palehorsevt

Unfortunatly I missed by one year the 4.0. I have a 2007 4 door unlimited and was wondering if anyone had swapped out to the 4.0. Besides motor mounts I wonder if the tranny would be any problem..

Yes I would love to do a hemi but at $20,000 cant even think about it...

Thank You

JeepaRoo

the 4.0 was never used in the JK....

CAN it be done? im sure it could but all ofthe electronics from 2006 TJ to 2007 JK are completely different.... you would also need to measure to make sure the 4.0 would physically fit...

-Christopher

palehorsevt

Plenty of room as they used the 4.0 in the same frame in 2006. interesting about the electronics. Given the hemi swaps there obviously is some way around the "brain"...

AZJeeper

You are talking about the TJ vs the JK, right? The JK was completely redesigned from the TJ, including the frame. Maybe the engine would fit. Maybe not.

Try it an let us know!

Stuka

To the above poster, the frame in a TJ is in no way comparable to the frame in a JK.

You can fit a 4.0 in a JK. The JK was originally designed to house the i6. But economics didn't allow for it. As the 4.0 was only used in the Wrangler, and was too expensive to manufacture.

So, can the 4.0 fit? Sure. Will it be easy? Noooo. The mounts are the easy part. Its trying to make it work with the JK computer system that will be tough. Also, while the 4.0 has gobs of off idle torque, it is otherwise a bit underpowered for a JK due to their heavier weight. A super charged 4.0 would do ok though.

As for the Hemi swap, you can do it for WAY cheaper than 20k. especially if you get an engine that was pulled from another vehicle (cherokee, commander, etc).

Ryanc

Why would you want to do this?

DirtyKK

trade in your JK for a TJ

trentsjk

If you want a 4.0 that bad trade to jk, This would take a lot of coin to do. just let the 4.0 go.

Benchmark Designs Inc.

Nope.

2006 and earlier was the TJ with the 4.0L.

2007 and later was the JK with the 3.8L.

Completely different vehicles in every way. No common parts interchangeability.

Besides, the 3.8L makes more power and torque at all RPMs. The reason the JK feels underpowered is because it weighs a ton more than a TJ.

bigbluejk

Most places have laws against swapping in a motor older than what came in it. The 4.0 was a great motor, but discontinued in 2006. Your JK has to be at least 2007. If you don't care about legality, why not swap in something with 8 cylinders. I would do a small block chevy before a 4.0 myself. It isn't that hard to build a 400hp / 400+ ft/lb smallbock chev, and wouldn't cost much more than the I6 if any since you will be doing custom motor mounts, adapters, etc. etc. anyway and likely rebuilding the 4.0 with maybe a few minor upgrades.

Using a fresh 383 or sb400 with some trickflow 23 degree heads, nothing too crazy on the cam keeping the powerband lower rpm and a good fuel supply you could have power and torque close to a 5.7 hemi for about $2k with some smart shopping. If you were building something for sand dunes or something and could have power higher in the rpm band you could get closer to 500+ hp without much more than a cam swap.

I loved my I6 jeep engines of the past, but wouldn't consider a swap into a JK with one.