I am wanting to change my Differential fluid since I believe it has never been done with 105,000 miles on it. I was going to use Lucas 100% synthetic gear oil and wanted to know if anyone has dad issues with using this in the 1998 rear axles.

 

If you have an open diff then use 75-90w, 75-140w full synthetic for posi diffs.

 

I have a non limited slip diff that uses 80w90. However, just wanted to know if it would be better to use full synthetic. Also can you get paper gaskets for these diffs or only silicone

 

Not sure about the paper gasket, but I'd rather use a sealant personally.

As far as fluid is concerned, I use Mobil 1.