Jeep Liberty 4x4 review

[Hokiefyd]

My family has owned three different 4.0L engines (in an '88 XJ, in an '89 XJ, and in an '06 TJ). We've also owned a 3.3L and a 3.8L in minivans. I choose the V-6 every time. I think the 3.8L works better in the heavier JK that my neighbor has than the 4.0L ever did in the '06 TJ. It just had no guts at all. It was REALLY bad before dad put the larger throttle body and Borla header on it. I'd call it just "passable" after those mods. The 3.8L in my neighbor's JK is bone stock, and even on 35s, it pulls it around well.

I dunno...maybe our 4.0L was a particularly weak example, and maybe the 3.8L next door was a particularly strong example.

 

[SwampSurvivor]

I have had the complete opposite experience (and almost everyone that goes from a 4.0 to a 3.8 will agree).

Likely, most of the experience that the 4.0 is peppier is from the actual throttle cable.

But, with that said, I am running the EXACT same tires on my Cherokee as my parents had on their JK.

3.55 Gears, Auto Transmission and 120K miles - my Cherokee has no problem maintaining 55 or even accelerating.

My parents JK Rubicon with the SAME EXACT tires, couldn't maintain 55 on flat ground in 6th gear. The only time it could use 6th gear was going down hill.

The only way to accelerate from a stoplight and keep up wtih traffic was to wind it up to 4K rpm. The old 4.0 could do it, easily, below 2500.

The 3.8 is a rubbish, underpowered engine, in my experience.

Lot more fun to drive, though. Never had to wind up the 4.0 and shift all the time. Their 04 Rubicon didn't even need 1st gear - it could take off in 2nd all day unless you were on a steep hill.

I would like to test drive another 3.8 6 speed to see if they are all that bad.

My Cherokee with 31s and 3.55 gears has no problem accelerating and keeping up with traffic without needing to red line. Unfortunately, I can't go above 3000RPM because the fan clutch causes the belt to slip.

I'm not saying the 4.0 was perfect. It didn't have a lot of power up top, did have a habit of dropping piston skirts and cracking heads (all year susceptible to it), drank gas and liked to mark its territory.

IF the 3.8 didn't have the bearing problems, you could run a cable to the throttle body *and* you could get rid of the sub-par chrysler electronics, I'd be first in line for an 07JK for a toy. I still may consider one.

Aside from engine and electronics issues, the JK is much better in every other aspect than what it replaced.

It rides MUCH MUCH better on the road, but, is MUCH more capable off road. The "long arm" suspension (longer arms than a TJ) just does everything better. And they can fit much larger tires from the factory. And I can comfortable fit in one.

 

[440Magnum]

There's no question that the 3.8 has a bit more power on tap, breathes better, and is ever-so-slightly newer in design... but the difference isn't huge and almost exactly makes up for the extra weight of the JK. Perceptions can be funny. I was very impressed with the way the 3.8 in the rental JK 4-door I had in Hilo last summer worked. It moved that big 4x4 JK around almost as smartly as the 4.0 hauls my two much lighter XJ's, and it did so with the old 4-speed automatic.

Fact is, the 3.8 and 4.0 were designed within a couple of years of each other in the 1980s, and to very similar requirements. The 3.8 was built for hauling heavy minivans, and the 4.0 was built (at AMC) specifically for the XJ and YJ. The 4.0 has more torque right off-idle and is smoother (being a straight six), but the 3.8 has more total power and is a much smaller package.

Its a testament to how good the 4.0 was/is that Chrysler engineers really, really embraced it and quickly improved it a TON by putting Chrysler engine management on it, resulting in the "HO" vesrion. Bill Weertman really spoke well of it (and its little-brother 2.5L 4-banger) in his Chrysler engine history book. Chrysler has always been an engine-focused company, and to have Chrysler engine guys fall in love with the 4.0 is about as strong an endorsement as can be made. But all things get passed by advancing tech, and that happened to both the 4.0 and 3.8.

When Chrysler realized they had to get rid of the length of the 4.0 in order to meet more stringent crash requirements on engine intrusion into the passenger area, they looked at the rest of their lineup for an engine with the closest specs to the 4.0, and the 3.8 was the obvious choice over the V8-derived overhead-cammed 3.7L. (this from comments from the Jeep/Truck engineers made on a Jeep forum).

Of course its now all OBE with the 3.6 now powering them all.