So, research isn't leading me to any exact answer. Does the ptu and the rdu both need friction modifier? When I changed my ptu fluid I just used royal purple with the friction modifier already in it. Going to do rdu soon and want to know if i need modifier. I read from some people that the ptu has clutch packs, but also saw someone mention it doesn't have any clutches and only the rear has the clutch. Just want to figure it out as reading for over an hour hasn't helped Ha. Thanks everyone!
No friction modifier needed. BTW, the RDU holds what, over 3x the amount of fluid that the PTU does? RARELY hear of any issues there. So just use a quality full synthetic gear oil, and don't worry about it. I'd like to say a fluid change interval of 50K miles is good for the RDU, or at least a check every time you change the PTU fluid.
Quote from: SHOdded on March 16, 2015, 05:27:53 AM
BTW, the RDU holds what, over 3x the amount of fluid that the PTU does?
PTU gets 1.1 pints of 75-140
Rear Diff gets 2.3 pints of 75-90
So not quite 3x the amount.
I change out both fluids religiously, once in the Spring, once in the Fall, regardless of mileage accrued.
I too use Royal Purple exclusively as well. Seems to have paid off thus far.
Knock on wood, no issues to speak of, after 5yrs, and 63K on the clock.