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Discussion Starter #1
I need some help guys because I am out of ideas. I have a 2010 Cobalt ls that I am fixing for my elderly mother. There is a thumping noise when I turn the wheel and accelerate slow when backing up. The thump noise seems like it is under or near the driver side. I replaced both lower control arms with balljoints, the stabilizer links on both sides and the stabilizer bar bushings that mount to the frame, the rear coil springs which were broken, and a leaky driver side axle. The tie rod ends have no play and the wheel has no play. All of the parts are new and manufactured by moog. What other part or parts could be the source of this problem? I am completely baffled by this one and fast response is appreciated so I can repair and return her car safely.

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bizzs
 

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Any play in the steering column? Maybe intermediate shaft.
 

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Discussion Starter #3
Thanks for the response. There does not appear to be play in the steering wheel or shaft. The thumping sound is not on a constant basis. The sound seems to be near the driver side floor like something hits the floor. I thought it was the stabilizer bar hitting the frame or floor so I replaced both links and bushings with moog products. That did not solve the problem so I changed both control arms (moog) with ball joints and the thump still occurs. The noise occurs when I back up slowly and turn the steering wheel slightly to the right at a certain spot. It happens quickly and it's hard to diagnose. The best way that I can describe the sound is if I was to knock on the floor once. Any Ideas ?

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bizzs
 

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I would still check the lower universal joint of the intermediate shaft. It is exposed to the elements and often fails.
 

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Discussion Starter #5
I had the car up on my buddies rack today. We wiggled the steering wheel without the motor running and there seems to be a noise from the rick and pinion. Is it common for the rack in pinion to malfunction with 27,000 miles on it? The universal joints at the steering do not appear to have any play in it. I have read many articles on this but I am not sure which part to start with. I have about 300 tied up with this repair so far and my guessing is getting costly Any recommendations?
 

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Could be an inner tie rod but 27000 miles is low miles. Although all you really need to destroy a component is a good pothole. Did you check the bolts holding the rack to make sure they were snug? What about the 3 nuts holding each upper strut? My 08 I replace almost everything in the front end for a similar noise. Ended up being a lower driver's door hinge that had play, go figure, but it sure sounded like something was hitting the floor.
 

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Discussion Starter #7
I pulled the 60amp fuse out and I can hear a clicking thumping noise when I do fast movements side to side with the steering wheel. When I turn the steering wheel full left and right turns, I do not hear the thumping. When I back up and start to turn the steering wheel, the thumping sound is more noticeable with the fuse removed. Does this sound like the rack is bad? The car steers fine when driving and there are no problems when making 90 degree turns. The shaft universal is not binding nor does it feel like it has play. From listening and feeling, the noise seems like it is in the rack and the sound waves of the thump is being distributed through the suspension. Any thoughts? Can anybody recommend a economical rack replacement that is the bang for the buck?

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Check those sway bar bushings again and verify you got the correct size.
27k miles seems quite low for a tierod to go...but gump happens.
As for complete rack with inner tie rods ~$150-250 with a $100 core for a reman to about $250 outright for ACDelco new form RockAuto
New rod ends are around $10 each for the outters and $20 for the inners.....some are less expencive than others. YMMV

Then youncan go to gmpartsxxxx dot com and check any of many gm parts listed on line.
Mind you, weather you install the rack or just rod ends, schedule a toe-in adjustment from your local friendly alignment shop.....or ger really good with a tape measure.

BTW. Did the same repairs on my 08 LS and it turned out to need those sway bar bushings for the noise.
 

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Discussion Starter #9
I still cannot find a solution to this problem. I had the car state inspected today and it passed with flying colors. I can still hear that knocking-thumping sound. The steering shaft feels and looks tight. The struts look good, they are tight, and there is no oil leaks visible. I verified that the sway bar bushing were the correct ones with the dealership. Could this be the rack and pinion? When I turn the wheel, without the motor running, back and forth quickly, there is a clicking noise. There is no clicking noise when the motor is running. Thoughts anyone?
 

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Did you check the halfshafts/CVs?
 

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Discussion Starter #11
Yes I did replace a shaft because because the boot was ripped. The sound is not a clicking sound like many have posted on the net regarding the steering shaft. There is no vibration in the steering itself or clicking when turning side to side when the motor is running. It is more of a random thud sound that happens when I back up and turn the wheel a certain way. The sound seems like it is under the driver side and it is a hard one to diagnose because it happens quickly. Thoughts?
 
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