View Full Version : CJ diesel?

11-24-2006, 02:35 PM
I'm getting ready to start my dream project which is an '86 CJ7. I've decided to go diesel but I have very limited knowledge. I think a cummins 3.9 sounds good (mainly because I've seen it in a couple Jeeps already,) but I'm still not sure. I would like to go with a 6 cyl., because I would like to tow with it a little, and I do intend on some offroading. This will be my daily driver, and I drive 60 some miles a day. Either way, diesel seems to be the way to go but I obviously am having trouble choosing a motor and trans. Not to mention because my knowledge is so limited, I will need a shop to do the install for me, and I have no idea where to start looking for one. I live just outside Chicago. Thanks for any help or suggestions that you can offer up.

11-24-2006, 03:35 PM
First off, welcome to DTR.:)

2nd, please, please tell me I didn't see a "G" on the end of Cummins![nonono] That is a touchy thing around here![laugh]

As to your CJ project, I'll give ya my .02 since you are asking about two things I love - CJ's and CTD's......

CJ's have been in my family all of my life and we have had 4 CTD's.....the 6 cyl B series CTD really has no place in a CJ, at roughly 1100 lbs fully dressed and easily too long to fit in a stock engine compartment without cutting out the fire wall or extending the front clip, it simply won't fit and is far too heavy to be practical especially if offroad performance is a factor. Also, consider that a 1 ton driveline should be in place to reliably handle the level of torque it will produce.

The B series 4 banger is by far a better choice for a CJ. At roughly 700 lbs fully dressed and easily short enough to fit in the stock engine compartment, it just makes more sense. When turbocharged, they can make some respectable power but it won't be a rocket. We have seen 250 hp and nearly 700 ft/lbs of torque from these engines when properly equipped.

As for the transmission, if you want to have a reasonable axle ratio for general use and offroading, you WILL need an overdrive to use this engine effectively for highway use....it will simply be out of it's efficient operating rpm range if you don't. At this point, there is no auto with OD that will reliably handle the level of torque that is short enough for the 94" wheel base and will bolt to the engine. A standard is your best bet. This really narrows down your selection....I wouldn't consider anything else but an NV4500 for this application. There is tons of aftermarket support for it, it has many clutch options, you get a granny first gear for offroad and an OD for the highway, nearly any transfer case can be adapted to it (including the Dana 300 that would be in the 1986 CJ which I would retain since it is the single best transfer case offered in most any Jeep unless you are going to be making some big torque), it is small enough to fit without any hassles and isn't too heavy (OK, 190 lbs is heavy for a CJ tranny but when you consider the options in this category, it isn't so bad...an NV5600 weighs in at 340 lbs!:eek:).

That said, and considering I am a die hard diesel fan, there just isn't a diesel available yet that I would put in a CJ if performance is a priority. They are just too heavy and slow for a little sporty vehicle like a CJ. Sure, a heavily bombed 4 BTA can kick out 250 hp/700 ft/lbs but that isn't a stock engine that will do that....and you WILL have to run a 1 ton driveline to reliably handle that level of power. In this day and age 250 hp isn't that much for a vehicle that will end up weighing in at over 5000 lbs with that driveline.

It is very difficult to compete with a small block GM in a Jeep.....it is a very inexpensive and reliable way to get a lot of power and reasonable economy. Will it get the mileage of a 4 cyl Cummins? Of course not, but it won't perform like a 4 cyl Cummins or cost as much either.

To each his own.....it really depends on what your priorities are. If your priority is an efficient daily driver at the cost of other performance elements in which a CJ was originally intended for, then it would be an excellent choice....if hp, cost and offroad performance are important, find another engine.

Just my .02....:cool:

12-08-2006, 09:57 PM
Check out http://autos.groups.yahoo.com/group/cummins4BT/

02-11-2007, 11:41 PM
There are several B series powered CJs running around the Sacramento area.
The coolest is a CJ7 with a 12v B out of a wrecked Dodge p/u. He fabbed up a complete new frame and streched out the front clip 6". Dana60s front and rear. NP435 transmission. I think an NP205 t-case. This thing MOVES!!:o

There is also a CJ5 with a 4BT running around. He used a Case tractor as a donor for the engine and radiator. 4 spd tranny. Stock t-case (D20 or 300, not sure) This swap is not very clean. There are major clearence issues underneath the jeep. The whole drivetrain hangs down really far. He claims this was done for drive line angles. I think I would tuck the drivetrain up as much as possible for GC and lengthen the wheelbase to improve d/l angles.

Either way, I don't really like the B series swap into a Jeep. The B is a very tall engine for a jeep. Clearence issues are hell.
Weight is another thing. IMO, you lose one of the major benefits of a jeep with a B series engine - light weight. Even a 4BT is significantly heavier than any Jeep engine, especially when you include the heavy duty equipment that has to go with it. Heavier springs, frame, drivetrain, cooling system. All this extra weight kills off road performance.

I am a die hard diesel fan. Its what I do for a living. I have researched the diesel jeep issue heavily. I really thought about a 4BT in my 90 YJ. But it just does not work out. I am going with a Ford 5.0HO when I swap out the engine. Light weight, good low end torque, great power, smaller overall package than a small block Chevy.

02-12-2007, 12:43 AM
Times are a changin'...wasn't long ago most rock buggies had small-blocks or even some decent big inch motors in them. Now its pretty moch all eco-tec, toyo, or honda engines powering the things, all because of weight. The diesel would be nice, but one of the greatest CJ motors ever was the Olds/Buick 225 V-6, great off-road, even if their wiring was a hack job. They didn't last real long, but the only diesel that could be decent in a jeep is a CRD Liberty motor, somewhat torquey, decent horsepower, nice power to weight. It probably isn't what you wanted to hear, but for a trail truck, your center of gravity, and weight are gonna be a big issue, a B series motor is tall, heavy, and slow...hope your not running any steep side hills, mud, or high clearance trails... Get what I'm saying?

02-17-2007, 09:22 AM
I have seen some VM Motori diesels for sale on e-bay. This is the same motor that is in the Liberty. Without all the emmission junk it should work pretty good in a CJ. I may put one in my CJ 5 when I can afford it.

02-18-2007, 01:09 AM
I know the guys at the local Detroit Diesel Dealership. They work on VM Motori stuff all the time. They absolutely hate it. Every engine in the VM Motori line up is junk.

Nate Frame
02-18-2007, 11:44 AM
How about a Mercades diesel out of a sprinter, or a VW TDI engine that has been ''suped up'' a little? Look at the cummins B 3.3, there is a thread that is about 7 pages long on this forum. E-mail they guy, says he is really happy with the engine.