's|HX35|5x.012s|4" pipe
    Projects: '84 D250 Ramcharger (cummins); '90 W250 Ramcharger (360TBI)
    Hers: 2005 Jeep Liberty V6|6spd|3.73/Trac-lok |3" lift, 245/75R16E Nokians

    Offline RXT

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    Re: Required lift for 42" tires
    « Reply #28 on: November 19, 2020, 06:22:12 am »
    Thanks so much for all the great info guys. I am balls deep into this project now, the ramcharger is down to the bare frame, pulling the body off was way easier than I imagined! I yanked the 5.9 out of the truck yesterday, and will pull the axles today.
    I'm going to bolt up the 5.9 to the 727/205 combo I purchased and have a look at everything with it sitting in the ramcharger frame, as far as I can see it looks like it is just going to bolt straight in. I think the only extra suspension lift I'm going to have to deal with is the extra 1-1/2" or so that I'm going to get from installing the Dana 60 in the front. Since the front end will now be part time I'm thinking if I can figure out a driveshaft that will work without binding( even if I have to go to a cv ) it will probably last ok because it will only be in use while I'm off-road. This new setup will actually be 6" shorter at the rear, using the 205 instead of the 203, so hopefully the rear driveshaft won't be too much of an issue.
    As I meantioned, I was going to change the gearing to 4:88, I was thinking of trying an Eaton true-track in the rear and possibly the front, just wondered what you guys thought of that idea.

    With the combination of parts you're using, you'll find that the truck will be barely drivable on the road. Sure, it could be done for driving around town but it will seem like you're driving around in low range. Whats going to hurt are those 4:88s and lack of OD. And you may want to take a close look at that Dana 60 front you're planning on using. If it's really a Dana 61, it's going to be a lot harder to regear to 4:88.

    If you want to be able to drive this truck on the road and occasionally on the highway, you need a trans with OD, maybe a 47RH or NV4500, and you'll need to gear the axles a bit higher, like 4.56. And consider radials.

    Ed
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    Re: Required lift for 42" tires
    « Reply #29 on: November 19, 2020, 09:08:49 am »
    my bad - I keep missing nuggets of info.  Okay so if you have a 'Cummins' 727/205 combo - that were behind the 89-91.5 CTD 4x4 trucks (be sure the converter has the 6-bolt setup and not a 4-bolt (gassers were 4 bolt, Cummins were 6), if so then you do not have an overdrive, and depending on whether or not you want to do much street driving/highway driving...well you likely won't 'need' an overdrive.  With 4.10's and 42's 65 mph is right around 2100 rpm - not bad. 

    With that much gearing tho you will need a very good cooling system and the torque converter will really be getting a workout.  A Cummins can make the torque required to move a heavy truck on 42's, but the torque converter is what gets the torque to the tires, and without the really deep gears it's gonna be getting pretty hot so you'll need two or three coolers - factory pickups had 2 with a 3rd under the bed as a dealer-installed option.

    Also, those early Cummins 727s did not have overdrive or lockup, so your converter selection will be really critical, and it's a very fine line between having a high enough stall to 'get going/around town' and low enough stall for sustained driving.
    2002 Dakota Quad Cab 4x4 - 440/46rh/Atlas4/D60/14b/40s
    2007 Cummins Ram 3500 Megadually 4x4 "Big Mack" - 5.9/G56 6-speed
    2016 Durango Citadel AWD - 5.7 Hemi/8-spd auto
    1952 Willys M-38 "Poncho"

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    Offline Signguy97

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    Re: Required lift for 42" tires
    « Reply #30 on: November 19, 2020, 12:06:43 pm »
    my bad - I keep missing nuggets of info.  Okay so if you have a 'Cummins' 727/205 combo - that were behind the 89-91.5 CTD 4x4 trucks (be sure the converter has the 6-bolt setup and not a 4-bolt (gassers were 4 bolt, Cummins were 6), if so then you do not have an overdrive, and depending on whether or not you want to do much street driving/highway driving...well you likely won't 'need' an overdrive.  With 4.10's and 42's 65 mph is right around 2100 rpm - not bad. 

    With that much gearing tho you will need a very good cooling system and the torque converter will really be getting a workout.  A Cummins can make the torque required to move a heavy truck on 42's, but the torque converter is what gets the torque to the tires, and without the really deep gears it's gonna be getting pretty hot so you'll need two or three coolers - factory pickups had 2 with a 3rd under the bed as a dealer-installed option.

    Also, those early Cummins 727s did not have overdrive or lockup, so your converter selection will be really critical, and it's a very fine line between having a high enough stall to 'get going/around town' and low enough stall for sustained driving.



