4.0 question........wrist pin

[Jeep Driver]

I have a lead on a Cherokee and the owner claims it has a bad wrist pin. How common or rare is that and how do you think he came to that determination?

First I've heard of a wrist pin going in a 4.0 and I would think it difficult to identify.

[FrankTheDog]

What year Cherokee? I've heard of several 96 and 97's that had loose wrist pin tolerances.

I had a 96 myself that let loose at 85k. The piston just disintegrated around the pin. It was clacking for some time before it let loose. Usually if they made it past a 100k they wouldn't come apart.

If the xj is in nice shape, buy it cheap and put another motor in it.

[Jeep Driver]

http://knoxville.craigslist.org/cto/2653938653.html

[Eagle]

I have a lead on a Cherokee and the owner claims it has a bad wrist pin. How common or rare is that and how do you think he came to that determination?

First I've heard of a wrist pin going in a 4.0 and I would think it difficult to identify.

There's a possibility it's a crack in the flex plate, if it's an automatic.

 

Test: Start engine. Rev it up and down a few times in neutral (not to redline, just up and down slowly from idle to maybe 1500 or 2000 RPM. Listen for a knock.

 

If there's a knock, step on the brake, put it in gear, and apply just a little bit of throttle (just enough that the engine is pushing SLIGHTLY against the brakes). If the noise disappears, it's probably a cracked flex plate.