Anyone know who makes the 75W-140 synthetic gear oil that Mopar uses? Anyone running it? I have a friend in the dealership that can get me all I want for free. Is it worth it? I'll be changing it tomorrow night unless someone persuades me otherwise.

Thanks.

 

It is made by mobil....free is a good deal. I will take 5 quarts and pay shipping...ha.

 

75-140 is called for in the 1500 trucks, the 2500, 3500 have a different syn fluid, 75-90 or something like that. I'll try to get specifics on that today.

 

Yeah, I saw that in my owners manual. Is it going to make that much of a difference? Do the bigger rears need a thinner oil or something?

Thanks.

 

The Dodge owner's manual recommends 75W-90 for light loads and 75W-140 synthetic for heavy towing for the Dana axles in the 2500 and 3500. Since cold temperatures aren't a problem here on the Texas Gulf Coast, I run Royal Purple 85W-140 synthetic to tow our 13,500 lb 5th wheel. It works great - no supplemental friction modifier was required for my truck's limited slip (it's blended into the RP formulation). YMMV.

Rusty

 

I was looking a RP or Redline, but free is better IF it's a good product. I'd rather pay than put free junk in.

 

I dunno who makes it, but I ran the Mopar 75W-140 synthetic in my 1996 3500 that was used to tow 5th wheels. It worked just fine.

Rusty

 

OK, I did a little scientific testing. I took a bottle of 80W-90 dino gear oil, a bottle of the Mopar 75W-140 synthetic and just for kicks, a bottle of Redline MT-90 and put them in the fridge for 24 hrs. I did the scientific pour method this morning. The dino oil was like honey, the Mopar was slightly thicker than room temp, but def more pourable and the Redline was slightly thinner yet.

What does it prove? Do the testing when your wife isn't home!!! What is it with women and putting gear oil in the fridge??

 

The only thing they hate worse is putting motorcycle engine casings in the oven to heat them up so that you can drop bearing races into them.

Rusty

 

Or powdercoating, that stuff stinks.

 

FYI, the Redline MT-90 you experimented with is not intended for use in truck differentials. It's a GL-4 transmission lube oil formulated for synchronizers, with some GL-5 properties. It's similar to Redline MTL, but formulated with higher viscosity.

Redline makes a synthetic 75W-140 GL-5 gear oil compatible with differentials that is of the same or slightly better quality than Mobil.

 

Yeah I know. I just did it to see how it would pour cold. Thanks for caring, man(wipe tear from eye)

 

IMHO, you can't go wrong using the OEM oil especially if it is free.
Wish I could get it for that price.