I was just wondering what the best type of rear gear oil to use cause i am about to change mine. Is synthetic the best way to go or not. Also what is the best brand?

 

I've always like Redline (I used the 75w90) in the drivetrain and Mobil 1 in the powertrain. Other than my tranny my truck is 100% synthetic.

 

I've always like Redline (I used the 75w90) in the drivetrain

thanks for the info, but i was reading in my manual and it said to use 80w90.
does that make a difference or is it just a recommendation from DC?. how often do you need to change it? and thanks again.

 

Don't know if it's the best but Royal Purple works for me.
Here's a recent topic in the 24 valve forum that asks the same question
https://www.dieseltruckresource.com/...threadid=75677

 

I'm not sure what the offical period is but I'd go with about 20k if you tow a lot or 40k if not.