Low speed thunking from rear driver's side suspension

Only happens when I'm creeping along over a rough area.  I've pushed down on the fender to check the shock rebound - it's the same as the passenger side shock.  I've checked the nuts at the top, in the trunk.  Everything's tight.  I thought that might be the problem since I pulled the rear STB out around the same time I noticed the thunking, but I don't see any problems.  Maybe a Rancho is going, but I'm not seeing any sign of it in the shock rebound.  I've glanced at the bottom of the shock, but see no problems in that area.  I haven't touched anything to see if it's loose or not yet (it's cold out there!).

The car drives fine.  If not for the thunking, I'd have no clue there was anything wrong.

Perhaps the shock mount is failing (only 94,000 miles, but it's nearly twenty years old).  Or could another suspension component be the culprit?

Check the rear adjustment links. The heim joint boots could be dry and worn.

Check that a rear spring isn't cracked.

Also don't rule out chucks of ice or frozen snow that can lodge in the suspension and create noise.

Jack the R wrote:

Perhaps the shock mount is failing (only 94,000 miles, but it's nearly twenty years old).

This

You took the rear STB off, and it started thunking. Absolutely possible that the STB was holding it nice and tight.

I took the wheel off and looked everything over.  I didn't see any obvious problems.  The shock mount looks good.  I think I'll swap the shocks and shock mounts and if the sound is suddenly on the right side instead of the left I'll know where the problem is.

Woohoo, the thunking is on the passenger side now! New shocks for me!

Could be the sway bar end links. (do you have a rear sway bar?)

I swapped the shocks and the thunking moved to the other side, so I'm assuming that means the problem is with either a shock or shock mount.

I've got the stock rear sway bar.

There are some grommety bushing things on what I would guess is called the rear trailing arm - and if that's wrong I'm sure you can figure out what I mean - which have cracked open. I'll have to replace those too, but the shocks come first.

Jack the R wrote:

Woohoo, the thunking is on the passenger side now!  New shocks for me!

And mounts, shop around they are not too much $$ if you buy them right, try one of the online places.

I ordered Moogs from RockAuto. Surprised at how cheap they are compared to the strut mounts!

Jack the R wrote:

I ordered Moogs from RockAuto.  Surprised at how cheap they are compared to the strut mounts!

No big surprise there, actually. The Riv rear mounts were used on various GM cars from 1995 to 2011.

By the way if for some reason your mount covers are missing (rubber caps that go over the mounts, in the trunk) a number of them fit, you can go to a pick-n-pull near you to graba pair off any number of GM FWD cars. I got a pair from a Cavalier.

Well whoop-dee-doo, FedEx says they delivered my package yesterday, and it is nowhere to be found. Has anyone worked through RockAuto's order status and returns page? It's a little confusing. There's no option for "package not delivered." I think you're supposed to go through each item one by one and report it missing, and on the last item, you're supposed to check a field that amounts to "no more items to report missing," but isn't labelled that clearly. Then they contact the carrier to work out the screw up. Because I have other things to do, I believe I've messed up on the reporting process. I reported the shocks last night and thought I had properly indicated the "whole package missing" part. Today they've got the shocks marked as "not returnable." Does that translate to "you're shit outta luck buddy?" So I reported the mounts and the hood supports I ordered, but I messed up and checked "more parts to report missing" instead of "no more parts to report missing." Unfortunately I can't find any way to go back and edit this stuff. What a mess! I guess I'll try their email address and see what happens.

You'll probably have better luck giving them a call than trying to sort all of that out through e-mail.

Could be but it's not easy when you're working.

Yes calling is best, but Ive had no issues with their email support. I hope they get it worked out for you.

If it helps, Fedex once reported to me something was delivered and I couldnt find it. It showed up the next day.

I would suspect the sway bar bushings and or sway bar links. Bushing noise is not uncommon when the bushing clearance increases with age and ear. Cheap to fix. The bushing losses its elasticity sometimes and the bar will thunk in its holder, evane if it looks or feels good it can still be the culprit. I have wrapped the bar in tape and reinstalled the bushing as a test before. The tape takes up the slack