[lively]

When I drive the car hard, I get a loud thunk from the back of the car on the 1-2 shift. After looking under the car, while doing the skip shift eliminator, I noticed the differential is bolted up in the front, but rides in a rubber insulated bracket in the rear. Just wondering if any of our Aussie buddies can confirm this sound, and is there a fix, such as poly insulated bracket?

 

[ChimChim]

When I drive the car hard, I get a loud thunk from the back of the car on the 1-2 shift. After looking under the car, while doing the skip shift eliminator, I noticed the differential is bolted up in the front, but rides in a rubber insulated bracket in the rear. Just wondering if any of our Aussie buddies can confirm this sound, and is there a fix, such as poly insulated bracket?

That noise is annoying as hell, there has to be a way to fix it..........

 

[CMNTMXR57]

Yea, I've repeatedly posted about this. It's the slack in the rear halfshafts.

 

[Howie]

Yea, I've repeatedly posted about this. It's the slack in the rear halfshafts.

Noticed the same thing, whats the solution?

 

[lively]

I don't think it's the halfshafts myself, it seems more like something is hitting the body. That's why I think it's the diff mount.

 

[CMNTMXR57]

I dunno what the solution is yet. I'm begining to wonder if the pinion/nose on the differential may be smacking the floor as there is no way to control it without a torque arm or similar device.

 

[lively]

It looks like the nose is mounted to the body,and the rear of the diff is allowed to move in the bracket. That's why I think it is bottoming out the insolator in the bracket.

 

[CMNTMXR57]

I wonder if there is a way to "hold" it?

 

[lively]

Looks like a good place for a poly bushing to me, but I'm not an engineer.
Hey mixer, check your PM.

 

[Diggs]

Sheeeesh...

And I thought I had broken my new car.

I hit it hard today and it sounded like the rear end was coming out of it. At least this thread let me know it's not just me, even if we don't have a solution yet.

Diggs

 

[JimHoward]

Hmm. I thought that it was the wheel chocks. I haven't taken them out yet.

Sure hope we get to the bottom of this one. It really is annoying and may possibly be damaging to something.

Jim

 

[cvp33]

Same thing in the CTS-V. Bronko and I flogged it tonight. Heavy thumping in 1st gear launch, then again at 2nd shift and then again in 3rd. Annoying.

 

[mistermike]

OK, Who volunteers to get under the car with a creeper and camcorder while I bang some gears?

 

[Holeshot]

OK, Who volunteers to get under the car with a creeper and camcorder while I bang some gears?

:slap: I will :slap: :drink: :drink:

 

[GTOJer]

Actually, my electrical bud has a battery powered camera and we plan on doing just that. We both want to see what is going on back there. Don't worry, it will get posted....

 

[mistermike]

Actually, my electrical bud has a battery powered camera and we plan on doing just that. We both want to see what is going on back there. Don't worry, it will get posted....

Great idea! I still like the human factor though. With Holeshot as camera man, we could get Tails to be the anasthesiologist. :drink: :drink: :drink:

 

[cvp33]

Just duct tape him to the exhaust.

 

[Tails]

Trust me...Duct Tape works great. I have the scars to prove it!!
:drink: :drink:

 

[USA ZR-1]

The differential forms the rear portion and aft mounting point of the rear cradle/suspension sub-frame. The whole assembly is carried in a three point rubber mounting arrangement. I'm beginning to think the clunk occurs as the rear cradle/diff assy. "unwinds" just AFTER the shock-load and the rear diff rubber mount "tops out" against the top of the mount cage. There is a witness mark in that spot. One thing for sure, this has to be fixed, it makes a great car sound awful.

 

[USA ZR-1]

Effective fix for thunk from diff mounting

I installed the parts to fix the diff mounting clunk we've been discussing. It works! It eliminates the banging sound when you do a hard 1 to 2 shift or otherwise "dump" the clutch. Of course it does nothing for the wheel hop but I think the cure for that may be in the same area, i.e. to limit how much the rear cradle is allowed to move around on a shock loading of the driveline. I doubt GM will be addressing the wheel hop which happens when abusing the car. The fix for the clank/clunk is put two part # 90447991 cushions between the front right side cradle mount and the floor. You need to modify the cushions to allow both pieces to fit on the mount boss but this is very simple. For those who want the dealer to do the work, they will need to contact TAC for instructions. The VIN range of your car may be a factor since later cars may have the bushings from the factory. Mine was built 11/03 and it had no extra bushings on the right side rear cradle mount. I'll post again if I get rid of the wheel hop. Would be nice, the ZR-1 does not have that problem.