rob904x4
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« on: March 8, 2010, 08:33:47 PM » |
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ok heres the story i bought a 91 ctd with a getrag 5 speed and i also bout an 86 ramcharger and did the motor swap so now i have a running 86 ramcharger with a ctd the only problem is its a 2wd and i think* the gears it has is 410 now with that being said the factory tire size is 235/85/16 with a overall diameter of 31.72in im now running 235/55/17 with an overall diameter of 27.17in so that alittle smaller the problem i am having is the truck runs out of gear about 70 mph i dont know how much exactly because my speedo doesnt work but what gears should i be runnig so i could aleast get up to about a 100 and still be happy any info would be great |
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p/s intercooler, hx35 turbo, denny t stag 2 fuel pin, pump turned in three turns ,gsk,three piece manifold,pensacola diesel injectores,2nd gen intake elbow,4" mandrel bent exhaust
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mopar65pa
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« Reply #1 on: March 8, 2010, 08:54:30 PM » |
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Look to the left hand side of the page, go down till you see calculators, plug in you #'s there and it will give you and RPM you are at at what speed. I would go with a 265/75/16 tire if I were you. My 90 CTD is running 2035rpms at 65mph.  You should be at 1437rpms at 65mph if I am figuring it right.  |
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I'd rather push a DODGE than drive a chevy or a ford!!!!!! 78 D200 Crew Cab 93 Shadow SE V6 77 400/727 RC 79 360/727 RC 89 318/727 RC 80 318/435 TD 90 CTD W250 73 Charger SE 400/727 |
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440 4spd Power Ram
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« Reply #2 on: March 8, 2010, 08:56:00 PM » |
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What rear axle did you use? The stock RC axle could be a 8-1/4 or 9-1/4 with anything from 2.71-3.91 gears.
CTD 5spd with 235s would be happy with 3.21s I would think.
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mopar65pa
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« Reply #3 on: March 8, 2010, 09:13:51 PM » |
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What rear axle did you use? The stock RC axle could be a 8-1/4 or 9-1/4 with anything from 2.71-3.91 gears.
CTD 5spd with 235s would be happy with 3.21s I would think.
The 91 that I bought for the frame was a CTD 5 speed with 4:10's From the "graph" I saw the CTD like to be in the 1800-1900 rpm range for prime MPGs and power. I would have to drive mine at 57mph to be in that range.  Like that's gonna happen!  |
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I'd rather push a DODGE than drive a chevy or a ford!!!!!! 78 D200 Crew Cab 93 Shadow SE V6 77 400/727 RC 79 360/727 RC 89 318/727 RC 80 318/435 TD 90 CTD W250 73 Charger SE 400/727 |
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440 4spd Power Ram
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« Reply #4 on: March 8, 2010, 09:21:10 PM » |
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Having owned a '90 CTD 5spd with 4.10s I can say they need more gear..  What you really need is the rear axle from a CTD 727, 3.07 gears+ overdrive= 100 MPH easy.. |
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mopar65pa
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« Reply #5 on: March 8, 2010, 09:33:12 PM » |
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Having owned a '90 CTD 5spd with 4.10s I can say they need more gear.. What you really need is the rear axle from a CTD 727, 3.07 gears+ overdrive= 100 MPH easy.. Yeah then you are out of the power/torque range though. |
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I'd rather push a DODGE than drive a chevy or a ford!!!!!! 78 D200 Crew Cab 93 Shadow SE V6 77 400/727 RC 79 360/727 RC 89 318/727 RC 80 318/435 TD 90 CTD W250 73 Charger SE 400/727 |
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SuperBurban
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« Reply #6 on: March 8, 2010, 09:36:39 PM » |
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A close ratio od/dd/ud aux gear box.  |
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RollingBombShelter
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« Reply #7 on: March 8, 2010, 09:47:03 PM » |
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Yeah then you are out of the power/torque range though. Not to mention the fact that with the aerodynamics of a billboard, at that speed you will create a rift in the space-time continuum.  |
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mopar65pa
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« Reply #8 on: March 8, 2010, 09:50:50 PM » |
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Not to mention the fact that with the aerodynamics of a billboard, at that speed you will create a rift in the space-time continuum. LOL......... |
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I'd rather push a DODGE than drive a chevy or a ford!!!!!! 78 D200 Crew Cab 93 Shadow SE V6 77 400/727 RC 79 360/727 RC 89 318/727 RC 80 318/435 TD 90 CTD W250 73 Charger SE 400/727 |
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rob904x4
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« Reply #9 on: March 8, 2010, 10:45:09 PM » |
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well i cant run a bigger tire because im useing the stock half ton springs up front and have the rear lowered a bit so bigger tires are out of the question http://s125.photobucket.com/albums/p45/rob904x4/?action=view¤t=jay012.jpg&newest=1 this is a pic befor i lowered the rear i was thinking 321 gears but not sure |
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p/s intercooler, hx35 turbo, denny t stag 2 fuel pin, pump turned in three turns ,gsk,three piece manifold,pensacola diesel injectores,2nd gen intake elbow,4" mandrel bent exhaust
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rob904x4
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« Reply #10 on: March 8, 2010, 10:47:51 PM » |
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the axle i have under the ramcharger is an 8 lug 9 1/4 out of a 90 3/4 gasser old city truck
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p/s intercooler, hx35 turbo, denny t stag 2 fuel pin, pump turned in three turns ,gsk,three piece manifold,pensacola diesel injectores,2nd gen intake elbow,4" mandrel bent exhaust
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440 4spd Power Ram
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« Reply #11 on: March 8, 2010, 10:54:39 PM » |
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the axle i have under the ramcharger is an 8 lug 9 1/4 out of a 90 3/4 gasser old city truck
If you want to keep the 9-1/4HD you can go as high as 2.94 or 2.76, most 9-1/4HDs are 3.55 or 3.91. |
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s ǝoɾ
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« Reply #12 on: March 9, 2010, 12:58:09 AM » |
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3.42 (american axle) will get you 100mph at just over 3000. 3.54/55 (dana or corp) will get you a little higher in the rpm range. No big deal since I highly doubt you are cruising there, maybe just a few (less than 15?) second bursts?
