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Cummins 4BT YJ Build!

89K views 71 replies 32 participants last post by  Chris.400 
#1 ·
Hey guys, I know there is always talk and controversy over the 4BT YJ engine swap, so I figured I would post my build up here.

The basics:

This was for my senior project to graduate with my BS in Mechanical Engineering Technology from Penn State.

I started with an 89 YJ I bought with no driveline, almost new interior, but ugly faded canary yellow paint.

I drove to Ohio and bought a 4BTA that was in a bread truck, It came with the alternator, power steering pump, turbo, aftercooler and some other junk.

I bought an NV 4500 5 spd, adapter, clutch, flywheel, master/slave, bellhousing, from a dodge ram 2500 that had a 12v cummins.

I got an adapter kit to mate the jeep NP 231 to the NV 4500

Got to work....

These are pics right after I loaded everything up from my house to take down to the school shop. I built this Jeep in the Penn State Harrisburg campus Engineering shop.
 

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#2 ·
With the driveline already removed, I bolted the engine and trans together and lowered it in to start designing some engine mounts.

And yes, the NV4500 is 2wd in this Pic, I converted it to 4wd and adapted it to the NP 231. Pics on that will come.
 

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#3 ·
Then I had a minor setback..... this is why welding safety is so important. I learned my lesson, never walk away from something you were just welding on.
 

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#5 ·
These pics are mostly rebuilding the trans and assembling the driveline, i am missing a few of setting up the clutch and mounting the T-case unfortunatley.
 

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#6 ·
More of the trans, wish I could find the rest of the pictures. O well, I basically had to replace the main shaft, bolt on the new adapter, and the T-cas bolted right on.

The NV 4500 is super easy to pull apart and re-build with instructions. I bought a total re-build manual.
 

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#7 ·
So with the body of my Jeep torched, luckily I got a deal on a sahara body, it was a bit of an uneasy 3 hour drive back though....
 

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#8 ·
With the new body on the Jeep and the shop fixed, I had all of 6 weeks to get this thing running!!

I mocked up some foam motor mounts til I was happy with the design

Then I just started mounting everything. I am sooooo glad I found this intercooler, it fits perfect
 

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#9 ·
I got the motor mounts laser cut and bent, then welded them myself.

Then just some paint and I bolted them on
 

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#10 ·
Then fininished welding them to the frame, with a fire extinguisher in hand this time.:thumb:
 

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#11 ·
I will get more pics up tomorrow, but I just have to put the finished one up and a start up video.
 

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#17 ·
I have a thread on JeepForum.com as well, I dug up these pictures and figured I would make a new thread on here as well.

I hear so much controversy and assumptions over this swap that it drives me crazy.

Bottom line, it fits, its not too heavy, its not too loud, and its way more fun then the 4 other V8 Jeeps I have built and drove, but that might be cus I love hearing a turbo psssst every time I shift haha. :punk:

Low end torque is amazing, and fuel economy is great.

The swap is also quite a bit more expensive than a V8 swap though.

Also, I am selling the motor mounts I designed, PM me if interested.
 
#16 ·
This is an excellent build. Just be thankful only the Jeep body got torched. I've seen garages go up quick with similar situations.

I'm very jealous of your cummins.

Denis
 
#21 ·
Placement of my trans (before it caught on fire)

Sorry I am trying to put these pictures in some sort of order
 

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#25 ·
I really wish I had it driving right now, all these pics are from about a year ago when I was living in PA. Since I only had 6 weeks to build it, I cut a lot of corners, but I drove it to Virginia Beach, and tore it all back apart haha, i just got it started again for the first time in a few months last sunday, Soooo I am getting to those pictures.... if this internet would work:banghead:
 
#26 ·
Is the Jeep finished and on the road?
Would love to see more pics!
 
#27 ·
It was, I drove it a total of about 500 miles, but, I hated my rigged wiring, and I decided to install an XJ HVAC system in it, so I tore it all apart to re-do everything

I am in the process of completely modifiying a wiring harness from a FI 95 YJ to work how I want it, and also adding dual power distribution centers to have all the fuses/relays I could ever want to run accessories, and designing a new sheetmetal dashboard......So it is not on the road right now.
 
#28 ·
youngjeeper11 said:
It was, I drove it a total of about 500 miles, but, I hated my rigged wiring, and I decided to install an XJ HVAC system in it, so I tore it all apart to re-do everything

I am in the process of completely modifiying a wiring harness from a FI 95 YJ to work how I want it, and also adding dual power distribution centers to have all the fuses/relays I could ever want to run accessories, and designing a new sheetmetal dashboard......So it is not on the road right now.
Defiantly post some cad of the dashboard. I loved the custom motor mounts!
 
#30 ·
No prob, these were rendered a while ago when it was still conceptual, but you get the idea
 

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#32 ·
Ok, I think I got this thing working now....


Here are some pics of my intake/intercooler piping

For the piping I just bought a box of random exhuast pipe "test" bends off of ebay and pieced it together.
 

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