I have a '99 TJ. I hear a loud clunk-clunk when I get up to 35 miles per hour. 35 miles per hour in gear. No noise when coasting.
I put my jeep up on jack stands and listened. It seemed to be coming more from the driver wheel than the passenger wheel. I pulled it off and found nothing clunking around in the brake drum. I've pulled out the drive line. The Universal joints are fine. I'm going to pull the cover off of the differentail and take a look inside.
I have the jeep "track lock" in my back diff. I think it's been worn out in some time. I wounder if this noise has something to do with it.
I'm not much of a mechanic, so any suggestions you have could assist me greatly. My wife totaled her car this week so I need to fix my Jeep without the help of a professional if possible.