I understand the nasty clunking noise when shifting 1st and 2nd is "normal" but it drives be crazy. Anybody tried the pinon support brace by BMR to correct this? Thanks

Can you post a link to this brace? The clunking bothers me as well but I didn't know there was a fix for it.

I would think a pinion brace would be more for anti-wheel hop.

Matt has this on his car, and the car STILL clunks. There is major play in the driveshaft (not front to back play, but rotational play) inside the diff. It is especially prevalent in stop and go (1st gear) type scenarios.

The support brace can be found at: http://www.bmrfabrication.com/. The description makes sense since it apparently utilizes a sitffer bushing to take up the rotational play.
I am struglling to understand how this can be normal - it's embarrasing when showing off the car.

I understand the nasty clunking noise when shifting 1st and 2nd is "normal" but it drives be crazy.

Wow, is that what that is? I always think something in the trunk has come alive and moved around, or I run over something virtually standing still!

The support brace can be found at: http://www.bmrfabrication.com/. The description makes sense since it apparently utilizes a sitffer bushing to take up the rotational play.
I am struglling to understand how this can be normal - it's embarrasing when showing off the car.


Have you seen any install instructions for this piece? I might consider picking one of these up and trying it out. 4° of movement is a lot.

Here's the installation instructions....There is a pic too but it makes the file too large to attach. The picture is the same as is on the BMR site.

BMR
PINION SUPPORT BRACE CTS-V
Part # PSB001

NOTE: Although this installation can be performed with a hydraulic jack and stands, a 4 post service lift is recommended.
1. Lift vehicle and support.
2. Remove the lower four pinion support bolts on the differential (See Image 1 below).
3. Using a floor jack, support the differential.
4. Loosen and remove the front differential mounting bolt located above the driveshaft on the passenger side. It may be necessary to lift or lower the jack to release the tension from the bolt in order to slide it out of the differential and cradle.
5. Slide the new 14mm bolt through the BMR pinion support and position it onto the differential as shown in the image below. The provided bolt should slide through the BMR pinion support, through the rear cradle, capturing the differential. Again, it may be necessary to use the jack to lift or lower the differential in order to get the bolt through the mounting points.
6. Insert the four new bolts into the differential and tighten to 25 ft/lbs. Use the factory nut on the main differential bolt and tighten. It is not possible to use a torque wrench in this area but make this connection as tight as possible. The new provided bolt is Grade 10.9 and will handle up to 170 ft/lbs.
7. Lower vehicle.

The clunking is more like tranny slack being taken up. No fixe and won't be one.

Thanks for your thoughts Ames, but I don't beleve it's tranny slack - GM's service bulletin info states the noise is from the front and rear drive shaft rubber isolation flanges, center drive shaft support and axle backlash resulting in the noise caused by torque reversal. It sounds like the car is going to fall apart sometimes.

For anyone following along with this clunking in the shifting - I have GM looking into the support brace option. The information has been sent to them.
In the mean time, I suggest anyone else experiencing this probelm go GM's website, select "contact us" and complain about it. Perhaps we'll get it corrected.