2.8 to 4.0 swap

[Car RamRod]

I got scattered information from a search but I just wanted to doublecheck everything here.

 

I have an 86 MJ 4wd with the 2.8 and 3 speed auto which is just terrible with power and on gas. I can pick up an 88 or 89 MJ with the 4.0/5speed 4wd combo for 300 bucks. With the donor vehicle would this be a hard swap to do? I have no problem modifying the firewall but I think it's already set for the I6.

 

Thanks,

Matt

[Geonovast]

Wait...are there two donor vehicles?

 

 

Otherwise, why not just drive the one with everything in it?

[DirtyComanche]

For $300 the donor is probably screwed.

 

 

 

It should be an easy swap.

[Car RamRod]

sorry if I confused you, theres only one donor, I am just not sure if its an 88 or 89.

 

I'm not sure the condition of the truck as I am going to check it out and probably take it home on monday. But in any event my truck has like 73k on it and the body is perfect so I'd like to stick with that truck atleast. But we'll see.

 

As long as I'm not getting myself into too much work with this swap. Is there any computer related stuff for this swap, or any articles you guys know of that would help me out?

 

Thanks for the quick answers,

Matt

[Oizarod115]

you'll need the computer and stuff from the 4.0 yeah, the 2.8 will be carburetted iirc, but with a donor it shouldnt be hard

[DirtyComanche]

The wiring harness must be swapped in it's entirety. The rad support and rad must go. The motor mounts must change AFAIK.

 

 

And a bunch of other stuff.

[Car RamRod]

ooh ok, but as long as the donor runs I should be in pretty good shape and not have to rig anything right?

[Geonovast]

Just thought of something...from what I understand, since in 86 they didn't come with the 4.0, the firewall design was different, and you can't fit a 4.0 in there without pounding in the firewall. I know the 4.0 in my 88 XJ sat pretty close.

[JeepcoMJ]

as a swap, with a donor, it's not hard.

 

swap literally EVERYTHING from the donor. including the rad support etc. your hood will also have to be changed (be it altered or swapped entirely) to the 4.0 style, as the latches are different (one on each side)

 

the motor mounts bolt up to the frame, tranny to crossmember (but crossmember location will change to a different position...don't worry, the holes should be there)

 

depending on the earliness of your truck (early 86) it may need a bit of a pounding on a part of the firewall to clear the 4.0. a sledge will fix it easily and it won't affect anything behind the firewall. don't let anyone tell you you have ti swap firewalls, cause they are 100% wrong.

 

it shouldnt take long to swap, but will require you to drill out some spot welds on your rad. supports (sides, and lower) and weld them in on the 2.8. no big deal.

 

if it were me, I'd put in a 3800 buick motor from a camaro or firebird... :brows:

[Car RamRod]

thanks for the replies

 

I picked the donor the other day. All it needed was a battery and she fired right up on 3 year old gas. The trans shifted like butter as well, however the engine has some pretty serious blowby so it will need a rebuild, but I half expected that. I took her for a spin and this 240k mile engine feels like a beast compared to my 75k 2.8 anchor.

 

Everything that needs to come off the donor looks solid, and I am going to changing the interiors as well so when I pull the dash I'll mod the firewall as much as I need to and then just swap it all over.

 

I'm assuming it would be best to start with the engine bay of the 86 being completely bare and then going from there as nothing will interchange? I'm gonna be changing the dash, the cluster, pedals of course; pretty much everything. And I'm thinking the fuel system and tank will need to swap over as well?

 

But I'm still in planning stages; I'm probably not gonna start to work on it for another month or so.

 

Thanks,

Matt.

[90PioSport99]

thanks for the replies

 

I picked the donor the other day. All it needed was a battery and she fired right up on 3 year old gas. The trans shifted like butter as well, however the engine has some pretty serious blowby so it will need a rebuild, but I half expected that. I took her for a spin and this 240k mile engine feels like a beast compared to my 75k 2.8 anchor.

 

Everything that needs to come off the donor looks solid, and I am going to changing the interiors as well so when I pull the dash I'll mod the firewall as much as I need to and then just swap it all over.

 

I'm assuming it would be best to start with the engine bay of the 86 being completely bare and then going from there as nothing will interchange? I'm gonna be changing the dash, the cluster, pedals of course; pretty much everything. And I'm thinking the fuel system and tank will need to swap over as well?

 

But I'm still in planning stages; I'm probably not gonna start to work on it for another month or so.

 

Thanks,

Matt.

Matt,

I have heard on some occasions the later half of the 1986 model year was ready for the 4.0. I have never seen this with my own eyes but on XJs anyway, I have heard it to be true. At any rate as long as you're willing to redo the front supports, it shouldn't be too bad. Keep us posted on how you do. Good luck!

-Collin