[ZLRob]

This just started either today or incredibly recently and I didn't notice it until today.
In reverse and reverse only I can hit the gas a little bit more than a feather and I'll feel a thump, almost like the CB is shot, or the rear end bushings are. I can duplicate it whether or not I hold the brakes while I try to give it some gas, but needless to say it's probably one of the more interesting things I've seen on this car so far. Especially because it's only happening while reverse. You put it in drive and try it and it's like nothing is going on at all.


Anyone had issues with bolts backing off the diff mounts, bad diff bushings, or a bad CB yet on their Z? 54K miles currently on the clock.


Haven't had a chance to peek under there yet while it's doing it and I'm not sure I trust anyone else to hop in and do that while I'd be back there.

[2023_ZL1-AUTO]

Driveshaft, or driveshaft connection at either end? I know before my Carbon Fiber driveshaft snapped, I was hearing a kind of thump when I would go from part to drive, but I did hear it a bit louder going from park to revers. It wasn't constant when the car was moving. But figure any info is better than no info ! Good luck!

[ZLRob]

Originally Posted by 2023_ZL1-AUTO

Driveshaft, or driveshaft connection at either end? I know before my Carbon Fiber driveshaft snapped, I was hearing a kind of thump when I would go from part to drive, but I did hear it a bit louder going from park to revers. It wasn't constant when the car was moving. But figure any info is better than no info ! Good luck!

Yeah it's gonna be either the DS or the diff mounts/ mounting bolts. It sounds weird I'll say that much. Sort of led me to this thread, which seemed oddly familiar to what I'm dealing with.


https://www.camaro6.com/forums/showthread.php?t=621360

[bishopts]

Is it in the rear? Kinda sounds like a noise you would get from an engine mount or trans mount.or like you said diff mounts. Carrier bearing could but you would also have a vibration on acceleration too.

[ZLRob]

Originally Posted by bishopts

Is it in the rear? Kinda sounds like a noise you would get from an engine mount or trans mount.or like you said diff mounts. Carrier bearing could but you would also have a vibration on acceleration too.

Exactly. The engine mounts are absolutely good and I just checked the CB here very recently and I don't do hard take offs like drag strip stuff so the chances of that thing getting wasted between the time I checked it and now is HIGHLY unlikely, especially since I checked it within the last 3-5K miles. The only thing that leaves is the trans mount and the diff. To answer your first question though, yeah, it sounds like it's coming from the rear. I give it some throttle when backing up, and if it's anything more than a gentle feather I feel this THUMP feeling.


The fact that no one offers a poly trans mount for these cars yet is mind numbing considering that they offer poly crap for literally everything else around the car.

[bishopts]

Originally Posted by ZLRob

Exactly. The engine mounts are absolutely good and I just checked the CB here very recently and I don't do hard take offs like drag strip stuff so the chances of that thing getting wasted between the time I checked it and now is HIGHLY unlikely, especially since I checked it within the last 3-5K miles. The only thing that leaves is the trans mount and the diff. To answer your first question though, yeah, it sounds like it's coming from the rear. I give it some throttle when backing up, and if it's anything more than a gentle feather I feel this THUMP feeling.


The fact that no one offers a poly trans mount for these cars yet is mind numbing considering that they offer poly crap for literally everything else around the car.

I guess check your bolts on all the control arms. Look for "shadows" of where you can see the bolt has slightly shifted.

On the impalas i see pretty regularly a pop noise in the rear from a bushing that is pressed into the knuckle that a control arm bolts to. I know it's a whole different knuckle but good info for diag.

[ZLRob]

Originally Posted by bishopts

I guess check your bolts on all the control arms. Look for "shadows" of where you can see the bolt has slightly shifted.

On the impalas i see pretty regularly a pop noise in the rear from a bushing that is pressed into the knuckle that a control arm bolts to. I know it's a whole different knuckle but good info for diag.

Yeah it may be a good time to start going through all of these bolts and checking them all for tightness at this point. It feels like the diff is thumping, however, we both know loose bolts emanate in weird ways even when it's not related to driveline stuff. Especially when suspension stuff is capable of making these odd noises as well.