Originally Posted By: 440Magnum
Originally Posted By: meep
The piston skirt issue seems to be more prevalent among folks that live north of 4000 rpm. I saw it happen with a family member's '94. He drove it like a slingshot and it put up with it for a while before grenading on a road trip.
I've read similar too. "Keep it below 4k" seemed a good rule of thumb.
M
There's absolutely no reason to spin a 4.0 above 4k, except briefly during passing. There's NO more power up there anyway- its a tractor engine, and should be driven like one. That's one reason I like the 5-speed stick XJ so much more than the automatic. With the stick you can just lug the snot out of the 4.0 and it loves it. The automatic is always downshifting and it just does...not...help anything. Except to make more noise and make the engine unhappy. The fact that the 4.0 isn't happy at higher RPM is a bit hidden, though, because like all inline sixes it remains glassy smooth at all RPM levels.
To be honest, I rarely even read about 4.0 piston skirt issues, but then I have zero interest in "mudding" and that's where the high-RPM failures of all 4x4 engines tend to happen. In rock-crawling- which I love- its all about idle to 2000 RPM and maximum torque. Mudding is definitely an application where a shorter-stroke V8 set up for high RPM would be a good swap.
Wide open, I'm not sure an automatic XJ will even hit 4000RPM. I think the most I ever had mine up to was 3500 and that was passing someone.
I'd love a stick 4.0. That is probably one of the easiest combinations to learn manual transmission on.
I do like my auto for rock crawling and wheeling in the woods. No toasting of clutches or juggling 3 pedals.
I'm not a huge fan of mud ... mainly because things break and the mud gets EVERYWHERE and rots your vehicle out. With that said, my skinny tires do a pretty good job of getting me through things without having to go balls to the wall.
2000RPM in 4LO 1st gear will dig and pull through anything (or dig and pull until I'm sunk to the doors).
99-01 or so 4.0s (early coil pack) have problems with piston skirts.
My parents used to have 4.0 5 speed wranglers. The 4.0 does sounds pretty sweet up high! ... high being 4000RPM
Thanks to an over active fan clutch, all I hear at anything above idle is the sound of a jet engine and a mechanical fan spinning way too fast.
Originally Posted By: meep
The piston skirt issue seems to be more prevalent among folks that live north of 4000 rpm. I saw it happen with a family member's '94. He drove it like a slingshot and it put up with it for a while before grenading on a road trip.
I've read similar too. "Keep it below 4k" seemed a good rule of thumb.
M
There's absolutely no reason to spin a 4.0 above 4k, except briefly during passing. There's NO more power up there anyway- its a tractor engine, and should be driven like one. That's one reason I like the 5-speed stick XJ so much more than the automatic. With the stick you can just lug the snot out of the 4.0 and it loves it. The automatic is always downshifting and it just does...not...help anything. Except to make more noise and make the engine unhappy. The fact that the 4.0 isn't happy at higher RPM is a bit hidden, though, because like all inline sixes it remains glassy smooth at all RPM levels.
To be honest, I rarely even read about 4.0 piston skirt issues, but then I have zero interest in "mudding" and that's where the high-RPM failures of all 4x4 engines tend to happen. In rock-crawling- which I love- its all about idle to 2000 RPM and maximum torque. Mudding is definitely an application where a shorter-stroke V8 set up for high RPM would be a good swap.
Wide open, I'm not sure an automatic XJ will even hit 4000RPM. I think the most I ever had mine up to was 3500 and that was passing someone.
I'd love a stick 4.0. That is probably one of the easiest combinations to learn manual transmission on.
I do like my auto for rock crawling and wheeling in the woods. No toasting of clutches or juggling 3 pedals.
I'm not a huge fan of mud ... mainly because things break and the mud gets EVERYWHERE and rots your vehicle out. With that said, my skinny tires do a pretty good job of getting me through things without having to go balls to the wall.
2000RPM in 4LO 1st gear will dig and pull through anything (or dig and pull until I'm sunk to the doors).
99-01 or so 4.0s (early coil pack) have problems with piston skirts.
My parents used to have 4.0 5 speed wranglers. The 4.0 does sounds pretty sweet up high! ... high being 4000RPM
Thanks to an over active fan clutch, all I hear at anything above idle is the sound of a jet engine and a mechanical fan spinning way too fast.
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