Car is in sig. Approx 48K miles. Regular oil changes performed at 7500.

This car is used as a grocery getter. We bought it new, so I know it's history. Lately a strange knocking noise has developed when under acceleration. It doesn't seem RPM related, more like speed related. Lift off the throttle and it goes away. I'm not getting any feedback through the steering wheel, so it doesn't seem suspension related. It's hard to tell, but it's almost the same noise the engine air system makes right after the engine is started. I can't remember what that part of the emissions system is called. Are there any common problems which fit this description. Had the power steering recall done and this seemed to surface soon(but not immediately) afterwards.

Thanks for any insight,
Billy

Maybe an exhaust leak any codes

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Might just be spark knock from bad gas too.... If you could better describe the sound....

An exhaust leak, or spark knock should vary with RPM. This noise doesn't, so I've kinda ruled out engine. We've run a few tanks of premium to rule out the fuel issue also.

I have a ScanGuageII I can hook up. I don't know how well it'll read this car. I have no CEL's.

Thanks for the quick reply.

Does it vary proportionately with speed?

---------- Post added at 09:43 PM ---------- Previous post was at 09:42 PM ----------

Doubt you'll get a code from a noise!!!

I would like to look into this for you. If you would like my help could you please message me your VIN, current mileage and full name?

Jackie
Chevrolet Customer Care

Well, at 42,200 the noise I was hearing is coming from the final drive. The car needs a new transmission already.NOT COOL!

---------- Post added at 10:44 AM ---------- Previous post was at 10:31 AM ----------

I tried to PM you Cust Svc, but I don't have enough posts. Car is at Findlay Chevrolet in Las Vegas, NV. Billy Chang is service writer. This is unacceptable.

Video of the sound?

It's torn down at the dealership now. Last drive I took it only made the noise under acceleration. Sounds like a card in the spokes of a bicycle wheel. Loud clicks, almost knocking, is the best way to describe it. Its getting taken care of.

I've had that sound before but on a different car. It was the engine mount in the back against the firewall. When I would step on it the engine and transmission would tilt back too far and lower the drive axles and the damper on the axle would rub on the serpentine tensionner. It took me a long time to find it until one day it was on the hoist and I saw the shinny spot on idler where damper was rubbing.

Sad to hear about your tranny.