I have a 96 Cherokee classic 4.0 4x4 with 250,000 miles. I went to start it one morning and it made a nasty knocking noise, it didn't alter the driving at all shifts just fine, no shaking etc. Now it makes this knocking noise at the start up and while it is in park. When I shift to Drive Neutral and Reverse it doesn't make the noise.
Any ideas what this could be?

 

I know I already commented on the other post, but I can add a bit more. If your flex plate bolts check out, and the plate isnt cracked, try checking your exhaust mounts. If some are broken you could have your muffler rattling.

 

X2

 

I had my whole exhaust replaced in Dec 09, but today I'm going to check out the flexplate. Thanks again for your help.

 

Well that's what it was, as soon as I took off the inspection plate 3 of the 4 bolts where loose. Checked it out, tightened them up and now my Jeep sounds brand new not like a "lawn mower" as my dad said.
Thanks again guys!