4RGSP

Having the fluids changed out on my truck.
The dealer is saying that they should put in SAE 90 Gear lube and I told them that I wanted to use a synthetic per chrysler. Isn't there a TSB regarding synthetic for towing???

RustyJC

It's in my owner's manual under the either the trailer towing or the lubricant specification sections. Although I don't have the truck here at work to cite page numbers, it was in the manual for my 1996 3500 as well.

The Dana 80s come from the factory with 75W-90 dino, but my manual recommends 75W-140 synthetic for heavy trailer towing. Personally, I went with Royal Purple synthetic 85W-140 since we tow HEAVY and low temperatures aren't a problem here on the Texas Gulf Coast. The RP synthetic already has the friction modifier blended in for the limited slip differential - mine didn't require any more friction modifier than what was in the RP hypoid gear lube, but these limited slip differentials vary a lot from one truck to another, so YMMV!

Rusty

Hemi Cat

80-90 is fine but the synthetics are the best. If it is a limited slip, make sure you use the limited slip oil and add the additive too.

RustyJC

Careful here. If you use an oil that already has the friction modifier blended in, drive the truck before you add any more friction modifier. You want just enough friction modifier to keep the LSD from chattering on corners. If you arbitrarily dump in too much friction modifier, you'll find your limited slip differential no longer has any limits on its slip (i.e., it no workee any more!)

Rusty

hoser

75-140 SYNTHETIC....$$$$ is a great year round hd oil

4RGSP

Now I have to convince the dealer they screwed up. $$$

hoser

no , you just have to change it sooner

infidel

Not necessarily. If you're towing during the winter or keeping to the north towing in summer the 75W-90 will be fine. I know a lot of people who live in the north don't like 75W-140 in the winter, you can actually feel the extra thickness drag you down while coasting in the cold. Assume the same drag must be there when you're not coasting, you just can't feel it.

4RGSP

They put in straight SAE 90, not 75W-90. The Dana 80 rear ends recommends the straight lube.

RustyJC

Well, let's see if I can clear up a few things. I've pulled out the owner's manual (we don't need no stinkin' directions! ) and find:

The Dana 70 and 80 come from the factory with straight 90 weight dino hypoid gear lube. Therefore, my earlier post stating that they come with 75W-90 dino lube was in error.

Page 161 states, "For all trailer towing and heavy duty applications it is strongly recommended that the factory fill rear axle lubricant be replaced with an SAE 75W-140 synthetic gear lubricant. Mopar Synthetic Gear Lubricant is of this type."

Most users who switch from dino to synthetic and elect (for whatever reason) not to go with the 75W-140 recommendation above will use a 75W-90 synthetic with good results.

Does this help?

Rusty

4RGSP

I would agree with you Rusty. However, the brain surgeons that the Dodge dealership has appears to believe when I say synthetic, I really mean Dino 90.