88 Cherokee Piston Slap? Nope, Cracked Flexplate

Well. That certainly could make a slapping-like noise.

 

1998 jeep cherokee salvage
Want me to go grab this for you?

 

Interesting.
I'm so intrigued by this, I wish I had time to run down there and check it out with you.

I went back and listened to the first video again. It really does sound like an external vibration. Like an issue with the torque converter. It just runs too quietly and smoothly in between knocks to point towards a rod or cam issue, IMO.

 

I just texted a buddy of mine who knows those engines a link to that video. His immidate response was "The starter is loose and knocking on the block."

Any chance you checked that?

 

Is there any discrepancy between the movement of the crank and the flex plate? If the crank-to-flex plate bolts were loose (or the flex plate-to-torque converter bolts) you'd get a knock like that, plus a resonating knock while running, like you have. Squeeze a wrench up in behind the flex plate to make sure the bolts are tight. They can back out if threadlocker isn't used.

I guess it could be a bad or non-existent rod bearing, but it doesn't make sense why you wouldn't hear it constantly.

Scotty, beam me down to Focker's coordinates.

 

Did you read the comments? His issue was bolts missing/loose from crank pulley. But he also replaced the flex plate, soooo... who knows.

BTW, don't run your engine like that, with the TC unbolted. It will make a mess of the crank.

There are three bolts that hold the TC to the flex plate. They go into the TC through the flex plate from the engine side. You have to spin the assembly to get to them one at a time. Usually you can only get to them with an open-ended wrench, which is why they can come loose. They are hard to get tight enough.

 

I think the TC in that last video was seperated to try to diagnose a problem. Find out if it was engine or transmission. Without the trans spinning, it must be on the engine side.