Diffy service

[mberry]

I will tell you that I'm running 75W-140 in my rear axle and when the temps were around 0 in the mornings my truck would almost stop itself without brakes. It would stop doing it after a few miles but it didn't make me feel any better about driving it. I am switching back to 75W-90 ASAP since I don't tow heavy and would like to get back some of my mpg during the cold winter days.

 

[Jason Hughes]

I have been using NEO synthetics. I was hooked when I needed to change the oil in my 5600 gear box due to very "notchy" shifting. I tried the NEO MTF and the transmission never felt better. It shifts smoother than it did when it was new and at 25K later still feels great. I now run the 10-40 motor oil in my CTD and it runs smoother also. Fuel mileage went up 1-2 mpg also. In the diffs I run the NEO RHD 75-90 gear oil and it works great. Can't feel the difference there but after frequent inspections the parts still look new. From what I understand many Indy car teams run this stuff. I have been very impressed to date. Just something else to consider.

 

[steved]

I will tell you that I'm running 75W-140 in my rear axle and when the temps were around 0 in the mornings my truck would almost stop itself without brakes. It would stop doing it after a few miles but it didn't make me feel any better about driving it. I am switching back to 75W-90 ASAP since I don't tow heavy and would like to get back some of my mpg during the cold winter days.

I'm running 85w140 in my rear axle and have no issues that you describe. It actually has increased my mileage and seems to have decreased operating temps of the rear diff. I currently have 108k on the truck, and 35k on the 85w140 with no visible wear metals on the magnet. I see temps from -25*F to 118*F with this truck driving cross country and it was one of the better fluid changes I have done with this truck.



Running the OE 75w90 and Mobile1 75w90 literally caused the paint to flake and bubble off the differential cover because it ran THAT hot. I actually drained what appeared to be burnt Mobile1 from the diff after 25k miles...



And from what I was told by a local dodge tech, (his dealer also recommends 75w140 for the AAM when towing) that the 75w90 spec was actually to increase fuel mileage, not prevent wear. So take that for the gossip it is...



I am not telling anyone what to do with their truck, just telling you what I have experienced.



steved