2.8 to 4.0 swap quesitions

[redwolf624]

alright guys, i keep gettin harassed by my local jeep groups when i'm gonna drop a 4.0 into my MJ, i've heard i can without cuttin the firewall but i've also heard i can't without cuttin the firewall. now i do know i will need a new trans, reposition the motor mounts and get the wiring and computer but what else would i need if i was to do this, would i have to cut the firewall any, just wanna get some questions out of the way, it'll be a way later project but it is a dream of mine to have my MJ have a 4,0,

 

Redwolf

[onlyinajeep726]

Most of these questions can be answered by going through my build thread: http://www.cherokeeforum.com/f46/86-comanche-dd-159524/index4/#post2542580 (I went from a 2.5, though.) 

 

I did not have to cut my firewall, but I did smash it in with a BFH.

 

Since you're going from the 2.8, you'll have to source a 4.0L MJ specific fuel sender assembly and buy the appropriate pump.

Also, if you're using an XJ as a donor, a dash wiring harness will need to be adapted to make the fuel pump, fuel gauge, and tail lights work.  Here's the write up on that: http://comancheclub.com/topic/18588-xj-dash-harness-to-rear-mj-harness-wiring-guides/

 

Here's some additional links that may aid in your search: http://comancheclub.com/topic/39539-links-for-25l-to-40l-swap/
 

[Pete M]

essentially you will need EVERYTHING.  gut your truck down to an empty shell and swap it all over from a donor.  from driveshafts to fuel pump to dash wiring to exhaust.  you get to keep your axles and um... seats...  and doors... ummmm..... and headlights...

 

a 3.4L will go in with MUCH less effort.  you can keep your trans, your exhaust, you front shell, etc.  and you can even swap in fuel injection from the donor camaro pretty easily (it's a stand-alone harness unlike our spaghetti mess)

[JeepcoMJ]

Motor mount bolts for the frame side are already there...

[redwolf624]

essentially you will need EVERYTHING.  gut your truck down to an empty shell and swap it all over from a donor.  from driveshafts to fuel pump to dash wiring to exhaust.  you get to keep your axles and um... seats...  and doors... ummmm..... and headlights...

 

a 3.4L will go in with MUCH less effort.  you can keep your trans, your exhaust, you front shell, etc.  and you can even swap in fuel injection from the donor camaro pretty easily (it's a stand-alone harness unlike our spaghetti mess)

pete i figured that much, my main issue is that firewall and wiring, how bout the dash gauges? it's been a dream of mine to drop a 4.0 in my MJ since i got it,

 

Redwolf

[Pete M]

the easiest is to yank out EVERYTHING and swap over EVERYTHING from the donor MJ/XJ.  there is no reason to keep ANYTHING from your truck and then try to splice into it (except maybe the rear harness depending on what the donor rig is). 

 

as to the firewall, a big hammer should take care if it if you don't have a late year truck that already has the bump-out in it.  we're only talking about a small bit that's in the way.

[onlyinajeep726]

The fun part will be modifying if for the 4.0 radiator...  I had fun with that one.  Hope you know how to weld, are wiling to learn if not, or know someone who can.  Fabrication skills are a must.  I spent a good chunk of time getting the radiator support set up, and all that went with it like the hood latches, top support plate anchors, etc.  Hell, if you want an '86 with a 4.0L in it, you can buy mine lol.  It's pretty much turn key, all it needs is a little finishing touches to the interior.

[shelbyluvv]

Sell the 86 and buy a 87+ truck. You do not have the skill to pull off a 4.0 swap. We have been down this road with you, taking a few different routes, and we keep coming back to the same starting point.

[HOrnbrod]

^^  This. Dreamin, wishin, and yackin don't git er done.  :popcorn:

[Minuit]

A million times what the above guys said.

[redwolf624]

yeah i'm startin to see why everyone has told me to just get a 87-92 MJ, thanks guys, i think i know everything i need to if i were to do it,

 

Redwolf

[Kano808]

The fun part will be modifying if for the 4.0 radiator... I had fun with that one. Hope you know how to weld, are wiling to learn if not, or know someone who can. Fabrication skills are a must. I spent a good chunk of time getting the radiator support set up, and all that went with it like the hood latches, top support plate anchors, etc. Hell, if you want an '86 with a 4.0L in it, you can buy mine lol. It's pretty much turn key, all it needs is a little finishing touches to the interior.

Stopped me dead in my tracks when looking at swapping possibilities haha I am not about that crazy metal fab life haha

[JeepcoMJ]

Spot weld bit, cut the front I ner fenders out with it, and front crossmember. Real problem solver.

[onlyinajeep726]

Spot weld bit, cut the front I ner fenders out with it, and front crossmember. Real problem solver.

 

I thought about doing it that way and that suggestion was made after I looked into it, but I went for the more unique approach lol.  If you didn't know any better, it's almost impossible to tell a difference between it and '87+ models.  I ought to take some pictures of how it turned out now that everything is finished.