Rear End Oil Question

[DrL30047]

As soon as I can figure out how to change my Screen Name, in the future I'll be known as

[Edmac]

Don't know about what damage may have occured, but, if that 75w90 was not synthetic oil, you need to go get some more and do it again.
The reason I question this is that I don't think Wal-Mart sells synthetic differential oil here. If it is synthetic, you are probably in good shape.
Ed

[DrL30047]

It was Pennzoil 75w90 SYNTHETIC oil and cost $6.52/Quart. It was the only brand WalMart sold.

[Chevy2DMAX]

The owners manual mentions no requirement to change the grease. So, I guess that is what GM requires. Apparently, it is mentioned in a service manual somewhere. My last GM 3500 had a requirement of 50K miles. I don't think you have done any harm changing it at 10K. From what I read, it seems to suggest that the GM grease is the only product tested to minimize rear end noise.

[DrL30047]

Thanks for the replies so far, but does anyone know what would cause the oil to be chocolate brown? Does this indicate troubl ahead?

[AKDmax]

Water mixed with Diff oil is a cause of that. Not sure if it's your problem, but check your vent tube.