KamaSutra

punishmentcycle, you were right from the start.

After a brutal Chicago winter and no time to look into this further until now, I can officially confirm that the noise I'm hearing is gear backlash from the differential. I was finally able to get the car up in the air and record it while a buddy was clutching in and out. Some of the noise does resonate through the aluminum driveshaft but its all coming from inside the differential.

So just as mentioned earlier in the thread, I never really needed a differential in the the first place as my old one did the same thing. Only thing cured was the typical whine that develops over time.

Video:

If you're on the mend between stock differential (4th gen, 3rd gen, etc) and a 8.8/9 inch swap. Go for the latter if your budget allows. Do not waste your time with stock junk. The Getrag differential for the CTS-V1 is a certified piece of dog **** and should be recalled like everything else GM is owning up to within the past 10 years.

The only thing I'm left to wonder is if anyone has ever tried to adjust the backlash.

05CTSV

iTrader: (16)

I had an old diff that tore completely apart, it all comes apart easy enough. I never put it back together though...LOL. I'd think you would be able to take off the side cover and pull the bearing from the carrier on the ring side. Put a shim of some thickness under the bearing and press the bearing back on. Put the carrier back in, torque down the case bolts and see if the back lash improved. That's the only way I see of moving the ring closer to the pinion.

Stone17

iTrader: (3)

All that work and you still have the clunking. Sound like a bowling alley.

Have you look at the clutch yet?

Get a stethoscope. Get the car back on a rack and listen for noise around the bell housing and transmission.

With the car on the rack. Hit the brake, and put the car in first gear and release the clutch (don't let the car die). Does it sound the same?



Try and get a inspection camera inside the bell housing too.
Attached a picture of where to put the camera in.

bmylez

iTrader: (3)

^^^ He has a Diamond stg 2 clutch so I would say definitely not the problem. It is 100% the diff and mine does the same thing. I have a stock diff in an '07, which makes it a 3rd gen. I thought CS bushing/block and motor mounts would help, but nope. I am actually very curious if there is anything that can be done to take the slop out of the diff internals. Part of me wants to get an unwanted diff from someone, crack it open, have a shop spec all tolerances/torque, replace all fasteners with higher quality, and shim gears if necessary. Probably more effort than it's worth, but from all the diff failures I've seen, the gears don't shred apart, it's the case. Surely something can be changed out to help prevent this.

NIKDSC5

iTrader: (10)

My opinion, in that video that is excess slack in the diff reverberating back through that 1 piece aluminum drive shaft. Sounds like an old truck with the same problem. Since the power is coming in waves it sounds worse, as any slack in the trans is going to amplify it as well. In the video you should lightly apply the parking break and simulate a start and stop scenario to ID a diff clunk. Or just hold the brake with the trans in neutral and rotate the drive shaft to see how much slop there really is. I'm guessing a bunch. Is that car cammed? I'm just curious because it would make a great video to demonstrate what cam bucking is.

bmylez

iTrader: (3)

Looking at his mods, I'm going to say stock cam.

KamaSutra

While it wasn't on the video, we also did a start & stop scenario and even ran though the gears like normal. The clunk is more noticeable when clutching in and out quickly, shifting into 5th, or engaging a fast downshift. We also went at it with a stethoscope, its all coming from the differential. You can feel the engagement when putting your hand underneath the differential while clutching in and out. All of the stock parts that are commonly considered by majority of V1 owners to be the cause of the clunk were replaced.

jfensty

iTrader: (1)

Has anyone tried to shim out some of the play that is built into the diff from the factory? Seems like you should be able to lessen the amount of backlash between the ring and pinion.

KamaSutra

This is what I want to know, its about the only way this issue can be reduced. I'm going to ask around locally and see if I can find any shops that can advise.