94 YJ Engine Swap

G-Bear

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I have a 1994 YJ 4-banger stick-shift that is so under-powered especially with the 33's and all the aftermarket bumpers, winch and other b.s. it's pushing. I want to take a cadaver vehicle such as a 4.0 and use the wiring harness and engine. Does anyone know if I can still use the stock tranny, transfer case and axles or do I have to replace all of that too?
 
G-Bear said:
I have a 1994 YJ 4-banger stick-shift that is so under-powered especially with the 33's and all the aftermarket bumpers, winch and other b.s. it's pushing. I want to take a cadaver vehicle such as a 4.0 and use the wiring harness and engine. Does anyone know if I can still use the stock tranny, transfer case and axles or do I have to replace all of that too?
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You could swap motor and harness, probably leave the transmission should be able to keep transfer case and axles. But me thinks you should try this since it seems like you don’t have a solid grasp on what all is involved. Maybe look into re gearing your axles since they probably are still stock


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The 4 banger needs 4:88 gears with 33s to equal the stock gearing. It will still leave you desiring a bit more.

The 4.0 swap is doable but you have to swap everything. Wiring harness, motor mounts on the frame will have to be cut and new ones welded on, trans, transfer case, cross memeber, all of it. The trans and transfer case are different for a 2.5, they have different output shafts. The transfer case is 21 spline and the 4.0 transfer case is 23 spline. They do make an adapter. The 5 speed tranny behind the 2.5 (AX5) won’t hold up too long behind a 4.0

It is very doable, but you need to have a whole donar vehicle basically, and it’s so much work, you could consider any other motor and have the same amount of work.
With that said, the 4.0 is a good swap it’s just that it’s a good time to consider what you want in the long run due to the fact that you basically have to ditch all the stock stuff and swap everything in.

If I did not care for a V8 swap and big power, and I could pick up a running 4.0 powered XJ/TJ/ZJ for real cheap, I’d consider it.
 
77GreenMachine said:
The 4 banger needs 4:88 gears with 33s to equal the stock gearing. It will still leave you desiring a bit more.

The 4.0 swap is doable but you have to swap everything. Wiring harness, motor mounts on the frame will have to be cut and new ones welded on, trans, transfer case, cross memeber, all of it. The trans and transfer case are different for a 2.5, they have different output shafts. The transfer case is 21 spline and the 4.0 transfer case is 23 spline. They do make an adapter. The 5 speed tranny behind the 2.5 (AX5) won’t hold up too long behind a 4.0

It is very doable, but you need to have a whole donar vehicle basically, and it’s so much work, you could consider any other motor and have the same amount of work.
With that said, the 4.0 is a good swap it’s just that it’s a good time to consider what you want in the long run due to the fact that you basically have to ditch all the stock stuff and swap everything in.

If I did not care for a V8 swap and big power, and I could pick up a running 4.0 powered XJ/TJ/ZJ for real cheap, I’d consider it.
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Basically everything he said.

What I'll add is that I had a 95 Wrangler 15 years ago with the 4-popper and 33s, and it couldn't get out of it's own miserable way when trying to do anything other than cruise speeds equivalent to the limit of active school zones. I considered doing the same thing - swapping a 4.0L, then started adding up the cost/benefit of having to source a new (to me) engine, harness, transmission, transfer case, etc. etc. I quickly found that I could build a relatively cheap SBC 350, so I went to the junkyard and bought a complete motor and TH350 trans for something like $300. Both were rebuilt, I got a NP231C transfer case from an S10 Blazer, and positioned the drivetrain where my old driveshafts would work. I didn't drive like a madman, so I wasn't too concerned with the Dana 30 and 35. I did actually source a set of Dana 44s to swap into it, but sold it before I ever got around to the axle swap. Legend has it they are still behind a shed at an ex-girlfriends house in Virginia...but I'm not crazy enough to try to go get them back. :lol:

It's really all about what you want to do with it, and what is legal in your area. For the cost analysis alone, if you could get away with V8 power, that's what I'd do. Probably what many others would do too.
 
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