    Ok more good info, in the last few posts, and once again I'm new at this so bare with me , I've been restoring old corvettes all my life but this 4x4 stuff is a different ball game. You guys are throwing some numbers at me that have no meaning to me. I just checked the torque converter on the trans I have, it has six bolts, I'm assuming it is a three speed 727, I know for a fact that I have Dana 60( not 61)/70 axles, and I know for sure they have 3.55 gears in them.
    I certainly don't think I can run the 3.55s and I know the carrier split is 4.10 and down and 456 and up, as I will be putting some type of locker in the back anyway I might as well put the optimum gear ratio in there, and going by a chart online it shows me that 4.88 will give me around 2400 rpm at 65 miles per hour. I can get my hands on 727 with overdrive , but are they not longer, I'm dealing with the short driveline angles already.

    Offline Signguy97

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    Re: Required lift for 42" tires
    « Reply #31 on: November 19, 2020, 12:18:03 pm »
    The tires I have are Goodyear, MTRs 42" x 14.5, 17

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    Re: Required lift for 42" tires
    « Reply #32 on: November 19, 2020, 12:38:47 pm »

    You guys are throwing some numbers at me that have no meaning to me

    no worries - let us know what questions you have and we'll help get you squared away as best we can
    2002 Dakota Quad Cab 4x4 - 440/46rh/Atlas4/D60/14b/40s
    2007 Cummins Ram 3500 Megadually 4x4 "Big Mack" - 5.9/G56 6-speed
    2016 Durango Citadel AWD - 5.7 Hemi/8-spd auto
    1952 Willys M-38 "Poncho"

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    Offline RXT

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    Re: Required lift for 42" tires
    « Reply #33 on: November 19, 2020, 09:11:22 pm »


    Ok more good info, in the last few posts, and once again I'm new at this so bare with me , I've been restoring old corvettes all my life but this 4x4 stuff is a different ball game. You guys are throwing some numbers at me that have no meaning to me.

    Different is always good. Which numbers are not making sense to you. If it's anything I've mentioned, I will try to explain better in detail.

     
    Quote
    I just checked the torque converter on the trans I have, it has six bolts, I'm assuming it is a three speed 727,

    What you need to know is the Torqueflite 727 is a three speed transmission with no over drive and no lock up torque converter. There is a very specific version of the 727 that is used behind the Cummins. These Cummins specific 727s have a unique bell housing which only fits the Cummins. No other version of the 727 will bolt up. Naturally it should have 6 bolts. Be certain you have one of these Cummins specific 727s

    Quote
    I know for a fact that I have Dana 60( not 61)/70 axles, and I know for sure they have 3.55 gears in them.
    I certainly don't think I can run the 3.55s.......and going by a chart online it shows me that 4.88 will give me around 2400 rpm at 65 miles per hour.

    Those charts do not take into account the unique abilities and requirements of Diesel engines. Unlike gas engines, diesels do not have as broad an rpm range. For example, you can rev a gas engine 4000-6000 rpm or more. However a diesel, like your 6BT Cummins is governed at about 2200 rpm where it begins to de-fuel. So based on the chart, your truck will never reach 65mph because you need the engine to spin at 2400rpm and it can't spin past 2200rpm because of the governor. You can change the governed rpm by installing a 3200GSK (3200rpm governor spring kit) and this should allow an rpm which will exceed 2400rpm and allow the truck to reach 65mph, but you really don't want to run a diesel against it's redline. The 3200gsk is better suited to allowing higher rpm shifts rather than continual operation.

    Those charts aren't as useful for diesels. However diesels like your Cummins can make tons of torque. When Chrysler began offering the Cummins in 89, they had to make some compromises. Automatics were always a popular option, but at the time, the only automatic transmission available was the 727. If they used the same axle ratios and tire sizes as the gas powered trucks, they couldn't make highway speed because the engines couldn't rev past 2200rpm. What was needed was a transmission with over drive. but the 727 didn't have one and it was going to take time to develop one. So they compromised. They went with axles equipped with 3.07 gears to provide some over drive effect and it was enough to get them to reach highways speed, but not much more. The engine had more than enough torque to turn the factory 30" tall tires with that tall 3.07 ratio gear but the torque converter had to slip to get going and slip creates heat. To counteract the slip induced heat, all Cummins trucks were equipped with a block mounted heat exchanger and an additional -rather large trans cooler, with an optional "Super Cool" option which added another trans cooler with it's own fan which was mounted under the bed.

    Technically you could run those 3:55s and 40 inch tires if you turn up the wick (Turn up the HP and torque) but that transmission will be punished hard due to how much the torque converter will have to slip to get the truck going. A 4:11 with 40s would be a close match to the factory 3.07 with 30" treads, but in all honesty you're living with that original compromise.

