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1986 MJ build/ questions

P

podm98c

NAXJA Forum User
Location
napoleon,ohio
I know there are a few threads on this but here it goes. My 1986 mj has the 2.8l in it and i plan to swap it out.Now for the swap i plan to do a 3.4 swap but recently i came across a wrecked xj with 4.0. As far as my sanity goes should i just go with 3.4 or should i do 4.0 swap?


1986 Mj
Dana 30 (4.10 GR)
Dana 35 (4.10 GR)
2.8l ( no compression in number 4)
Ax-5
Np 207
 
i am not all knowing on GM V6 jeeps but i will tell you that you should get rid of that motor as quickly as possible. I dont know what kind of mounting issues youre going to run into as far as getting the 4.0 in there but you have got to get rid of the 2.8. I did a renix to HO swap on my jeep and all in all its not too difficult if youre something like a professional technician. Just dont be bashful. rip the truck down to metal and start from scratch. I wouldnt waiste any time doing a renix to renix swap either, if youre going to do the work, do it right. also a late model swap is a great thing as well.
 
Simplicity, 3.4 is basically a drop in.
4.0L will require "massaging" the bulkhead, and new wiring. I would definitely go for 4.0L VS GM motor.

Did you find an MJ or an XJ? Either way, hopefully HO. MJ wiring back from the cab is different from XJ.

Altho, why not go V8?
 
Mnkyboy said:
Keep in mind that a 4.0l is not going to fit your transmission so you will have to swap a new trans as well.
Your also gonna have to convert the front of the truck to accept the 4.0ls cooling system.

I would go with a 3.4l
Click to expand...
Would need a differnt t-case as well.
 
would a chevy 4.3 and 700r4 fit? i am wondering if the 2.8 and 4.3 engine families are close? as in motor mounts etc and size? me? i love the renix or the HO 4.0 they are sweet!
the 4.3 with manual would open up a granny gear first gear option . and the 4.3 is tried and proven engine. if with auto the 700r4 is kick ass too. can be made to do engine braking with modifications to drive off road like a stick. they can also be had with a low first gear as well.
 
4.3L will fit, but takes work.
GM 3.4L is a straight bolt in, of course with swapping intake and such. But is an "upgrade/replacement" for 2.8L
4.3L XJ did a 4.3L swap.
 
4.3l and 2.8l are completely different so nothing would be bolt in. A 4.3l is about the same work as swapping in a V8 since a 4.3l is basically a 350 that's missing two cylinders.

I have a 4.3l I'm getting ready to swap into my MJ but I am planning to adapt it to an AX15, its got a 700r4 hooked to it but I don't care for autos and I don't like the crappy gear ratios on the 700r4. I thought about using the NV3500 that would have come behind the 4.3l but the granny gear is no better then an AX15s first gear and the max torque rating from what I can tell is actually higher on the AX then the NV.
 
I am interested in how you are going to put a 90deg sbc pattern 4.3 onto an ax15. I looked into doing that for a friend and found no easy cheap ways to do it.
 
My wallet isn't fat enough for that :gag:

I keep forgetting how much novak/AA want for stuff. Low production numbers + custom engineering = expensive, I guess.
 
Wait....he has a wrecked XJ already. Put them side by side and swap everything.....should be easy and he'll have all the parts (transmission and all)

I'd go the 4.0 all day long over that gm v6.
 
Agreed, though depending on the year of the donor he might end up deeper into the wiring harness or other stuff than most people are comfortable with. What year is the wrecked 4.0 donor you found OP?
 
It all depends how much work he wants to do, the 3.4l is a decent engine and it can be swapped in a day. A 4.0l swap is gonna be a bit more involved, especially on an 86.

In my case the way I built my bumper and winch box a 4.0l won't fit in my truck so the 4.3l is a good option for me,power similar to a 4.0l but a much smaller package.
 
Mnkyboy said:
It all depends how much work he wants to do, the 3.4l is a decent engine and it can be swapped in a day. A 4.0l swap is gonna be a bit more involved, especially on an 86.

In my case the way I built my bumper and winch box a 4.0l won't fit in my truck so the 4.3l is a good option for me,power similar to a 4.0l but a much smaller package.
Click to expand...

You'd have to elaborate.....I can get a 4.0 out with just pulling the radiator....my hoist can pull it right out
 
20121230_105101.jpg

20121222_091158.jpg


Even if I moved the control box a 4.0l would hit the winch. When I built it I was planning a 5.3l swap so I wasn't worried about space but I had a 4.3l GMC Jimmy fall into my lap so I decided to go with the 4.3l instead.
 
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