Can anyone tell me why on the 05's 1500 4x4 (maybe other years) they call for 75-90 gear oil in the front axle and 75-140 in the rear? Would it hurt to use the same either or?
Curious why? I just purchased 2 bottles each Mobil 1 synthetic which went for 55.00

Thanks

 

Hello I was at the dealer the other day and they told me they just use 75-140 in both.

 

My guess is that 75W90 is all that is needed in the front diff since it's hardly ever engaged. Since it's always spinning, thinner lube might reduce drag ever so slightly and improve gas mileage a bit. I doubt anyone would ever notice the difference. However, be sure to use synthetic in the rear and don't forget the LSD additive. DC spec's syn in the rear while the front has no such claim.

 

Thanks for the response, It was really weird to see something like that out of the manual.

Mike

 

The heavier oil for the rear is mostly for towing. If you don't tow you could use the lighter oil in the back also.