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4BT transmission options?

42K views 33 replies 11 participants last post by  1973moneypit 
#1 ·
Joes diesel post got me wondering.

I want to swap the engine out of my 90 W150. I had thought before of a 6BT but dont want to for the cost and the weight. I looked into the 4BTs and they seemed a better candidate, lighter, better power and mileage then the 360 I have in there now or the 440 I day dreamed of putting in. So my web surfing brought up some questions.

Would the NP435 I havd in the truck now hold up and is there a bellhousing to adapt it? I believe it was 4BTswaps.com that stated it would not hold up to the torque even from a 4BT and it would be a poor choice for a candidate.

So the next option is the cost prohibitive and according to Novak's article on the 4500, its not really worth it.

So whats the best transmission to use with a 4BT if you still want a manual?

Is there a way to adapt what I have as far as drivetrain goes to the 4BT and make it work for a truck running 35in tires? What would the best gearing be? Steer clear or drive on with the 4.56s planned?

They ran the 241 in the cummins equipped trucks so I am confident that will hold. What else should I know or am not asking?
 
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#2 ·
A G360 from a first Gen Cummins will do fine behind a 4bt, a 435 can take the torque of a 4bt but the lack of overdrive would be the deal breaker there with 4.56s.
 
#3 ·
I got 3.55s now. Would that be better? I like my ol Np 435 and the more I look into swapping it the more I want to keep it.

Now if I didnt have to regear due to a diesel mil being able to run the RPM in such a way as to save from having to swap gears out... that would save the cost, easily 1500-2000 for gears to be done.
 
#6 ·
s ǝoɾ said:
Depends on how fast you like to push it on the highway. Should be 2200 in 4th, or there abouts at 65mph.

Haven't looked into the magical rpms that the 4bt likes to run.
Whats the realistic rev limits on the 4BT?

440 4spd Power Ram said:
I remember reading about a 4bt swap using a NP435 by redrilling a G360 bellhousing, but I can't recall if it was a Dodge or Ford 435 being used.. {think}
From what I am reading on 4btswaps looks like ford.
 
#8 ·
A 4bt is only 200lbs lighter than a 6bt and they cost about the same.  Quite often the 6bt is cheaper because there are so many of them around.

The huge advantages of the 4bt are the length and the load factor.  Cummins refused to offer Chrysler the standard 300k warranty on the 6bt because it is too much engine for the application.  Cummins was concerned with fuel wash, carbon, and cylinder scoring issues because the 6bt in a pickup wouldn't be worked hard enough.  The 4bt is the perfect size for a pickup.  Since it has to work harder in a pickup, it is much more efficient than the 6bt.

Shy away from the 435.  Find a 5-speed.  If you decide to keep the 435 I would change the input shaft to at least an 1 1/4" 10 spline shaft.  Clutches will be much easier to find it will be much stronger than the stock shaft.  You might even think of installing an auxiliary transmission to get more gears. 

 
#9 ·
440 4spd Power Ram said:
A G360 from a first Gen Cummins will do fine behind a 4bt, a 435 can take the torque of a 4bt but the lack of overdrive would be the deal breaker there with 4.56s.
You could add a Laycock / J-Type Overdrive unit (usually found in older Volvo's) behind the 435. Long time ago i recall reading about Mopar Guys using it behind the Transmission on Street/Strip cars so they could drive back and forth to the Track without swapping gears/chunks.
 
#10 ·
magnumRC said:
The huge advantages of the 4bt are the length and the load factor. Cummins refused to offer Chrysler the standard 300k warranty on the 6bt because it is too much engine for the application. Cummins was concerned with fuel wash, carbon, and cylinder scoring issues because the 6bt in a pickup wouldn't be worked hard enough. The 4bt is the perfect size for a pickup. Since it has to work harder in a pickup, it is much more efficient than the 6bt.
Soooo many fail to realize that. Keeping a diesel warm and loaded is very important.

It seems counter intuitive compared to gasoline engines, where a big 440 producing a lazy 200hp, is considered a reliability feature. Less cylinder pressure, less wear and heat so the story goes. In a diesel, less cylinder pressure and heat equals more piston slap, wider ring end gaps, more fuel in the crankcase, along with the wash down and carbon associated with cool running.

It was like the time some idiot decided he needed a generator. We have a wide variety of sizes from 3-100kW. They choose a 60kW with a JD engine similar in size to the 6BT to power 3 incandescent light bulbs and a phone charger. By the middle of the night it was wet stacking and coughing and puking.
 
#11 ·
s ǝoɾ said:
Keeping a diesel warm and loaded is very important.
Chrysler seriously considered the 4bt in early testing (Cummins in a Dodge tests started in '83) but politics and NVH prevailed. The 4bt is a very thrashy engine and a most people thought a 4 cyl engine meant no power.
 
#13 ·
uuhhhh.... deliver goods, bread, frito lay products, fed ex trucks, ups trucks, marine applications, generators, etc etc.

