Hey guys, been a long time since I posted anything last. I am wondering what is the main difference between the 3.7 and 3.8l engines. Would I be able to get parts for my KJ from the newer 3.8 from the wranglers? Headers and programers whatever would get more power and torque out of my rig would be good. Not doing anything to it now, but looking to do some upgrades in the near future.

Thanks
Rudy

2 completely different engine platforms,parts will not swap between the 2 and a 3.8 programmer will not work on a 3.7.

Well that sucks, there is nothing I can put on this thing to get more power out of it. I know there are some headers for the 3.7 out there just have to look for them again. Maybe ill just keep with this engine till I break it and get a 3.8 with a new ecm later on. haha! Do you know if the auto trans from the kj will bolt up to the 3.8 block?

Pretty sure no one the trans, could be wrong.. But why're you so enthused with the 3.8? Someone makes headers for the 3.7, last i knew some were fs here by a member (see fs section)

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Patriot Blue 04 KJ
OME HD lift w/ 1/8" Clevis lift
LT 245/75/16 Revo's
Husky liners
Aeroturbine 2525
Amsoil

The 3.7 is worlds ahead of the 3.8 in every aspect.

3.7 makes more HP & torque with a better power curve..... The best thing about the 3.8 is that there are thousands of Grand Caravan/Town & Country minivans with the same motor in junkyards should you need used parts...

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LOST # 633
'05 KJ 3.7L/6spd/241 245/75/16 MT's
'88 MJ 4.0L/AW4/231 SWB HPD30 & trac-loc D44 w/3.73's
A dirty Jeep is a happy Jeep

The 3.7 is 10x better mill than the 3.8. Trust me I have both, and you want to stay as far away form that minivan engine as possible.

The Trans is the same between both though.

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- Mike
'12 JK

Jeep Tech Files

Thanks guys, yeah staying away from that minivan engine. I was just figuring the way mods go, more people will make the parts for a wrangler engine before they go and try working a Kj engine.

The 3.7 was actually made for the dakota/Ram line originally. I don't think it is still available in the Ram, but it was until just a couple of years ago.

I know that bragging rights are cool, but I question the need for any more horsepower in a KJ. All you will do it render the driveline more likely to break. Even for mall crawlers.

I had a 1981 CREW CAB Chevy C30 long bed pick-up with a 350/4v engine. That vehicle had 160 hp and 260 #'s of TQ. I towed a 7,000 car/trailer combo for ten's of thousands of miles, and the truck weighed almost 1,200 #'s more than the KJ, which has 210 hp and 230 #'s of TQ!!!!!!!!! Amazing that people can't get by with the KJ's power...

The one advantage the truck had was 4.56 rear gears. If you want more performance without destroying potential dependability and longevity, a gear swap is a much smarter, probably cheaper, and less impactful mod.

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LOST # 633
'05 KJ 3.7L/6spd/241 245/75/16 MT's
'88 MJ 4.0L/AW4/231 SWB HPD30 & trac-loc D44 w/3.73's
A dirty Jeep is a happy Jeep