I want to change the fluid in my dad's 96 3500 dually, but was woundering what kind of diff fluid you guys use. He tows at least 1-2 times a week and will have as much as 19000lbs behind him. I know that it calls for 80w90 but want something better. I was thinking 75w140 but then saw some 85w140 syn. from Royal Purple that looked pretty good. Have any of you tried it or what would you recomend? TIA


Cheers,
Adam

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99 DN 4X4 318-stock
07 JGC SRT8-P&P Heads and Intake, Headers, Off-road mids, Borla exhaust, Volant CAI, 180 T-Stat, CMR tuned 12.6 @ 107

75w140 synthetic is what I would use. 85w140 would be fine too but is a little thick for cold winters.

Make sure to add a bottle of friction modifier if the rear is limited slip. Some gear oils already have it so read the bottle of the stuff you choose. I wouldn't be too concerned about brand though.

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97 Ram Sport ext 4x4, 5.9L gas, 3" pro comp lift w dual shocks, 3:55 trac lock
Lt305/70R16 Kumho KL-78, K&N FIPK, Mopar Performance wires and cap, Stainless shorty headers, Walker exhaust. All syn lubes. Sirius sat radio! Magellan GPS
2003 Grand Caravan Sport. 3.3L No toys in it. Nobody's cool in a Minivan...