From Wikipedia
3.9L/4BT
The 3.9L/4BT Cummins is an engine in the same family as the 5.9 litres (360.0 cu in) Cummins turbodiesels. The 3.9L/4B is an inline four cylinder turbodiesel that was popular for many step van applications, including bread vans and other commercial vehicles. This engine is also used in various industrial, construction and agricultural applications. With a cylinder bore of 4.02 inches (102.1 mm) and a piston stroke of 4.72 inches (119.9 mm), the engine had a wet weight of 745 pounds (338 kg). In recent years it produced 130 horsepower (97 kW; 132 PS) and 355 foot-pounds force (481 N·m) of torque. The 4BT today is also popular as a conversion engine among many light-duty pickup trucks that were originally equipped with gasoline engines. This is due to its high fuel efficiency while producing power comparable to the original light-duty gasoline engine. The 4BT engines have the same pistons, connecting rods, valvetrain components, and injectors as their 6BT counterparts.



So the possibilities are endless. Look at cummins/onans website and you can find more. Or look at 4btswaps.com


Im trying to weigh the balance so to speak.
I want decent power, good mileage a broad power band and a dead nuts reliable engine that is strong and parts available anywhere. Oh an I want it lighter then my current engine (360) but will work with my existing drivetrain or at least a mopar component.

I am looking at a diesel to ditch the ignition system (distributor, plugs, wires) an get better mileage and wear and because I work on diesels most of the day they are intriguing me.

 
#15 ·
LOL.... So true Joe. Out of all the things coming through our motorpool 90 percent is body related, doors mostly. Then its suspension, AC components, electrical (voltage regs and alternators... 400 ampers are a killer), etc etc.

We have yet to pull or have to work on an engine. Only reset trouble codes or sometimes a transmission module will throw the engine into limp mode.

Ignore the 6.5 turbo diesel HMMWVs. The damn injector pumps are keeping me awake at night. It cant be a cold start solenoid but how the hell does a bottle of water fix the problem? Other then that the only diesel engine I have seen the pistons on since I been here is an old MEP02 5K generator that we did a headgasket on. Thats only due to the pushrods being damaged.
 
#16 ·
willy J said:
Ignore the 6.5 turbo diesel HMMWVs. The damn injector pumps are keeping me awake at night. It cant be a cold start solenoid but how the hell does a bottle of water fix the problem? Other then that the only diesel engine I have seen the pistons on since I been here is an old MEP02 5K generator that we did a headgasket on. Thats only due to the pushrods being damaged.
Easy, piece of cake.

The solenoid windings get hot and gain resistance, which reduces magnetic holding power. Cool down, increase holding power.

Depending on the operator/team (CAB unit) we either installed a 8" "electric injection pump fan" or instructed the drivers to "if it doesn't start, just turn your windshield washer on"

They were confused, but there is no mad science, just spliced a hose into the washer reservoir for a cool stream on the solenoid. ;)

There was some MWO for a altered IP timing, but setting timing is a PITA and involves a nonexistant timing light, that does exist, but no one has.

Every cummins problem starts with "which one is plugged? Your airfilter or your fuel filter?"
 
#17 ·
There is supposedly an improved solenoid. if we got them they are not working. most of the time we have the operators clean up their truck and do the best we can to get some kind of ventilation there. we replace them when we can. parts are getting a little scarce. Funny thing. it mostly happens on the  11551s not so much on the m998s. I think the turbo cooks them.
 
#18 ·
magnumRC said:
A 4bt is only 200lbs lighter than a 6bt and they cost about the same. Quite often the 6bt is cheaper because there are so many of them around.

The huge advantages of the 4bt are the length and the load factor. Cummins refused to offer Chrysler the standard 300k warranty on the 6bt because it is too much engine for the application. Cummins was concerned with fuel wash, carbon, and cylinder scoring issues because the 6bt in a pickup wouldn't be worked hard enough. The 4bt is the perfect size for a pickup. Since it has to work harder in a pickup, it is much more efficient than the 6bt.

Shy away from the 435. Find a 5-speed. If you decide to keep the 435 I would change the input shaft to at least an 1 1/4" 10 spline shaft. Clutches will be much easier to find it will be much stronger than the stock shaft. You might even think of installing an auxiliary transmission to get more gears.
What is the dressed and loaded weight of a:
318
360
440
4BT
6BT

I would like to keep the 435 and would rather beef it a little more if possible. Also I would look into the gear splitter option also. So for crawling and freeway the diesel sounds like good option. How bout sand, mud, snow? Reading another post it sounds like they are not the hottest for that?
 
#19 ·
willy J said:
How bout sand, mud, snow? Reading another post it sounds like they are not the hottest for that?
I'm sure you have used them in all of those conditions. How did they work for you? I've never had a winch line out to unstuck myself....
 
