4bt cummins into a CJ5, and some other questions...

I have a 77 CJ5 with the 304 and 3 speed manual, and i love my jeep, and the 304 runs good, but im a diesel nut, so i really want to put a 4bt cummins in my jeep, and the transmission sucks, so it was gonna have to go any way. I know that the axles and transfer case will have to be upgraded to, but would any body out there be interested in any or all of these parts? Any tips or pointers for this swap from anybody that has done one? Any reccomendations on the transmission, transfer case, or axles to use?  

Oh yeah, i wont be doing any rockcrawlin, rarely if any hardcore stuff, and its on 33s now and i might go to 35s later, but that would be 3 or 4 years from now. Not sure what axles would be good for this swap  

One of the only reasons that the 4bt might make sense would be for rock crawl'n.

A 4bt puts out 100hp and 250ft torque. Your 304 puts out 150hp and 250ft torque. The 304's power band is much broader and would be much more enjoyable to drive around than the 4bt.

A cam and intake manifold from Edelbrock will push your 304 over 200hp and 300ft torque. The 4bt would pale in comparison in any arena.

The front Dana 30 is fine for 35's if you're not hard core. But the rear Model 20 is a dog. A '72-'75 CJ rear Dana 44 will bolt right in.

The other problems that you're probably feeling is the lack of proper axle gearing. Proper axle gearing will go a long way for your driving enjoyment. For 33's you should have 4.10 axle gears. That alone may make you satisfied with both your engine and your tranny. The other downfall is the Dana 20 x-case.

The Dana 20 is plenty strong, it just doesn't have a low enough lo gear. A Dana 300 from the '80's CJ's has a much better lo gear and the front driveshaft output is on the same side as your CJ. The problem with swapping the x-case is expense. The x-case isn't that much but the adapter for the tranny or a tranny swap at the same time would be in order.

A lower lo gear would make you happy crawl'n. The right axle gears will make you happy all the time. And a new Edelbrock intake and cam will make you forget all about a 4bt swap. Unless it's just about a diesel and not about improving your performance both on and off-road.  

I just wanna say I love the idea of the cummins.  I love seeing a diesel tear through the mud, and what better than a cummins in a Jeep!  

High horsepower and high revs are what tear through mud. Like I said in the previous post. It might make sense for rock crawl'n, but for mud?  

Ive taken both my 99 and 05 doge 3500 duallys throug mud up to the frame. Both of them have 33/11.5 maxxis mud tires, and while yes there might be 6 tires, with my toolblox full and a full tank and the random crap in the back, both have wieghed in on the QT truck scales at a tad over 8,000 pounds. While high revs can be helpfulin the mud, as long as you can spin the tires fast enough to clean out the lugs you are fine, you cant really spin them faster and clean them more, if the lugs clean out at 2500 rpms, they arent gonna be cleaner at 5,000 rpms. If the gears were so low in the diesel that you couldnt spin the tires fast enough, then it would be a problem, i agree. Even with really low gears, like the granny gear in my six speed dodge, the torque off idle is low enough that i can start off in second or even third, and the tires will spin plenty fast enough. ftgiles, i wasnt trying to offend anybody on that other post, the whole post was my opinion, a little biased, i know, and the attitude was supposed to be sarcastic, its kind of hard to portray that thru the computer, lol. If i was trying to be an ass about it i wouldnt have called yall bozos, may be *** or something if i was trying to be a dick head, sorry. In most other countrys, you can get a diesel in almost anything, and in a lot of those countries there arent many paved roads, and they seem to do just fine. I know that with the right gears that my 304 would be adequate, but not only is the diesel a candidate for the better economy (my 05 dually averaged 14 MPG last weekend pulling a 30ft cow trailer in the mountains of kentucky, my jeep takes 2 gallons just to crank, lol), we have a farm so everything here is diesel powered. You can run a diesel up near the redline all day long and it will go anywhere and not break, it will use a lot more fuel, but if is neccessary, it can. Also if you throw a snorkel on a mechanically injected diesel, it is waterproof, or about as waterproof as an engine can get. There is no spark plugs, distributor to get wet, carb to screw up. You can still cause problems with vent hoses taking on water and water leaking in different places, but it has a better chance of surviving than a gas burner does. Also, being mechanically injected is a good thing. The 12 valve 6bt that is the big brother to the 4bt, is arguably the most reliable of all the modern cummins engines. They are easier to fix and work on, and even though you cant "chip" the computer, the fastest diesel dragsters and the most competitive sled pullers are all 12 valves. Some of the guys even yank the newer common rail and regular 24 valves out to replace them with 12 valves. If you are curious about the diesels performance just go to www.dieselpowermag.com and read some of the articles. Its old news to farmers but a lot of people are just now realizing the potential of diesels. All it take to make big power is add a lot of fuel and suck a lot of air. And again, i apologize if i pissed anyone off, i was kinda suprised when i realized i did, thats now what i was going for..  

I personally agree with a lot of what you've just said.  Diesels truly have a lot of potential, diesel was first used in the 80s I beleive(1985?).  Gas has been used for about a hundred years and I beleive everything we can find out about it has been found out.  Diesel already has proven its worth and definitely has more to be found out.  But really it's just an opinion is what matters.  I probably oughta shuttup before I end up calling it the wonder fuel and start an arguement.  But a diesel CJ5 would be unique and cool.  Especially with a cummins!  Can't wait to see more on this build.  

Well, you still cant talk me out of the diesel swap, but my checkbook has talked me out of my jeep. I havent sold it but it is for sale now. Hate to see it go, but ive got too many toys, not enough money, and seriously doubt that NObama is actually gonna CHANGE anything for the better, so id rather have the money instead of a jeep i cant really afford, cause being a farmhand doesnt pay very well.  

Save the jeep and put the 4BT in it.  Here is my son's starting a run through the mud.  With a few modifications, you can get it to run in the mud pretty well, and still have the torque for crawling.

 

I like the idea of a diesel Jeep. I tried to find one that would work in my Willys with no luck. The closest I came was a Kubota 100 hp diesel 4 cylinder. The problem is the weight.Aprox. 700 lbs. About the same as the 4BT.The best engine I could find would be a 5 cylinder Mercedes turbo. The problem with it is the length. It would fit nicely under the hood of a CJ5 or CJ7 but will not fit under the Willys hood.

I'm still looking for the best diesel,but have a Oddfire V6 sitting on the engine stand...  

If you are looking for a diesel for the Willys, find a VW diesel.  They are small enough and can be "Performance Enhanced" pretty easily.  

sweet jeep rrbgtt! what trans are you running


i'm going to drop a 4bt in my TJ someday, with a nv out of a dodge  
My Junk:
98 TJ
86 XJ
83 J20
61 CJ6