I took my 06 in for the pinion seal recall last week. Elliot Motors in Davenport, Wa did the repair. I did not see any leakage on my garage floor although the rearend had some ring and pinion whine under both load and coast. When they inspected the rearend they found that the axle side seals were leaking also. They replaced 3 seals and the pinion yoke all under warrantee. The tech told me that GM says that slight gear whine is normal. The replaced the gear lube and installed the posi additive. I drove it a couple of hundred miles last weekend and found that after the rearend got warmed up the ring and pinion whine was worse that ever. I could hear it over the radio at speeds of 44 mph and up.
I went back to the dealer last Wednesday and told the tech about the increase in noise and requested that they replace the complete differential. Yesterday he called to report that he had talked GM into replacing the complete unit. So as soon as the parts come in I will take it back to him and get it changed. So far Elliot Motors has been great about doing what needs to be done. They didn't even dent the fenders. I will let you know how it turns out after the replacement.

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Mysterious with steel/sand and all options but Chrome wheels, Onstar and Smokers package.

That's the same scenario that ended up with my getting a new diff in 2006. It's been without a problem since then, but I had the pinions seal replaced under the recall last month, but everything is still tight as it should be, still no problems to report with the rear.

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"If you haven't seen the future, you haven't driven fast enough"
#000741, delivered 10/3/05

Got the diff replaced in my '06 last month. Started getting grinding noises during low speed turns after the recall work. It had the "clunk" since day one (a rather serious case, actually--everyone that rode in it commented on it). The dealership replaced it without a fuss.

No noise now, and no more clunk. Replacing the diff definitely did the trick.

Have your dealership check to be sure the new differential has the updated pinion seal in it. Mine didn't and I had to have the pinion seal replaced after less than 1k miles.

My rear end has been a lot noisier since replacing the seals on 22 May. Maybe I should have had them replace the Porpoises instead...

The differential came in. I will take the car in on Tuesday for the replacement. Hopefully is will be nice and quiet when I get it back.

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Mysterious with steel/sand and all options but Chrome wheels, Onstar and Smokers package.