2nd Gen Non-Engine/Transmission Gear Oil

[Nate]

I'm pretty sure I did a thread on this a while back, but I can't seem to find it.



What gear oil viscosity are you guys using on your 2500s? My manual says SAE 90 was the factory fill.



I was running 75w140 synthetic, but I'm wondering if I should just go with 80w90?

 

[DiTrani]

Assuming you mean for the rear end, I think the wisdom is that you run 140 if you pull heavy a lot, and 90 if you don't, but if you're running synth, 140 is fine regardless.

 

[Nate]

Maybe I should have mentioned that I just put 4. 10s in the axles, so I'll be changing the oil soon after I break them in. I was running 75w140 with the old gears. I'm just wondering if 80w90 would be fine, as it's cheaper.



The heaviest thing I pull is my Jeep and trailer, which is about 7000lbs.

 

[Nate]

No one changes their diff oil??

 

[CumminsPower98]

I would say you are probably fine running 75w90 if not towing a lot. I ran that weight in Amsoil for a long time but now I'm towing most about 50/50 so I'm now running Amsoil 75w140. The stuff works out well as I have over 100k on the current fill and it still looks great.

 

[Nate]

The reason I ask is because the 75w140 is quite a bit more expensive than 80w90. I'll probably just run 80w90... I don't pull anything too heavy, just really the Jeep is about it.

 

[Nate]

Of the couple thousand people on this web board, only 2 or 3 have changed their diff oil??



Whatever I guess. I have a 5 gal pail of dino 80w90, I'll probably just run that since it's cheap. $100 for 8 quarts Amsoil, or $30 for 20 quarts of dino... hmmm.

 

[WBlackburn]

I have three Dodge pick-ups. A 92, A 2001 and a new one. On the older 92 with 387K on it, I have changed the diff oil at EACH 100k miles. Always use the 80=90 W oil. Works good for me, have never had a problem. I have 201K on the 01 and it tows a lot and seems to work ok.