Sounds like someone's popping corn with marbles when in D

Stock 99 XJ 4.0/AW4/NP231 164,000 miles

As the title states when my Jeep is in drive there is a banging/knocking that seems to be coming from underneath the trans/transfer case shifters but only when it's in drive. I can feel it in my feet when driving. Pattern to the sound is a little like popping corn, doesnt really appear to change with throttle inputs. It has been getting progressively worse over the past week so I imagine something is loosening up. The Jeep just made a 2000+ mile drive across the country no problem. Runs perfect, shifts fine, 4wd is fine. This just started a week or two after the drive. Any ideas on where to start with this issue would be greatly appreciated. Thanks in advance for any help.

Does it do it when you shift into Drive but are not moving? Does it do it in reverse?


The first thing I would check would be flex plate to torque convertor bolts.

Loose torque convertor bolts or cracked flexplate would be where I'd look and put my money.

Agreed. I'd bet on either that or the flexplate cracking.

I would set the e-brake, securely chock the wheels (preferably roll it up against a curb or something), put it in drive, and have a listen from outside and/or under the vehicle. If you have someone you trust around, you could have them hold the e-brake and service brakes instead, I usually don't.

Where are you located? If it ends up being the flexplate I have at least two good spares in my storage unit in Auburn that I really don't care about.

It does it in drive when I'm not moving but not in park neutral or reverse. It makes a quick rattle when I start it too.

Kastein thank you so much for that offer but I'm actually out in Colorado now.

Sounds like it could also be a loose, worn, or missing exhaust mount as well.

Yeah sounding more like it may be an exhaust thing. Thanks for all the responses now I'll have a better idea of what to check when I get underneath.