I have a 1990 xj renix with 170k and for a while there's been a knocking sound coming from near the transmission. At first I thought it was the flex plate but after going under there and tightening up the bolts with thread locker and finding no cracks, I can still hear the sound. Any ideas of what else it could be?

 

A common issue is the exhaust where it passes over crossmember. It could be making contact or the rubber isolator is worn out.

 

^^^^^ like Steve said, check and see if the exhaust hanger is worn allowing the exhaust to hit or tap on the crossmember.


Pic from Cruisers Tech pics

 

Just checked it out and everything looks solid there. Could it just be that the older cherokees have that sound naturally? Like I said I can't exactly remember when the sound started

 

Could also be worn motor or transmission mounts.
Is this a constant noise?
Only when driving or does it do this at idle?
In gear and in neutral?

 

Only below 1500 rpm. Does it no matter which can gear it's in and it seems to get quieter after it's been driven for a bit

 

My 01 is doing the sam thing. Sounds like a loose shock or suspension clunk coming from that area but I crawled under it today and rocked it but couldn't locate

 

hey man I have the same noise between transmission and engine. Sounds like a knock and the only difference is that I have a 2016. Only in park when warmed up. Did you ever find out what it was

 

Sfift linkage assembly and associated stuff?