hey guys im new to this site and ive been a huge fan of diesel power, in particulare the dodge side of the ring but any way, i have a 74 cj5 that im looking at swapping a 4bt into. First is the easy part i have already swapped out the axles and suspension to handle it (wide track axles, scout II front springs) my frame is boxed so i know itll handle it. the motor is actually a few inches shorter from the fan to the flywheel than the original 3.8L I6 so i know it will fit nice and easy. now the fun part, my goal is to kob one out of a bread truck with the TH-400 behind it and use a novak adapter plate to mate it to my tremec t150 i swapped in with the 5.0 i built last year. i know the trasnfercase will handle it cuz its a dana 20. But heres the million dollar question... Will my medium duty 3 speed hold up to the low end grunt the cummins makes? I don't think it will be too much for it as the motor in it now makes around the same torque as the 4bt but its at a much higher rpm, that is the only thing that makes me leary of the tranny holding up. the idea behind retaining my 3 speed is because i really only have about 84 inches of wheel base to dink around with so a nice compact drivetrain is an abseloute must to keep a some what decent rear drive shaft angle... btw its already lifted about 7" so depth clearance issues wont be a factor.
the whole idea behind this is so i can get better than my current 10 mpg and still maintain my nice torqey wheeler oh and be able to have a nice 5" stack come out right behind the passenger front fender that bellows nice large black clouds of wholesome diesel goodness!!!

Any advice at all would be a major, help thanx in advance

 

check out 4btswaps.com. Really good info and guys over there! They will be able to tell you if it is good or not.

 

yeah i just looked around there for a while and they don't really tell me anything about my tranny holding up to the 4bt i hope it will and if it doesnt then i guess i need to find a new solution

 

If the engine is shorter overall that what it's replacing, why not move the engine forward that distance (or more, if space provides) and use a t18/19? I think the 4bt would really punish the 3speed...the power pulses coming off the crank at low rpms have got to be pretty serious. Either way, good luck with the project--sounds like it's gonna be sweet when you're all done!

greg

 

well i supose that could work but i want room for a smallish intercooler so that really isnt the way i was heading, but i did talk to the pastor at my church he used to drag race pretty competatively and he had a guy that did all of his tranny work for him and gauranteed that if he dropped his tranny from first to reverse at 50mph he wouldnt brake anything at all so i might get his number and see what he thinks... i was also wondering if heat treating or chryo treating my tranny guts would help at all i would think it would do something either way yeah this thing should be quite the beast when done any way thanks for the post.

 

for starters, the dana 20 transfercase sucks. get something beefier. you'll thank me later.

second, go on pirate. in the hardcore jeep section, there is a guy swapping a 4bt into a TJ. check it out.

 

first off i know lots of guys running 20's and they havent failed yet the only problem i have is the not so low, low range but that can be remedied at any rate it says your in houghton, where?? MTU?

 

The 20 case is fine unless you feel like stepping up to a dana 300. a 20 is cheap and plentiful. Like you said, the only drawback is the low range. the t150 will hold the power of the diesel but you are limiting yourself on gearing options. I'd do the t18/19 swap with the short input shaft- that is realtivly close in length to your current setup. I ran a t150 behind a buick 430 that made over 510 ft/lbs on the dyno and it held up fine but I went to the t18. With that ultra low 1st gear you'll be able to go ANYWHERE. Just use the BIGGEST clutch you can get your hands on.

 

Why not check step van specs. The P30 is only rated at 1 ton. Fedex, Frito-Lay etc. run the 4BT. You only need at least what they use. I have a Fedex terminal near me and I hear manual trannies behind them. If you don't want the individual tranny, that Fedex uses, you need only determine what is comparable from another manufacturer. I believe the 4BT has an SAE #2 flywheel housing. If not it would be a #3 but I doubt it. The P30 step van is a Chevy product. Clearly, they have a means by which to join the engine to a Chevy trans. Also, the various applications have flexplates and flywheels. If you parallel their drivetrains the components will be out there for you.

I have driven T19's behind a Perkins 6-354, CAT 1140, 1160 and even a 3208. I currently have a T19 behind a 460. It has held up just fine. The 4BT is not a torque monster when compared to some other engines. The T19 was used in everthing from forklifts to bobtail trucks to school buses. It can handle the 4BT.