3.21 puts you at ~1800 rpms @ 65mph and around 2900 @100mph.
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Avoid replacing any part that you have not proven to be faulty through extensive testing. |
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magnumRC
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« Reply #13 on: March 9, 2010, 09:17:04 AM » |
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I have stock 3.21 gears and an NV 4500 5 speed and I can go 77mph max in 4th gear. That's with a 92 motor and 33x12.50 tires.
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83 Ramcharger w/92 Cummins, NV4500, NP208, D44/ 9.25 axles, 3\" lift, turned up VE pump (mild).
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rob904x4
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« Reply #14 on: March 9, 2010, 08:21:21 PM » |
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so does everyone think i should go with 321?  with the tires im running |
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p/s intercooler, hx35 turbo, denny t stag 2 fuel pin, pump turned in three turns ,gsk,three piece manifold,pensacola diesel injectores,2nd gen intake elbow,4" mandrel bent exhaust
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s ǝoɾ
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« Reply #15 on: March 9, 2010, 08:31:38 PM » |
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Sounds good to me.
Understanding the fact that regardless, 100mph is still approx 3000rpms, so you will need to have the power at that rpm to counter windspeed.
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magnumRC
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« Reply #16 on: March 10, 2010, 10:01:45 PM » |
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If you really want to go 100mph you will have to go with even taller gears than 3.21 because the 91 motor is governed to around 2600rpm. It starts to defuel even sooner.
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83 Ramcharger w/92 Cummins, NV4500, NP208, D44/ 9.25 axles, 3\" lift, turned up VE pump (mild).
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s ǝoɾ
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« Reply #17 on: March 10, 2010, 10:10:31 PM » |
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Why not add a 366 gsk, and the appropriate fuel?
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sdstriper
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« Reply #18 on: March 11, 2010, 01:41:36 AM » |
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Calculate what r&p you need to get optimal rpm at freeway speeds. 1800-2200 rpm.
And you would not regret the gov' spring upgrade.
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89' D250 CTD, 727HD, D70/3.07, Tweaked VE, 4" exhaust, usual suspect gauges...
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magnumRC
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« Reply #19 on: March 11, 2010, 01:30:53 PM » |
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Why not add a 366 gsk, and the appropriate fuel?
Good idea. Changing the gov spring is surely easier and cheaper than changing diff gears. Be conservative with the fuel on the 9 1/4. I haven't blown mine up yet, but as soon as I get 3/4 ton axles ready to install it's going to be black smoke and 9 1/4 torture test to see what it can take. |
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83 Ramcharger w/92 Cummins, NV4500, NP208, D44/ 9.25 axles, 3\" lift, turned up VE pump (mild).
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rob904x4
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« Reply #20 on: March 11, 2010, 02:12:07 PM » |
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yeah i have the gsk and a denny t fuel pin but i know the spring can be a pain in the ass so i have been putting it off lol and i dont need to go 100 but if i ever on the freeway and someone wants to fuck with me i have alittle room to play with
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p/s intercooler, hx35 turbo, denny t stag 2 fuel pin, pump turned in three turns ,gsk,three piece manifold,pensacola diesel injectores,2nd gen intake elbow,4" mandrel bent exhaust
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rob904x4
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« Reply #21 on: March 20, 2010, 06:11:29 PM » |
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well i did the gsk and he fuel pin and what a difference it makes the spring wasnt even that bad and the fuel pin my grandmother could have done that.as it did give me more top end the gear problem is still to short im going wiht the 321's and hopefully i will be happy the 9.25 is holding up good for now
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p/s intercooler, hx35 turbo, denny t stag 2 fuel pin, pump turned in three turns ,gsk,three piece manifold,pensacola diesel injectores,2nd gen intake elbow,4" mandrel bent exhaust
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swdockter
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« Reply #22 on: March 20, 2010, 07:55:41 PM » |
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I'd be surprised if you don't already have 3.21 (3.23?) already in the factory axle. Very common gear set. Is there a tab on one of the bolts, they have the ration on it? If not just pull off the diff cover and count the teeth on the ring an pinion gears.
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88 Ramcharger 4x4 318 TBI rust free
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rob904x4
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« Reply #23 on: March 21, 2010, 09:15:43 AM » |
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well i hope your wrong because i already ordererd the 321 and there is no tag on the diff i already checked but looks like im going to count the teeth and do the math
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440 4spd Power Ram
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« Reply #24 on: March 21, 2010, 09:23:52 AM » |
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The 9-1/4 HD never came with anything higher than 3.55s, 90% of them are 3.91s. The half ton 9-1/4 in stock RCs and trucks 3.21 is most common.. |
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