2.3 to 4.0 swap

[Jeff Rodgers]

Wanting to swap a 88 4.0 engine that was matched with an automatic with a 4 speed  from an 88 with 2.3. Will flywheels need changed ? Will the manual bellhousing with clutch and pressure plate bolt up to the 4.0?  The 4.0 was from a 88 Cherokee and the vehicle that  it is being installed in is a 88 Comanche and was already previously a manual. 

[eaglescout526]

2.3? Do you mean the 2.5L?

 

If so, the swap isnt worth your time for minimum power gain. And nothing from either engine swaps to each other so youll need a donor vehicle that has a manual to swap in. 

[fiatslug87]

14 minutes ago, eaglescout526 said:

the swap isnt worth your time for minimum power gain.

Spoken like a multiple 2.5L owner.

[eaglescout526]

8 minutes ago, fiatslug87 said:

Spoken like a multiple 2.5L owner.

Haha! yup, guilty. 

[89 MJ]

You’ll need the trans from the 4.0 Jeep too. Bellhousing was different between the 2.5 and 4.0. Though if you aren’t happy with the power of the 2.5, I think you’ll be disappointed with the 4.0 after doing all of that work. 

[Eagle]

On 5/23/2026 at 9:20 PM, 89 MJ said:

Though if you aren’t happy with the power of the 2.5, I think you’ll be disappointed with the 4.0 after doing all of that work. 

 

WHAAAAAAAAT ?????

 

The difference is VERY noticeable.

[89 MJ]

1 minute ago, Eagle said:

 

WHAAAAAAAAT ?????

 

The difference is VERY noticeable.

Didn’t say that the difference wasn’t noticeable. I am saying that the effort of swapping the engine, trans, driveshafts, and engine wiring is a ton of work when there are other engines you can swap in for similar amounts of work. 

[GonzoTheGreat]

If you swap to a 4.0, you don't need to make custom motor mounts, crossmember, tranny mount, exhaust, standalone wiring, etc. like you would with a different drivetrain. You end up with a good, reliable engine thats engineered for that chassis.

 

Also if youre completely devoid of any load, on flat ground, and not crossing 55mph, there is not much difference in pull between the 2.5L and 4.0 because the 2.5 has deeper axle gearing, but under ANY normal driving condition the 4.0 has LOADS more power, and gets as good or better fuel economy.

 

I have a 2.5 and a 4.0. I like them both for what they are, but I would say if you have a good deal on a donor vehicle, and you plan to do more than just drive around town, I wouldn't hesitate to swap up.

[Eagle]

A friend of mine across town has a Wrangler TJ that he bought used with a 2.5L 5-speed. He put in a lift and runs rather large tires -- bigger than 32, probably 36s if not 40s. Nice Jeep, but it was a pig.

 

His stepson had another TJ, same year, but a 4.0L 5-speed. The body and frame on the stepson's Jeep kind of ... ceased to exist. I helped him swap the entire drive train from the stepson's TJ into his. The first time he drive it with the 4.0L in it he just about lost his mind. He couldn't believe the difference it made.