rear end knock
Thread Starter
5th Gear
Joined: Nov 2017
Posts: 5
Likes: 0
rear end knock
I took my 2011 Grand Sport to a local dealer for an oil change and to get the filter in the transmission replaced. I bought the car with 24K and took it in for service at 28K. Nothing was wrong, I just wanted a good known starting point for future service. When I got the Corvette back, it has a knock in the rear end now. Sometimes it is not apparent and sometimes is sounds like a flat tire...I pulled over to check the tire once. I am not sure what could have went wrong just dropping the pan and changing the filter in the transmission. I have taken it back to the dealer and the shop foreman told me it sounds normal to him, but it wasn't doing it like before. It mainly does the knocking under a load, like accelerating up a hill. It doesn't have to be a hard acceleration either, just drop a gear or two and it would start knocking. It sounds like a repetitious knocking when it does act up. Does anyone have an idea as to what might have caused this?
Team Owner
Joined: Sep 2005
Posts: 20,352
Likes: 568
From: Ventura County, Calif
It's tough to diagnose noises over the internet. What you describe doesn't sound familiar but you may not be describing it correctly, in which case it could be several things.
Is it possible for you to get an audio recording, post to youtube and link it here? I think that's the only way we'll be able to offer solid help.
Is it possible for you to get an audio recording, post to youtube and link it here? I think that's the only way we'll be able to offer solid help.
Thread Starter
5th Gear
Joined: Nov 2017
Posts: 5
Likes: 0
I don’t have anything to record with except my phone and that didn’t work. I bought a set of steelman chassis ears and hooked one up to the plug on the transmission pan and the other to the cooling fins of the rear differential. Also hooked one to each exhaust and I couldn’t locate the knock. Of course, I’m not a mechanic. I get a high pitch whine from the transmission and a lower pitch whine from the differential. Feels like when torque is applied something starts popping. I can feel it in the gas peddle and the floor board. Is there a better way to use the chassis ears?
Instructor
Joined: Mar 2016
Posts: 149
Likes: 24
From: Ross Ohio
Check for loose axle nuts...it's a well known/discussed issue and very easy and cheap to fix. I had what I would call a clunking noise in the rear under certain conditions and these were the fix. Pop the center cap off the rear wheels and the axle nut is right there; no need to remove the wheel or anything.
Last edited by jkirk1; Nov 13, 2017 at 01:33 PM.
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Thread Starter
5th Gear
Joined: Nov 2017
Posts: 5
Likes: 0
Someone local suggested taking it to Straight Line Transmissions. Caleb at Straight Line checked it out today and said he found the muffle hitting the frame and was almost absolutely sure that was the problem. I picked it up from him this afternoon and I have not been able to duplicate the problem after driving 50 miles. Huge thanks to Caleb at Straight Line and much appreciation to everyone here for all the suggestions.