Rubicon John

I love driving my wife's XJ. It's an auto, but it is WAY more responsive than my JK and it has 100K more on the clock.

Come to think of it, her XJ was also a lot quicker than my 03 Rubi with a 4.0 L & NV3550 manual.

highoctane

Going to a 4.0 would be a waste of money and be just as much of a dog as the 3.8. The JK is heavier and bigger in every way.

JeepDude90

ive had a 97 with the 4.0 and i have my jk and i dont mind both engines theyre both pretty decent engines, but the 4.0 was a much better built engine.

Ario56

I cant wait to show that graph to my buddy with an '06. Always ragging on the mini-van motor.

goaterguy

Yes but this thread is about the 4.0 vs. the 3.8. Nobody is arguing the V8.

Who has a 400 hp turbo 4 from the FACTORY? Chrysler has the SRT4 engine.

Nobody seems to remember the 4.0 long ass starting problems, or the gunk accumulation on the head cover...

Goeagles88

The JK is bigger and heavier in every way. The old 4.0 with a 3 speed auto (I had one) was an absolute dog. It would do 70 at over 3000rpms, but it didn't like it. It was also an antique engine in that it's emissions and build cost were higher. Going to the 3.8 makes sense from a cost and CAFE requirements standpoint (2 more mpg and cleaner emissions). Both engines are OHV engines. Most new engines are OHC. The big row has always been that OHV engines are better at low end torque and OHC engines produce better horsepower.

I am personally happy with my setup. Re-gearing after 35's helped a lot. I would like more power, but I don't really need it. I'd just get speeding tickets that would take money away from my mods account.

BKGM Jeepers

As previously stated, the JK has 20 more hp in stock form, but less torque. Torque is the important stat for off roading and that "ooomph" feeling during acceleration.

The JK has a v-6 because of crash test requirements. The 4.0 I6 was too long. I know the problem isn't emmissions because my 4.0 is zero or near zero across the board in smog tests (I have a TJ and a JKU currently).

My JKU is probably 800 lbs or more heavier than my TJ. Either engine would be marginal from a performance standpoint, but I bet the 4.0 would be superior off road...

cyberfalco

The only thing I can think of that would make me want to go back to the 4.0L would be the thought that it is "truck" style engine and not a car/minivan engine. It would make me feel that it would be more durable.

But, I am not really disappointed in the 3.8L. It felt good on the trails last weekend and my trip from Conway, AR, to Chicago, IL, two weeks ago was pretty comfy in my JK. There didn't seem to be any less power on the freeway in the JK than there was in my LJ.

Noxian

You might want to read back

https://www.jk-forum.com/forums/atta...3&d=1231786912


The 3.8 has more torque and HP,

I came from a 04 TJ Rubicon, and find no difference in power. Both were manuals.

I do notice the 3.8 is smoother and quieter and makes it sound like it isn't doing anything but it it has plenty of power.

The engine does feel very different due to the hydraulic clutch, and fly by wire, but its still very responsive. It just doesnt have the old clunky sound my TJ had, which even though made you feel like your driving a rough and tumble vehicle there was not real advantages

And with the issues that were starting with the 05 and 06 4.0 liters engine related to their crank position sensors and cams and lifters the 4.0 wasn't as reliable as it once was...