#20 ·
Big difference between the capabilities of an M931A2 or M998 as compared to what I will and can do it my W150.

I have always kinda felt that the RPM limitations on the military vehicles held it back in some instances. Also there is the amount of weight that keeps smart/experienced wheelers out of situations that you willingly put your own rig through.

I have run M998s through NV and never been stuck. We dont have that deep mud that Texas and Louisiana is fond of. When I was an 11M in GA I never got a M998 or M35 stuck in good ol GA clay. Some people did.... going where they should not have or not knowing to keep the flotation up. An believe it or not.... never drove a military vehicle off road in deep snow. So I have no basis for that experience. That and all military vehicles now a days are automatics. So I have no real experience with a light duty vehicle with a smaller lighter diesel mill coupled to a manual.

I guess im totally willing to experiment. So I might as well quit asking the theoretical questions and just go straight for the how to make, who makes what and how can I hook this up fabrication and assembly questions.

Still need those weights if anyone has one. Truck is heavy enough as is and as is planned. I dont want to keep adding more. So I really want to see the actual numbers between the listed engines as far as weight is concerned.
 
#21 ·
willy i have a 4bt in my 78 w200 i have a ford zf 5 speed the gears have the same kind of spread as the 4 speed but i have 4.10 gears so i need od.but as far as tranys go there are so many choices you wound int imagine go to 4bt swap and read some of the stickys lots of info
 
#22 ·
willy J said:
What is the dressed and loaded weight of a:
318
360
440
4BT
6BT

I would like to keep the 435 and would rather beef it a little more if possible. Also I would look into the gear splitter option also. So for crawling and freeway the diesel sounds like good option. How bout sand, mud, snow? Reading another post it sounds like they are not the hottest for that?
These are approximate dressed weights.

318: 525lbs (same weight as a slant 6)
360: 550lbs
440: 670lbs
426: 765lbs
4bt: 932lbs
6bt: 1120lbs

Mine is great in the sand- even with mud tires. I got stuck real good on a big chunk of driftwood and that's it. I could start and stop easily in the dunes.

I haven't driven mine at all in the snow.

In mud I run out of RPM real quick- it's only an issue with a manual transmission.
 
#23 ·
Geez thats a big jump in weight going from a 360 to a 4BT!!! Hey thanks a lot for getting those numbers! Appreciate that. The weight factor and the RPM limitations are making me second guess the install into a dedicated crawler truck to go to Moab or the Rubicon.

Hey JD. Got pics or a link? I have read the 4BTswaps! Pretty good info there. Just feeling around for more info.

How well would the 4BT work in a Ramcharger hooked to a 727/518 with 3.23s and 31 or 33s?
 
#25 ·
I did not. Thanks Jungle!


So far what I have learned.

1. A 4BT swap will perform better in my truck then a 440 or a fuel injected 360 will. It will get better mileage and will have more torque. The RPM range is a negligable issue that should not be a factor against the swap.
Q. What fuel options will I have with the diesel? Bio, Vegetable, etc etc? Ability to cross over back and forth?

2. It looks like everyone who does the 6BT swap only does so for conveniance and availability.

3. It will weigh more, but the weight penalty will be offset by the performance gain.

4. It will be expensive and time consuming. Mostly in either getting a donor truck or gathering and fabbing conversion parts as well as testing and tuning and farming out what I cant do.
Q. For what I want to do what is the best years of donor trucks to scrounge?

5. For all the effort it will take to get a 435 to bolt and work I may be better off finding a donor truck with a 4500. Do I still have the option to use my current NP 241 which is off a NP 435?

6. I can keep my 1/2 axles. I still my need to regear my 3.55s higher 3.23s or even 2.90 or try to go with taller tires. This makes no sense to me. Someone please help clarify. Im getting a little mixed up here.
 
#26 ·
The "expensive and time consuming" part is only true to various degrees depending on luck and skill, mostly luck.

I have seen a swap done in 2 days with less than a few hundred spent. On the other hand that was the crudest swap I had ever seen, and the luckiest. He just happen to have almost all of the needed parts just laying around and had the most bare bones dodge d series ever built.

Manual brakes and steering meant no problems there. He machined some plate to reuse his old 727. Did not do any wiring except 1 cable from alt to starter to battery, and a push button going to starter solenoid. Used angle iron motor mounts and an old 440 rad and I do believe the engine was a non turbo model from his dozer? probably the hardest thing he did was lift the clip/cab 3".

Of course, no one wants a build that shoddy, but I only point out there is a million ways to do it, and your own resourcefulness will dictate the time/money required.

Of course, for someone w/o an engine, that alone can be a significant cost.

Yes you can use your 4500 with 241. That combo came from the factory for many years behind 318, 360, 5.9 cummins, and 8.0v10.

The v8 models used common 23 spline just like yours do. As a matter of fact, the nv4500/241 combo came out around 92 and was available in w series trucks.
 
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