4cyl, 2x4 to 6cyl, 4x4

Sorry! I know this has been asked and answered a few times already, but....

If I buy a 4 cyl, 2x4 MJ and I have a complete donor XJ for a 6 cyl, 4x4 swap into the MJ, will everyhing bolt right in or will I have to change engine mounts, etc.????

Thanks for the help!!

Thats one heck of a project. IDK particulars about mounts and things, but you will surely have to swap harnesses and maybe even go deeper to get things to work. I'm sure its able to be done though, just make sure you have the time for it and are committed to it all before you start.

If the 4-banger is 1987 or newer, it's a bolt-in swap, albeit an ambitious one. The '84 thru '86 XJs and '86 MJ engine compartment was different, the entire front clip around the radiator and the radiator supports was different, and it is widely reported that the firewall is also different.

If the MJ is '87 or newer, it's all set up to accept an in-line 6. But you have to swap everything including the complete engine room wiring harness. And if the XJ isn't the same generation as the 4-banger, you may have to swap the dashboard (gauges) and do some interior rewiring as well. (The '87 thru '90 were the AMC "Renix" injection system, from '91 on they used a Chrysler system. Even the polarity on the gauses (and sensors) changed in 1991.

Do you have to change the motor mount brackets? My son wants to swap his '88 to 4.0L.

If the 4-banger is 1987 or newer, it's a bolt-in swap, albeit an ambitious one. The '84 thru '86 XJs and '86 MJ engine compartment was different, the entire front clip around the radiator and the radiator supports was different, and it is widely reported that the firewall is also different.

 

If the MJ is '87 or newer, it's all set up to accept an in-line 6. But you have to swap everything including the complete engine room wiring harness. And if the XJ isn't the same generation as the 4-banger, you may have to swap the dashboard (gauges) and do some interior rewiring as well. (The '87 thru '90 were the AMC "Renix" injection system, from '91 on they used a Chrysler system. Even the polarity on the gauses (and sensors) changed in 1991.

i'm not trying to upset anyone but my 87 has adifferent rad mount from the 88,

is there a production date i can check to accuratly see what ive got?

i'm not trying to upset anyone but my 87 has adifferent rad mount from the 88,

is there a production date i can check to accuratly see what ive got?

Are you comparing an '87 6-cylinder to an '88 6-cylinder, or are you comparing one 4-cylinder to another 6-cylinder?

The 6-cylinder radiator is significantly wider than the 4-cylinder radiator, and the mounts are completely different.

I have done a similar swap your about to do and it is not that bad

I took a 1989 4cy 2wd 5sp Comanche and swapped in a 4.0, auto, 4wd system into it from a 1987 Comanche 4x4 that was rusted out (frame was shot)

Now you are using a XJ for the donor so I would think all the hard parts are the same but the wiring could be different?

First you need to pull all the items below from the donor 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 THE CAB (again this is on a Comanche) (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 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 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) Shifters for the auto floor if needed and transfer case shifter

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

You have to install the auto shifter and transfer case shifter ect..

Now there are other incidentals that will be obvious that is not on this list, 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 questions that are related to the swap and would be more than happy to do so

_________________

1989 Comanche 4.0 auto

Thanks for all the responses!!

I am currently trying to make a deal on an 88 MJ, 4cyl, 2x4 and a 91 XJ 4.0 4x4.

I should know more by this evening, but if everything works out I want to swap the XJ stuff into the MJ..... we'll see!!!

Then the questions will really begin!!!

Thanks!!!!!!!!!!!!!

Thanks for all the responses!!

 

I am currently trying to make a deal on an 88 MJ, 4cyl, 2x4 and a 91 XJ 4.0 4x4.

 

I should know more by this evening, but if everything works out I want to swap the XJ stuff into the MJ..... we'll see!!!

 

Then the questions will really begin!!!

 

Thanks!!!!!!!!!!!!!

A 91 XJ will be a high-output 4.0L, but you're already wanting to swap everything electrical I see.

You will need a custom driveshaft for the rear.

Possibly a different/cutom crossmember. I also assume that both are automatics?

I wonder if the transfer case linkage will need modified?

I wonder if the 4cyl fuel pump will pressurize a 6cyl?

You do know MJs are sprung under & XJs sprung over, correct?

(on this note, rear shocks/mounts are different between the 2)

That's all I can think of for now...

the x-member will be the same, and you should have the correct bolt holes in the unibody already, might need some nutserts to install in those holes, and you'll need a new trans mount.