    Quote
    I can get my hands on 727 with overdrive , but are they not longer, I'm dealing with the short driveline angles already.

    You can't, as mentioned, the 727 has to be Cummins specific. Your options are either you live with the 727 you have (assuming it's Cummins specific) and avoid highways, or look for a Cummins specific transmission with over drive.

    Ed
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    Offline Signguy97

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    Re: Required lift for 42" tires
    « Reply #34 on: November 20, 2020, 11:57:01 am »
    Ok thanks for that detailed reply, all of this is starting to make me think I should just install the five speed standard trans/205 combo that is in my doner truck, I get what your saying 2400 would be pushing the limits of the diesel, I have actually installed the performance fuel pin and governor spring, I did that before I pulled the motor and it made a huge difference in power. What automatic transmissions will work with the cummins/205 that I have?

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    Re: Required lift for 42" tires
    « Reply #35 on: November 20, 2020, 12:24:29 pm »
    as far as what transmissions will bolt up clean, the 'Cummins' versions of each of these: 727 (89-91.5, non-overdrive or lockup), 518/46RH (91.5-93, overdrive, non-lockup, non-computer controlled), 47RH (94-95.5, overdrive, lockup, non-computer controlled - best overall trans IMPO), 47RE (96-up, OD, LU, computer-controlled...unless you install a full manual valve body and other voodoo) - each will require the matching factory block-to-bellhousing adapter.
    2002 Dakota Quad Cab 4x4 - 440/46rh/Atlas4/D60/14b/40s
    2007 Cummins Ram 3500 Megadually 4x4 "Big Mack" - 5.9/G56 6-speed
    2016 Durango Citadel AWD - 5.7 Hemi/8-spd auto
    1952 Willys M-38 "Poncho"

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    Offline RedneckInTraining

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    Re: Required lift for 42" tires
    « Reply #36 on: November 20, 2020, 12:44:56 pm »
    There are several companies offering high angle CVs now for some time, but none of them are designed for constant use. When a CV has to run at high angles, those little crosses have to see-saw, back and forth, within the yokes at very high speed. There isn't very much grease in those trunnions to begin with, and the heat thats created from rapid rocking turns that grease into liquid that will eventually burn, losing it's lubricity in the process. At that stage, it's not long before the trunnion bearings fail and the CV fails.



    Believe me, I've extensively researched this for years, trying to find a solution. I spent several hours on the phone with several manufacturers including Tom Woods on their high angle CVs. Even looked into agriculture CV joints, and no one would recommend a CV at high angle to handle constant use. Sure they could be used and some ag joints could run at nearly 90*, but they couldn't do it for very long.
    To give you a bit of back story, I'll admit I was building something a bit more extreme than our OP's build. My RC was lifted 13 inches (10 suspension, 3 body) to clear 46" Michelin military tires. I stuck a Cummins in it, Dana 60/70s, and I was running a 727 with a divorced 205. That made for a really short rear shaft with a really steep angle. I did drop the tailshaft about three inches, and a further two inches on the t-case, and still the angle was rather steep. I talked to a local driveshaft shop who was building custom shafts for high rollers, and decided to try an experiment. We went with a Rzeppa style CV joint that was designed for a 70s era Eldorado. They were the largest joint we could find of this type, and the idea for using was, these joints carry a lot more grease to help keep them cool, but of course, there was no guarantee that it was going to work.



    Ed



    When I say CV I mean constant velocity joints like on fwd cars or new military trucks, Not double cardan "CV" joints. https://www.walterscheid-group.com/wp-content/uploads/UC-02-GB-0319_web.pdf
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    Offline u2slow

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    Re: Required lift for 42" tires
    « Reply #37 on: November 20, 2020, 01:04:33 pm »
    Ok thanks for that detailed reply, all of this is starting to make me think I should just install the five speed standard trans/205 combo that is in my doner truck,

    Agreed  8)
    DD: 90 D250 6BT|5spd|D60/3.54/Lockright
    Tow/haul: 93 W250 Club 6BTA|5spd|D60/80/3.54/Lockright|4" lift|35's|HX35|5x.012s|4" pipe
    Projects: '84 D250 Ramcharger (cummins); '90 W250 Ramcharger (360TBI)
    Hers: 2005 Jeep Liberty V6|6spd|3.73/Trac-lok |3" lift, 245/75R16E Nokians

    Offline RXT

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    Re: Required lift for 42" tires
    « Reply #38 on: November 20, 2020, 05:16:51 pm »
    Ok thanks for that detailed reply, all of this is starting to make me think I should just install the five speed standard trans/205 combo that is in my doner truck, I get what your saying 2400 would be pushing the limits of the diesel, I have actually installed the performance fuel pin and governor spring, I did that before I pulled the motor and it made a huge difference in power. What automatic transmissions will work with the cummins/205 that I have?

