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Swapping 3.8 to 4.0?

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Old 11-04-2010, 01:53 PM
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Originally Posted by 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
WTF? Why? Why not go back to the 2.5 4 cylinder??

This may take top honors for dumbest question of the year award.....Congrats.
Old 11-04-2010, 05:39 PM
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Originally Posted by Lt. Dan
Transmission swaps over, doesn't it?
You're right, forgot about that! Tcase too I suppose.
Old 11-04-2010, 05:59 PM
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Originally Posted by Benchmark Designs Inc.
You're right, forgot about that! Tcase too I suppose.
The transmission bolt pattern is different. The 4.0 uses the AMC bell housing pattern (Shared with AMC 304, 360, 390, and 401 V8's, and the 232 and 258 i6's). The Chrysler pattern used by the 3.8 is different.

However if he has a 6sp, the bell housing can be swapped, as TJ's did come with the NSG370 in 2005 and 2006. Although the input shaft may be a bit longer on the V6 version compared to the i6 version used in the TJ's.
Old 11-04-2010, 06:09 PM
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Originally Posted by 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.
First thought when the topic came up. While against the law, not sure if anyone would know.
Old 11-07-2010, 08:26 AM
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This whole thread should be deleted.
Old 11-07-2010, 09:57 AM
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Originally Posted by Uneasy Rider
WTF? Why? Why not go back to the 2.5 4 cylinder??

This may take top honors for dumbest question of the year award.....Congrats.
63 Posts hardly gives you voting rights

Back to the subject. The 4.0 seems to have a reputation of being the master of motors, I had Jeeps with the 4.0 and loved it. But my JK weighs 5440lbs with tools, gear, gas and Me in it The 4.0 would be searching for power to drag my JK around. The 4.0 sadly will never be a viable option for the JK, Remember that most trail driven TJs have been regeared if they go over 32" tires. Compare a TJ with 37's with my JK with 37s, 4.88s and 5.13s are the norm for both and the TJ is 800-900 pounds lighter.
Old 11-07-2010, 12:25 PM
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What about the 4.0 V6? It's in the same family as the 3.8?

It makes a bit more power, but probably not enough to be worth a swap.
Old 11-07-2010, 12:44 PM
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Originally Posted by desync0
What about the 4.0 V6? It's in the same family as the 3.8?

It makes a bit more power, but probably not enough to be worth a swap.
As I recall the 4.0 is in the same family as the 3.7L. So it would not be a direct bolt in.
Old 11-08-2010, 01:51 AM
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The 4.0L V6 is a stroked 3.5L.

The 3.7L is based on the 4.7 V8.
Old 11-10-2010, 07:45 AM
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The Grand Caravan has a 3.8L and has a 4.0L option so they cannot be that much different.


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