Waldo_88

Alright, so I know there are going to be a hundred different thoughts/opinions/possible reasons for this but my 08 JKU is making a horrible clanking noise when I let off the gas. What throws me off is that some days it will happen every time I let off the gas and other days I can't get it to happen at all. The seems like the sound it coming from the rear, (Diff, driveshaft, transfercase area) it is hard to pin point. This sound only happens when I am coasting, including the second between gears, and after coasting when I hit the gas again for a second or two. When I am coasting it doesn't matter if the clutch is in or not, and the rate of clanking does change with speed. I am not a mechanic but have done all of the work on my Jeep so far and everything looks pretty normal. I took the rear diff apart and it looks brand new, and replaced the fluid while I was at it, it made no difference, U-joints look normal, and the fluid in the T-case has been changed recently as well. Thanks

08 JKU
Manual
Stock 3.73 Gears
37's
Open Diffs
4" lift

ShutterBug

Did you look at your breaks? I've heard similar noises on cars I have owned and it turned out to be a bad brake pad. Just a thought.

Waldo_88

Haven't looked at the brakes but they seem to work fine and it would be surprised if that noise was due to them. Especially if it doesn't change with the brakes are applied.

7kings

I'd also check the bolts on your shocks to make sure they're tight. They can make a good clunking noise if they're loose.

stevo1371

Are your u-joints good and solid? If not that I once had a broken spring right at the bottom where it sits in the axle. That was a similar description to what you described.

BlikitSchmikit

My rear brakes went bad and I recall having an odd noise coming from the back somewhere - (at the time) I didn't think it sounded like the brakes, more like something was seriously wrong with a bearing or something on the back/right side.

OH9JK

Typically I would start with a U-joint or bad bearing in your drive line but since you have checked those...double check your lug nuts are torqued to spec. Also go over all the components on your suspension lift including the shocks. Worn bushings or joints can get noisy.

Waldo_88

Suspension looks normal, u-joints look normal, lugs are tight, driveshaft has the normal, tiny bit, of play in it. When I push sideways on the rear tires I get a similar sound, I'm not sure if that's normal or not? I thought axle shaft but I think it would make noises when on the gas as well. Would a t-case make these noises?

jeeptk93

Sounds like an exhaust manifold.

Waldo_88

No way, it's definitely in the rear somewhere. It's definitely a metal on metal sound. It's been like 5 degrees all week but tomorrow looks promising hoping to get it in the air and everything tore apart