Engine Swap(2.5 to 4.0)

I searched but couldn't find anything of a 2.5 to 4.0. How much work would be involved? What would be needed?
-Engine and tranny
-T-Case?
-Wiring Harness
-ECU
-Radiator and cooling fans

What else am I forgeting? Thanks.

i have no practical knowledge about this but there have been several, if not many, threads on this subject during the past couple of years. Not sure what you will have to plug into search to find them -- "firewall" comes to mind.

I've done it. What year do you have?

In general, it is a big swap job. You need a complete donor vehicle to get the engine, mounts, radiator, tranny, wiring harness, and computer. If it is a pre 87, you need a hood, front radiator supports, sheetmetal to hold headlights (has to be cut off and moved).

On the early model XJ's, you have to cut off the vertical sheetmetal behind the headlights and move it to the new vehicle. It takes a touch of skill. You also have to "adjust" the firewall about a half inch in one spot with a BFH.

Unless you are a glutton for punishment, I recommend finding a nice 4.0L and buying it, then selling your old rig. In most cases it will be cheaper and a hell of a lot easier.

I have done the swap listed below last year and it is not that bad
NOTE: THIS IS A COMANCHE “MJ” SWAP SO THE XJ MAY HAVE OTHER REQUIREMENTS THAT I WOULD NOT KNOW
I would think most of the hard parts are exactly the same but wiring requirements may be different on the XJ
Thought this info would help you understand what is entailed in a swap

(THIS INFO IS BASED ON USING COMANCHE PARTS 87-89)

I took a 4cy 2wd 5sp Comanche(89) and swapped in a 4.0, auto, 4wd system into it from an 1987
First you need to pull all the items below from the DONER 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, NOTHING FROM INSIDE THE CAB (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 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. (4cy frame horns will not work with 6cy)
also get new engine mounts
3) You will need the 4.0 radiator (the front of the 87 AND UP (COMANCHE) 4cy truck IS 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?) again this is what i had to do on the MJ
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 4CY 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
7) axels frnt & rear if needed in your setup


Things like the cross member are the same also think about, 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 (87-89 FOR SURE)
And other things

Now I could have forgot to list some stuff but this is the “must have” parts I had to use
If you have some experience in engine swaps you will find this is not so chalanging I was able to do the complete swap in a week-end with 2 helpers

1989 Comanche 4.0 auto

Well my xj is a '93 so alot of things will be different I am assuming from the info of earlier swaps mentioned before. I would sell my jeep but the motor is not in it. I am rebuilding my 2.5 and I keep running into problems. So I was just wondering if it would be easier to do a 4.0 swap. Im considering just junking my jeep and finding another one.