Clunk or knock when coasting/stopped...

[sevenhelmet]

OK, here is a random noise for anyone with insight...

2003 KJ Sport, 5-speed manual, stock engine/drivetrain

First off, my Jeep is running just fine, engine oil and all driveline fluids recently serviced. I've had no issues with the engine or transmission, the clutch does not slip or grab, and the only recent "fix" was replacing a hose clamp on the evap emissions canister to fix a nuisance engine light.

However, when I am driving for 10-15 minutes (enough to warm up the engine and drivetrain) and then come to a stop in traffic or put the clutch in to coast down, sometimes I will hear a single "clunk" or "knock". It sounds like somebody knocking lightly on the dashboard with their fist. It isn't loud, and it is only a single knock, but sometimes I will hear it a couple of times while stopped. A "knock" and then a few seconds later, another identical "knock". I thought at first it was something in the suspension, but I later noticed that it only does it when I have the clutch on the floor and I'm either slowing down or stopped. No check-engine light, no change in RPMs, and no associated clutch slippage or grabbing. Mileage and everything else is normal. Right now this is just a noise.

Any ideas on what this could be?

 

[Cardhu]

Do you have any vibration? Thinking u joint, tis the season. Touch it after a drive and see if its hot.

 

[sevenhelmet]

I haven't noticed any unusual vibration. It only makes the "knock" sound when the Jeep has had a chance to warm up for at least 15 minutes- I never hear it on a short drive. Perhaps a U-joint gets loose when it turns for a while and warms up? It's been doing this for about a year with no change that I've noticed. It isn't something I particularly worry about, but maybe I should... just trying to narrow down the possible root causes.