Atl JK

Yes, I wish it could stack up to the mighty 4.0l!

Seriously, the 4.0l is arguable the most over rated engine ever.

Stuka

That dyno sheet was originally shown in a JP Magazine review of the JK (where their biggest complain was the engine). It came directly from Chrysler, and is not a real dyno sheet, its a target that they were shooting for. The V6 in my JK will not pull well below 1000rpm. It bucks and sputters and eventually dies. With every 258/4.0 I have driven, they pull smoothly down to 400rpm. Which is NICE off road.

Something a dyno doesn't show is rotational mass. The V6 in the JK is *WAY* easier to stall than an inline 6. Not to mention an inline 6 is naturally harmonically balanced (the only engine that runs smoother is a V12). Plus, when you have 7 main bearings, and only 1 piston per journal, it makes for a very strong engine. The 4.0 (and the 258/232 that it was based on) has proven itself for the past 35 years as being an extremely reliable engine, known for having a lot of low end grunt. I have almost 250k miles on the 258 in my other Jeep, and it still runs extremely well.

I would gladly give up a few more HP at an RPM that I never use to pick up grunt at the RPM that I use the most.

Atl JK

The 4.0l was a good engine, but it had some issues later in life.

I will say that the 3.8l must be easy to stall. I've never stalled mine, but a few of my friends had issues stalling it all the time when driving it. I think they're just rusty driving a manual though.

uwisuwerme7

Mine stalls easily, but i'm super easy with the crutch.

TechJunkie

I had both a YJ and Cherokee Sport with the 4.0. Both were great engines and both became noisier and noisier as they move past 100K. It was and ever increasing tapping. Always ran strong and neither used oil. I would have to say that both "felt" peppier than the 3.8 but the 3.8 feels smoother. Very subjective I know but just my perceptions. I really liked the feel of power the 4.0 had and was considered by many a bullet proof engine.

On killing the JK, yes I have done this three times. For me it is the clutch. The engine is so quite if I have the radio on I cannot hear the engine and the clutch is so "soft" as I call it, that you don't feel it until you are almost all of the way out. On my YJ you felt the clutch grab as soon as it made contact and I could almost always hear the engine. My JK's clutch is so smooth that it is hard to feel the friction zone. I have had to learn to feel where my foot is when I hit it.

I haven't felt that the 3.8 is more stall prone because of torque or any inherent issue with the engine. If I apply the correct amount of throttle and clutch it moves along smoothly. The more I drive it the smoother it seems to get.

Just my $0.02 and not worth much more than that!

muddpuppy01

dont worry about driving in 5th I drove around 50 one way in 4th trying to figure out why my mpg was dropping looked down duh

people stall mine all the time hell I still do it but w/ 3.21 gearing and 37s what do you think is going to happen only thing I dont like about it is once you hit the stall point in the rpms sometimes takes a few seconds to stop so you can start it again

JKlad

On the stalling issue, I think I may have an explanation. Another thread on this forum was discussing the difficulty in clutch-starting the JK and the fact that you needed to really get it rolling, and the reason given for this is that the motor has a camshaft sensor that doesn't kick in and provide pulses to the ignition system and EFI 'till about 300RPM and provide ignition.

I'm guessing that this is the culprit behind the JK's stall issue. Normally when a vehicle shows the symptoms of a stall approaching, you just pop the clutch in, hit the gas, & wait for the revs to come back up again, and this will work even if it's literally at 100RPM with the drivetrain bucking. With the JK, if the revs drop low enough the ignition system just shuts off & she dies on the spot, whether you clutch it & give it gas or not and it's not possible to recover from the stall.

Anyone have any opinions on this as I'm just having a guess here & putting 2 & 2 together.

uwisuwerme7

That is one thing that I always found odd about the JK. I've had two motorcycles and two other manual tranny vehicles and if it was ever going to stall a pull on the clutch would save the engine. Not the case on the JK at all. Mine seems to act more like a squrrel in the middle of the road. The RPMs will jump up and down with the Jeep "bucking" whether i give it a ton of gas or clutch.

As far as the 3,000 RPM deal, mine only sees that range a few times a gas tank...
My shift points are between 1,800 and 2,200 in normal driving with 3.21 gearing.

CdnJeepDan

6th gear kind of scares the crap out of me too... I really wish they'd have put reverse beside 1st or 5th.

What does happens if you accidentally go into reverse instead of 6th? Does the transmission have a fail-safe to prevent it? Is there some method internally that would prevent it from blowing your transmission up or tearing the drive train from your Jeep?

Makes me miss my '04 TJ's 5 speed.

Weeds

You hit reverse instead of 6 you will back out real quick.

Did some driving yesterday where we have stop lights but the speed limit is 60 mph.

Starting in 2nd, winding to 3600 rpm, then to fourth and 3600 rpm then to 6th. Works just fine with stock Rubi.

I will take 4th gear to redline when passing on a two lane.