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Greetings, proud new Oldsmobile 1971 Cutlass Supreme owner here :-)
I just registered on the forums so my apologies if I post to wrong section.
My vehicle is making some weird noises on rear end when hitting a pothole for example. Also vice versa even a small rise on the road causes it. Especially when there is more than one passenger.
The noise is a rapid "trrrrrrr" sound and otherwise there are no similar bad noises when the going is smoother. A friend of mine thought it could be related to ball joints.
My knowledge of cars is rather limited but please let me know if there is any other information I can provide!
If the noise is emanating from the rear it isn't ball joints which are contained in the front of the vehicle. Check the rear shocks & rear control arms for loose hardware. It could very well be shocks are completely worn out and with no compression in the shocks, they'll easily make a noise over potholes.
Thank you for the quick answer! I will check those.
Now that you mention it the noise sounds like something reaches its end and is more like rubber rather than metal hitting metal.
I had the car inspected today and there was no mention about this issue on the final document. However as I said the noise is much louder when there are passengers. The inspector was alone in the car when he ran tests.
Many (probably most) '71 CS vehicles did not have a rear sway bar. Your first order of business is to validate if you have a rear sway bar. It's possible it was ordered as an option or installed as an aftermarket item by a previous owner (PO).
On the chance you aren't sure what the rear sway bar looks like, here is an image of the rear sway bar I added (aftermarket) to my '71 CS convertible. Check the hardware is secure (if you have a rear sway bar). Again, check your shocks - I'm suspicious.
Reminds me of a sound I had when my frame rotted away in the back and my bumper was flopping around.
I'd suggest getting under the car and inspecting everything. Look at the frame, bushings, shock mounts, spring mounts, upper and lower control arm bushings etc.
Good luck.
Thank you everybody for the replies! I had a quick look today and there was indeed no rear sway bar installed.
I will have to take a better look sometime in the near future but I got some business trips to do before that.
I wish the issue is not extremely hard to solve as I do not reside in the U.S. and we have limited parts available here in the Nordics :-)
The rear noise still remains as a mystery as I have been very busy fixing everything else on this car, from doors to top hydraulic pump.
I think the car has not seen a proper maintenance at least in the last 20 years or more (including standing in a barn for a couple of years).
I also had a mechanic take a look and he fixed a case where brake pipe was rubbing on something badly. Now there are less noises but the main noise problem still remains.
I am going to order new front + rear springs and shocks (bilstein) from UMI Performance and ball joints + control arm bushings from rockauto.
The mechanic said that he noticed the suspension being very loose as he took it on a test drive, and as I know the suspension has been like this for AT LEAST 20 years, I think replacing everything at this point would be a good idea.
By searching the forums I found out all the MOOG rubber parts (K5196, K5149, K5161) and ball joints (K5108, K5103). UMI Performance sales recommended 1" drop front springs and factory height rear springs to keep the car balanced as I like it now.
If the problem is drive shaft rubbing floor pan, how can I fix it? Would it get fixed by replacing all the parts I mentioned above?
And yes, I can bounce the car.
Some folks either do or do not like a floor crawler - I like to use one (on concrete/asphalt). If your intention is to perform a fair amount of maintenance on the vehicle yourself over the next several years, consider buying a hydraulic floor jack and a minimum of four heavy duty jack stands so you can elevate the car. Then you have ample space to visualize everything & make life simple for yourself. You'll gain a far much better appreciation for what's actually going on with each component if you get the vehicle in the correct position to perform a safe working environment. BTW, use a flashlight - you can really get a good picture of undercarriage details with a flashlight. Shocks that old definitely need replacement.
As mentioned earlier, check the exhaust hangers. Grab the end of tailpipe and shake it. I had a bad hanger before the rear axle. Everything looked fine, but the pipe would rattle and I could pivot it from the rear.
Also check your UV joints, they connect the drive shaft at both ends to the trans yolk and the differential. Crawl under the car grab the driveshaft and try to turn it back and forth quickly. It will probably have a little play in it, but if it clunks, there probably bad.
And finally check that all the rear brake lines are securely fastened as appropriate.
Drive shaft rubbing floor pan, as it get worse when you have passengers ,
can you bounce the back of the car pushing down on it.
Mystery solved, this was the problem :-) Took a while to figure it out. There is now a temporary fix in place (lower rubber piece than the original one) until new springs and shocks arrive. Thanks everybody!
April 28th, 2023, 09:44 AM
Rear noise (e.g. potholes)
