1989 4.0 ENGINE SWAP

[JEEPNJR]

I currently have a 2.5l in my 1988 mj, and i am looking into putting a 4.o motor in it from my buddies wrecked 89 mj. I have restored my 88 my back better than perfect. But now at 200k on the motor its giving me all kinds of problems. How hard will it be to swap motors and is this a good choice for a swap. Will everything swap over easy enough? Has anyone done this type of conversion? I will transfer over entire engine, computer, trans, and the dana 44 rear from my buds MJ.

 

Thanks

:shock:

[pingpong]

I have never done this, but I have been told, everything has to be swapped, wiring, whole drivetrain, Drive shafts, computers, basically everything except the sheetmetal.

 

 

 

Patrick

[ComancheKid45]

I Swaped an old 4.0 for a brand new 1....but thats alot easyer i guess since its the same Engine 8)

[Bounty Hunter]

You'll have to check for clearance issues at the radiator and at the firewall, the 2.5L engine bay may not be long enough for the 4.0L.

 

Worse case scenario is you'll have to swap out the entire radiator support assembly for the 4.0L setup.

[DirtyComanche]

You need the rad and and rad support from a 4.0 version. And a bunch of other crap from the front area. You'll basically need a decent donor vehicle. Where's your bud's MJ wrecked?

[comanchedude]

Well

 

Your in luck I have done that exact swap your about to do and it is not that bad

And it is without a doubt the best upgade path

I took a 4cy 2wd 5sp Comanche and swapped in a 4.0, auto, 4wd system into it

First you need to pull all the items below from the 89 truck with the 4.0

 

1) Wire harness from “under the hood “that entails taking the complete harness from the front side of the firewall that’s it NOTING FROM INSIDE THECAB (except if auto tranny you will need the tranny computer but that will be part of the harness under the hood anyway) the wire harness basically bolts to the big connector on the driver side and wraps around the front of the truck around to the passenger fender and back to the center of the fire wall

2) After you remove the 4.0 engine with the tranny and transfer case “if 4x4’ you also need the engine mounts and (very important) you must also take the frame horns, that is the brackets bolted to the frame the engine mounts bold to.

3) You will need the 4.0 radiator (the front of the 88 4cy truck will be the same but you need to remove the spacer they bolt in for the 4cy radiator) it just unbolts

4) You need the 4.0 fuel pump (and tank if your 4cy was a carbureted version)

5) You will need to cut the 4.0 fuel supply hoses just before they mate to the steel lines at the frame of the truck, you need to splice these onto the 88 truck as the 4cy hoses have different ends and are to short

6) You will need to use the 4.0 rear drive shaft as well

 

Things like the cross member are the same also think about stuff like do you have tilt wheel if not, does the 4.0 truck if so swap that also. You can swap a standard gauge cluster with one with gauges on these years just by swapping the cluster

And other things

 

Now I could have forgot to list something but this is the “must have” parts

If you have some experience in engine swaps you will find this is not a big deal and I was able to do the complete swap in a week end with 2 helpers

If you have any questions just send me email I can guide you through any part of the swap

Now if you are not going to use the 4.0 driveline (tranny back) then you may need to work that part out as I used the driveline that came with the 4.0

Again I can help answer any questions that are related to the swap and would be more than happy to do so

[HatchetMJ]

I am currently doing this swap....its taking me longer than expected due to money issues and very limited times to work on it. What I started with was an 89 MJ 2.5L 2wd and bought a XJ with a 4.0L auto, and np242. You'll need all the stuff Comanchedude listed above to complete the swap. I also decided to swap out the dash in my truck witht he one from the XJ. I was switching from a manual to an auto though and have a console I want to put in that matches the dash so that is why I'm going thru the extra step. Make sure you change the motor mounts. That will solve your fitment issues. Also as stated above the radiator support that is in there for the 2.5L comes out with either 2 or 4 bolts and then is correct for the 4.0L radiator.

 

Good luck....hopefully mine will be complete this weekend....well minus a rear driveshaft...but that is only because it was originally 2wd

[JEEPNJR]

THANKS FOR THE INFO, VERY HELPFUL, MY BUDDIES COMANCHE WAS HIT ON THE PASSNGR SIDE, ALSO HIS MJ CAME WITH THE TOWING PKG, HEAVY DUTY RADIATOR, TRANS COOLER, AND DANA 44. I WILL BE USING ALL THOSE PARTS. :-D