Help! Rear axle/diff issue

[BadJudgement]

I was driving last night and I noticed what could only be described as a flat tire like feel. But there was no flat tire. I'm thinking something might be wrong in the differential or rear axle and wondering if anyone has had any experience with this? I've only put 500 miles on the car since I bought it with 45k miles and had the full service done at Cadillac immediately.

Any ideas before I start down a rabbit hole?

 

[Randy Lee]

Someone had mentioned that the wrong fluid was put in the differential from the factory. He suggested to change the fluid. I had a scrubbing noise and thought my tires were rubbing on the wheel well, especially when backing up. I have 42k miles. I have since changed the fluid and no more problems.