4bt diesel in an xj - JeepForum.com

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post #1 of 7 Old 01-12-2011, 07:39 AM Thread Starter
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1998 ZJ 
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4bt diesel in an xj

i am currently going to school to be a diesel tech and i was thinking i would like to drop a 4bt into my jeep. the ratings for this motor is 150hp with 350 ftlb of torque. i was thinking i might have to upgrade the axels and t-case. i was wondering if anyone had any educated opinions, or comments on this swap. P.s. this motor is a 3.9 and not much different in size then the 4.0L six thats in there

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post #2 of 7 Old 01-12-2011, 08:24 AM
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I have seen it done more in wranglers than in cherokees. but I plan on doing this eventually as well but really havent looked into it much yet. I have seen people use an NV4500 for a trans but I dont remember what t case they used. My only concern is length and needing different driveshafts. You will also need to make new motor mounts and strengthen the frame a lot. That motor weighs more than a 4.0 so stiffer coils will need to be used too. As for axles, I would run something like a Ford 8.8 out back and im not sure how a Dana30 would hold up to the power. It would definitely need to be strengthened and not run with bigger sized tires.

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post #3 of 7 Old 01-12-2011, 08:24 AM
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I know its been done... I've seen it on the internet :-)

Google for 4BT Cherokee and I bet you get some hits. There's also a 4BT forum with pages on transmission options.


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post #4 of 7 Old 01-12-2011, 08:42 AM
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Do that in NY and the treehuggers will string you from a tree with your thumbs ... if you are lucky. I wish we could do diesel stuff up here

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post #5 of 7 Old 01-12-2011, 08:54 AM
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I am planning on beginning a diesel XJ project within the next 2 months, and am currently getting finances in order to do so. My dilemma has been my need for a DD with very good MPGs. My finished product will be a 1999-2001 XJ, preferrably 4 door, but a 2 door will do. It will be 2WD preferrably a manual, but still researching tranny options. Looking at the Cummins 4BT and the CRD engines. Will fully swap in a WJ leather interior, with full sound system. 2" OME lift with 29" or 30" Dueler Revo AT's on Moab rims. This will not see any dirt at all most likely, as I will be keeping my 4.0L XJ for my trail vehicle.

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"I pitty the fool who lists D30's and 31's, then tries to talk **** on PBB":

Originally Posted by Durt_Diver:
Those pics might be a little too flexy for this thread. You don't happen to have any pics of your friends xj on a curb by chance?
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post #6 of 7 Old 01-12-2011, 08:59 AM
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Originally Posted by thcmyth View Post
i am currently going to school to be a diesel tech and i was thinking i would like to drop a 4bt into my jeep. the ratings for this motor is 150hp with 350 ftlb of torque. i was thinking i might have to upgrade the axels and t-case. i was wondering if anyone had any educated opinions, or comments on this swap. P.s. this motor is a 3.9 and not much different in size then the 4.0L six thats in there
It is absolutely not a good idea to put such a big, heavy, tall, and low-powered lump in a small and light vehicle like an XJ. 4bt is in no way similar in size to the Jeep 4.0 liter engine. 4bt is taller, it's oil pan does not fit too easily with the XJ front axle, it weighs a LOT more than XJ engine, etc. It is doable, and I've seen write-ups and pictures of 4bt swaps on XJs, but IMO you have much better options available. One thing to consider is also the cost of the conversion; will you ever get your money back from the better MPG you get? If you're after torque, just stroke your I6 or do a 350 SBC swap.

4bt is a great engine, but it's not a good idea for the XJ. You would need substantial strengthening of the unibody; you'd need to plate the whole front of the uniframe both outer and inner plating + top and bottom - and it'd be a good idea to use frame stiffeners on the uniframe rails as well. What tranny would you use? What transfer case? Which axles? You can check from Pirate what kind of plating we're talking about from the guys installing 1-tons and 40s.

I've cvompletely rebuilt my XJ front end for the 1-tons + 39.5s, it's doable but requires a lot of work. Considering if you only want the great mileage and torque of diesel engines, it is a LOT of work for the gains you get.

I would recommend diesel engines from the early- to mid 80s Diesel Mercs, they can be built to substantial hp/ torque output, they are very durable engines (one of the strongest/ longest lasting passenger car engines built to date), and the size and weight is much more suitable for XJs than the 4bt. I don't know how easily you can find those engines in the Staes, but I would imagine some do exist. I've seen a build thread in Pirate where someone was doing just that, installing a Merc diesel to an XJ. One other option would be Datsun/Nissan SD33, add a turbo and be done with it. Slightly heavier than XJ I6, but lenght and height is pretty close to same. Not a high HP engine, but huge amounts of torque.

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1990 XJ Limited (4-door), 4.0 I6, AW4, NP242, ***rolled and totalled @ 165k miles***

***Under construction***
1990 XJ (4-door), 4.0 I6, AW4, NP242, PBR 42" tires, Unimog 404 portal axles, 110" WB, full cage + uniframe completely rebuilt, front 3-link + panhard / double triangulated 4-link rear,... ***SOLD***
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post #7 of 7 Old 07-14-2011, 10:33 PM
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2004 LJ Wrangler 
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This is kinda a bump, But within the next year I will most likely be puting a 4bt in my jeep. With:

NV4500 tranny
Dana 300 or similar Transfer case
Sterling 10.25 rear
Dana 60 front
4:10 gearing
37 inch Humvee tires/Humvee wheels
Frame stiffeners
Probably Exo cage.

I'm excited

Not all those who wander are lost - J.R.R. Tolkien

My LJ Cummins 4BT with 1 Ton's Build: http://www.jeepforum.com/forum/f9/20...ation-2703513/
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diesel swap , help please

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