Both rear axle seals failed and leaking by 27,000 miles is not acceptable. I purchased the car used 5/17. After owning the car for a few months, I began hearing a groaning noise from the differential every time I had the car in reverse. It became worse when turning the car while backing up, particularly to the left. It lessened some after the car was warmed up. I took the car in to the local Cadillac dealer, Capitol Auto Group, in Salem, OR, was told they could not replicate the problem, that it was probably just the positraction unit, and let them know if it continued. The noise worsened over the next 6 months and through the warm summer months, so I took it in again, only to be given the same response. Once more, I took it in in 12/18 on another issue and complained about the noise. This time I was told "It's normal. Even some Corvettes and Camaros have it. Don't worry about it. The tech checked it out and couldn't find anything." I was even given an official GM print out, #09-04-20-001F (tire chatter vs. rear differential chatter),as the advisor tried to convince me that it was nothing. I wasn't buying it. I've been driving and working on cars for 52 years. I know cars and have had several with positraction rear ends. I've never had one make so much noise. It was audible from outside the car.

Upon searching in an on-line Cadillac forum, I learned that premature failure and leaking rear axle seals was somethings other had experienced resulting in low lube levels and A GROANING NOISE FROM THE DIFFERENTIAL WHILE IN REVERSE. Others mentioned a change in fluid made the noise go away. I decided that I would foot the bill to swap out the fluid to the tune of $135. I made the appointment less than two weeks after I was told there was nothing wrong and that the tech could find nothing, took the car in to have the fluid changed, and was told that the tech had now found that both rear axle seals were leaking and needed to be replaced. This was 2 weeks after I was told that there was nothing wrong. Give me a break. Whoever checked the car, missed it. Fortunately, it was covered by the powertrain warranty. Axle seals failing at this low mileage causes me great concern about the longevity of the part. I also worry about damage to the differential. Will they fail again in another 27,000 miles? I have to wonder. And of course, it will be out of warranty on time by then.