Advice about a thump in the rear? - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

pnwdan · 06-12-2020, 10:02 PM

2014 SS M6 car.
Car has 56k on it.
12k on a cam, tune and fresh and super quiet 3.91 gear install.

Here is the back story.
Was aggressively cruising on the freeway a couple weeks ago and downshifted to pass someone and blew up the right CV. Towed it home and replaced with an OEM GM shaft a few days later.

All was well for a week and even put the car through a 250 mile round trip but now the car seems to have developed a thump in the back.

I have NPP and the car is cammed so I usually have the exhaust set to stay open. Since the CV incident, I have been paying abnormally close attention and closing the exhaust. I have no idea if this thump is new or something it has been doing for a while that I didn't notice.

When low rpm cruising i can let off the gas and then press it gently and i get the thump as if it is when the drivetrain is loaded with torque on it.

If I back up, pause, then pull forward I get it too but not always.

It sounds like something hitting the floor in the back... A low key thud.

I plan on trying to get under the car tomorrow but my sons car is apart in my garage (its a BMW nightmare) so i have to do it in my driveway and the neighborhood frowns on that ha ha. I would like some pointers before i go digging around so i can try and limit the time the car looks like its being parted out in my driveway.

As always, I appreciate all the help

Vegas Bound · 06-12-2020, 10:56 PM

Carrier bearing.

pnwdan · 06-13-2020, 12:03 AM

Quote:

Originally Posted by Vegas Bound

Carrier bearing.

I am assuming you mean in the diff?

Had the wife stand behind the car and beside the car. She said from behind the sound is coming from just left of center and from the side its aligned with the wheels. No growling, whirring or anything else though.

'10CamaroDude · 06-13-2020, 01:58 AM

Just saw a U-Tube video that said his thump was the rear LCA. Also shows it
was mangled... Check suspension parts.

pnwdan · 06-13-2020, 12:53 PM

I checked all the suspension. Only things I have found was right rear coilover was loose and sway bar end links were not torques to spec. Fixed both of these and it still does it. I can reproduce it 100% of the time by reversing slowly, shifting into 1st and slowly letting out the clutch. With the window open it is a very loud and pronounced bang with a thud on the car and a metal twang. Its like something is shifting in the drive train.

It sounds like it is on the left side of the car. Can hear it really clear sticking my head out the window and reproducing it.

what kind of play should be in the axles going into the diff?

Has anyone heard a CV do this ?

pnwdan · 06-13-2020, 01:38 PM

Well here is a comical update.

The diff was loose. Not really loose as in you can push it around by hand or even with a short pry bar but the rear mount was loose enough that the diff could rock up and down under torque a bit. The metal ping sound was the bold hitting the opening.

Weird for sure as they are self locking nuts and I have so many miles on it since the diff was rebuilt.

OEM spec is 59ft/Lbs. I added some blue loctite and a bit more torque.

Also decided while i was under there that i will take this summer to replace all the soft bushings everywhere with better ones including the diff.

christianchevell · 06-13-2020, 04:19 PM

You should also get some BMR toes and trailing arms for loss of wheel hop while your under there and if you ever do sways get metal end links the stock plastic crap is just that...Good Luck

pnwdan · 06-13-2020, 04:34 PM

Quote:

Originally Posted by christianchevell

You should also get some BMR toes and trailing arms for loss of wheel hop while your under there and if you ever do sways get metal end links the stock plastic crap is just that...Good Luck

Good advice thank you

06-12-2020, 10:02 PM	#1
pnwdan Drives: 2014 2SS/RS Join Date: Jan 2018 Location: Washington Posts: 848	Advice about a thump in the rear? 2014 SS M6 car. Car has 56k on it. 12k on a cam, tune and fresh and super quiet 3.91 gear install. Here is the back story. Was aggressively cruising on the freeway a couple weeks ago and downshifted to pass someone and blew up the right CV. Towed it home and replaced with an OEM GM shaft a few days later. All was well for a week and even put the car through a 250 mile round trip but now the car seems to have developed a thump in the back. I have NPP and the car is cammed so I usually have the exhaust set to stay open. Since the CV incident, I have been paying abnormally close attention and closing the exhaust. I have no idea if this thump is new or something it has been doing for a while that I didn't notice. When low rpm cruising i can let off the gas and then press it gently and i get the thump as if it is when the drivetrain is loaded with torque on it. If I back up, pause, then pull forward I get it too but not always. It sounds like something hitting the floor in the back... A low key thud. I plan on trying to get under the car tomorrow but my sons car is apart in my garage (its a BMW nightmare) so i have to do it in my driveway and the neighborhood frowns on that ha ha. I would like some pointers before i go digging around so i can try and limit the time the car looks like its being parted out in my driveway. As always, I appreciate all the help __________________ 2014 2SS/RS LS3/M6

06-13-2020, 12:53 PM	#5
pnwdan Drives: 2014 2SS/RS Join Date: Jan 2018 Location: Washington Posts: 848	I checked all the suspension. Only things I have found was right rear coilover was loose and sway bar end links were not torques to spec. Fixed both of these and it still does it. I can reproduce it 100% of the time by reversing slowly, shifting into 1st and slowly letting out the clutch. With the window open it is a very loud and pronounced bang with a thud on the car and a metal twang. Its like something is shifting in the drive train. It sounds like it is on the left side of the car. Can hear it really clear sticking my head out the window and reproducing it. what kind of play should be in the axles going into the diff? Has anyone heard a CV do this ? __________________ 2014 2SS/RS LS3/M6

06-13-2020, 01:38 PM	#6
pnwdan Drives: 2014 2SS/RS Join Date: Jan 2018 Location: Washington Posts: 848	Well here is a comical update. The diff was loose. Not really loose as in you can push it around by hand or even with a short pry bar but the rear mount was loose enough that the diff could rock up and down under torque a bit. The metal ping sound was the bold hitting the opening. Weird for sure as they are self locking nuts and I have so many miles on it since the diff was rebuilt. OEM spec is 59ft/Lbs. I added some blue loctite and a bit more torque. Also decided while i was under there that i will take this summer to replace all the soft bushings everywhere with better ones including the diff. __________________ 2014 2SS/RS LS3/M6

06-13-2020, 04:19 PM	#7
christianchevell old school chevy rodder Drives: 2013 2SS/RS Manual,DM exhaust,CRT Join Date: Jul 2012 Location: Oregon Posts: 5,587 View My Garage	You should also get some BMR toes and trailing arms for loss of wheel hop while your under there and if you ever do sways get metal end links the stock plastic crap is just that...Good Luck __________________ 2021 Wild Cherry ZL1 A10, Sunroof, Data, Carbon, Nav, RotoFab Dry CAI, Elite x2, Borla ATK, Driveshaft shop

06-12-2020, 10:56 PM	#2
Vegas Bound Account Suspended Drives: 2013 Sparkly Red One Join Date: Dec 2018 Location: Hospitality State Posts: 2,558	Carrier bearing.

06-13-2020, 01:58 AM	#4
'10CamaroDude Account Suspended Drives: 2010 Camaro LS Join Date: Nov 2019 Location: Pgh Posts: 739 View My Garage	Just saw a U-Tube video that said his thump was the rear LCA. Also shows it was mangled... Check suspension parts.