Best synthetic transmission oil

[Diesel_Dave]

I'm considering switching my transmission fluid oil to synthetic. I know a few folks here have done it. What brand/type do you think is the best? Anybody done any testing or have a link to any data?

I'm also looking at switching my rear axle oil to synthetic as well.

[Phantom]

I believe the axle fluid is currently synthetic according to Dodge Ram Fluid capacity and specification Information

[Diesel_Dave]

Well, I bought the truck used with 70k miles on it. I have no way of knowing what fluid is in it. Secondly, I see from that link that a certain synthetic fuid is recommended for "Axles intended for heavy-duty or trailer tow", but I don't have any way of knowing whether they considered my truck that way when it was built.

[DonR]

Personally I prefer Red Line. No testing, just because.

I use the stuff recommended for the application.