Thud in the back normal?

[Level300]

I installed the z28 suspension kit several weeks back and I have a question for you guys.

I know the suspension is tight and driving over roads with a lot of patches can be fun. But it is normal to occasionally hear/feel a thud coming from the back going over a certain type of bump?

It’s not a real jarring thud but it is pronounced. It’s hard to pinpoint exactly what type of bump causes this thud and it doesn’t happen all the time. It happens when going slower maybe under 30-40mph(?) and only on rough roads. I can’t seem to duplicate the conditions when this happens and it’s somewhat rare when it happens. The rear end is as tight as the day I installed the suspension. I also did a track day and it performed without any issues. I checked all bolts and everything seemed fine. Going over driveway curbs, backing out the driveway is also fine.
I have solid cradle bushings installed and suspension bushings were timed if that matters to anyone.
Thanks!

[Biergut]

Originally Posted by Level300

I installed the z28 suspension kit several weeks back and I have a question for you guys.

I know the suspension is tight and driving over roads with a lot of patches can be fun. But it is normal to occasionally hear/feel a thud coming from the back going over a certain type of bump?

It’s not a real jarring thud but it is pronounced. It’s hard to pinpoint exactly what type of bump causes this thud and it doesn’t happen all the time. It happens when going slower maybe under 30-40mph(?) and only on rough roads. I can’t seem to duplicate the conditions when this happens and it’s somewhat rare when it happens. The rear end is as tight as the day I installed the suspension. I also did a track day and it performed without any issues. I checked all bolts and everything seemed fine. Going over driveway curbs, backing out the driveway is also fine.
I have solid cradle bushings installed and suspension bushings were timed if that matters to anyone.
Thanks!

No.

The Z/28 does not have any thuds on a correct car. There are pops and associated noises from our Torsen differentials, however, I don't think this would apply to you unless you've also installed the mechanical diff.

[HoodCheck]

Normally its fine, but if you were to hit a pothole, that'd do it... Or if you bought used, perhaps you got a bad component.

[Level300]

Originally Posted by HoodCheck

Normally its fine, but if you were to hit a pothole, that'd do it... Or if you bought used, perhaps you got a bad component.

No, everything was brand new. It was drop shipped from a gm dealership. Thanks.

[Level300]

Originally Posted by Biergut

No.

The Z/28 does not have any thuds on a correct car. There are pops and associated noises from our Torsen differentials, however, I don't think this would apply to you unless you've also installed the mechanical diff.

No, I have the 1LE diff. Thanks.

[Biergut]

Originally Posted by Level300

No, I have the 1LE diff. Thanks.

Then, and believe me with no disrespect meant, sounds like something is just not installed correctly or potentially not tightened properly. I can only relay that there are zero thuds of any kind from the back of my Z/28 and this includes some hard humps and bumps encountered on race tracks, etc.

[Level300]

Originally Posted by Biergut

Then, and believe me with no disrespect meant, sounds like something is just not installed correctly or potentially not tightened properly. I can only relay that there are zero thuds of any kind from the back of my Z/28 and this includes some hard humps and bumps encountered on race tracks, etc.

No worries man. Sounds like I overlooked something. I appreciate all your help.

[SIM GhostrdrZ]

Originally Posted by Level300

No worries man. Sounds like I overlooked something. I appreciate all your help.

We could spend a lot of time troubleshooting the thud. Does it come from one side vs another(struts). Did you put dssv struts on and SS springs? Or did you retain your struts and springs and they don’t like something now. Did the thud come over a few miles of driving, then you might want to retorque everything, which is common when replacing everything.
These Z28’s are solid as mentioned.

[SIM GhostrdrZ]

Could it be something else loose in the rearend? Spare tire, jack, battery, etc. I just hate sounds that aren’t suppose to be.
I feel your frustration

[Level300]

Originally Posted by SIM GhostrdrZ

Could it be something else loose in the rearend? Spare tire, jack, battery, etc. I just hate sounds that aren’t suppose to be.
I feel your frustration

I installed the full z28 suspension. I pulled and replaced all the parts. No mismatched parts. I can’t tell exactly where it’s coming from but it’s definitely coming from the back. It’s been there since the beginning, I think. I was really careful with torquing everything down and took my time, just like what I did with the front. It’s not getting any worse so that’s good. I have a wireless camera that I’ll mount back there to see what’s going on.

I really appreciate all your help. Thanks!

[69L48Z27]

I thought some people reported an ‘oil can’ noise? I don’t have it in mine, only noises for me are some clicks and pops for the rear end.

[DAP_Driver]

Is it the LSD?

[pzero]

Originally Posted by Level300

I installed the z28 suspension kit several weeks back and I have a question for you guys.

I know the suspension is tight and driving over roads with a lot of patches can be fun. But it is normal to occasionally hear/feel a thud coming from the back going over a certain type of bump?

It’s not a real jarring thud but it is pronounced. It’s hard to pinpoint exactly what type of bump causes this thud and it doesn’t happen all the time. It happens when going slower maybe under 30-40mph(?) and only on rough roads. I can’t seem to duplicate the conditions when this happens and it’s somewhat rare when it happens. The rear end is as tight as the day I installed the suspension. I also did a track day and it performed without any issues. I checked all bolts and everything seemed fine. Going over driveway curbs, backing out the driveway is also fine.
I have solid cradle bushings installed and suspension bushings were timed if that matters to anyone.
Thanks!

Thud in the back normal? No it's not normal something is off or something is loose.

My Honda CRV has the same issue. Got brand new struts with coils installed and it makes small thud x 3 noises when going over white line dots and other uneven roads. On a free way it drives smooth with no noises. On regular road it drives smooth with no noises. Only when going over bumps or uneven roads. Something is off. Never had that issue with my old struts except it was bad and waved up and down a lot going over uneven roads. Now the new struts drives tight, but small thud x 3 sounds is making me mad. Took it back to the dealer and they checked everything all good. I guess it's just the nature of the beast. Put something or replace parts that's not original, and you're going to get something off.

Good luck and hope you find it.

[DAP_Driver]

Not to hijack the thread but I also have a popping/clicking sound when I make turns at very low speed ie right turn from a stop sign. 100% stock ‘15 Z/28. I heard it may be the diff? Anyone else experience that?