    Sam (aka Mad Max) has pretty much outlined which Chrysler automatics will work, but to clarify further, besides the transmissions, there are also two different trans adapters. The 727 trans adapter will not work with the 47RH & E. The difference is the lock up torque converter. Lock up TCs are physically thicker, so they require a deeper trans adapter. BTW there are also trans adapters for GM and Ford automatics as well as a universal SAE #2 adapter. That means you could use an Allison, HD Ford if you want or any number of medium duty transmissions like Eaton-Fuller, Spicer, Road Ranger etc. The only limiting factor is getting a transfer case behind them.

    I currently have a Dakota with a Cummins and a 47RE. I found the 47RE in the junk yard, in a 98 Ram 3500 4x4 which had a V10 Magnum (The only other engine which shares the Cummins bell pattern) 47REs are computer controlled, ideally 47RH are not computer controlled but they are much harder to find (only available for two model years) and far more desirable. However, 47REs are more common and no one really wants them and as far as I know, there wasn't a stand alone computer. (I picked up mine for under $100) It's possible to run a 47RE without the computer if you're willing to shift it manually. And thats what I did with mine. A 47RH manual valve body will work in a 47RE. All you have to do after the MVB swap is wire in two toggles to engage and disengage the Lock up TC and over drive. And in my case, since I started with a 47RE out of a V10, the gas engine torque converter was replaced with a diesel torque converter

    When I say CV I mean constant velocity joints like on fwd cars or new military trucks, Not double cardan "CV" joints. https://www.walterscheid-group.com/wp-content/uploads/UC-02-GB-0319_web.pdf

    OK. The "Official" name for that style or type of CV is called a Rzeppa joint. And if you re-read my post that you just replied to, you will read that this was the same type of joint I was experimenting with and installed in my rear driveshaft.

    My reason to give it a shot was to see if the greater volume of grease would reduce the chance of frying the grease, but Rzeppa joints also produce much more friction than a double cardan, because they rely on several large ball bearings which must slide along grooves within the joint. I was gambling that there was more than enough grease to cancel the heat generating friction and last longer

    In the end, after much research and talking to manufacturers who wouldn't guarantee that the joint would last in continuous high angle service, I had concluded that there is no joint that would last long. They can certainly handle very short duration high angle use, but the problem is every joint has moving parts that has to cycle thousands of times when operating at an angle. Some joints produce high frictional loads and some have rotating parts. To complicate all this, they live in an extreme environment, resisting large torque loads and dirt, dust, sand, and mud.

    I even researched very expensive and experimental joints, such as the Bigelow CV joint and Thompson joint, to no avail.

    Ed
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    Offline Signguy97

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    Re: Required lift for 42" tires
    « Reply #39 on: November 22, 2020, 05:51:55 pm »
    Thanks for all the advise here guy, what I am going to try is using the stuff I have, and yesterday I found a 78 ramcharger with some beautiful rebuilt Dana 60,s with 4.10 gears, I'm going to try the cummins with the 727/ 205 combo that I bought, the 4.10s with the 42" tires is going to give me almost exactly the same ratio as what I had in the truck with the 360 / 727 /203 combination running 37" ( actually only measured 35") tires , and that worked quite well, it will be spinning around 2300 at 65, but most of my driving would be 60 mph max so hopefully it will work out, I'll keep my eye out for a four speed auto, and can always swap it out in the future and lower the gearing.
    Anyways, got a little off topic on the required lift for the 42"s but I've gained some good info , thank you!

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    Re: Required lift for 42" tires
    « Reply #40 on: November 22, 2020, 07:43:35 pm »
    sounds like a plan.  One thing - the 205 has a lousy 'low range' - it's only 1.96-1, which will leave a lot to be desired when crawling around off road.  I'm not certain, but I think places like Advanced Adapters and Northwest Fab and Offroad Design make similar but different versions of a 'doubler' box that would bolt up between your 727 and the 205, which would really improve the truck's off road low range manners, not to mention gaining the ability to twin-stick the 205 and other perks.  Just food for thought
    2002 Dakota Quad Cab 4x4 - 440/46rh/Atlas4/D60/14b/40s
    2007 Cummins Ram 3500 Megadually 4x4 "Big Mack" - 5.9/G56 6-speed
    2016 Durango Citadel AWD - 5.7 Hemi/8-spd auto
    1952 Willys M-38 "Poncho"

                    .there's always a way...

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