Engine/Transmission (1998.5 - 2002) Thermally Stable 90W??

[Pull'nOld Iron]

While researching the materials for fluid change I stopped by the local dealer and got the parts. Seeing his $15/quart costs for fluid, I said I'll hold off and look around.



The counter guy, who has always been real helpful, indicated to be sure to get straight 90w fluid.



I looked in the service manual and it does state in the lubricant specification, SEC. 3-92, "Lubricant is a thermally stable SAE 90W gear lubricant. "



Does this precluse using a 70w - 90w lubricant even if it meets the GL-5 quality spec?



This is my daily driver but I do tow heavy loads periodically in the area of 13K - 16K.



I've been hearing a whine out of the rear end and suspect an axle or diff bearing is going out. I believe once I tear into this it will be a more involved project. Any advise on this subject will be appreciated.



Thank you, take care

 

[RustyJC]

90W might be the factory fill, but my owner's manual recommends a 75W-140 synthetic for heavy towing applications. Since we pull a 13,500 lb 5th wheel regularly, I went with Royal Purple 85W-140 synthetic (I'm not worried about cold performance here on the Texas Gulf Coast), and it works great. I didn't even have to add any friction modifier for the limited slip since the Royal Purple has it built into the formulation.



75W-90 synthetic is commonly used by a lot of members here on the board, including many who tow some pretty good loads. The Royal Purple (and a number of other synthetics) is available as a 75W-90 as well.



Rusty

 

[Pull'nOld Iron]

Rusty

Thanks,



I see you have an 02.



Not having the benefit of looking at your Manual, I didn't see towing recommendation in my manual. Is there a specific section you were looking at. Maybe I need to look a little harder at the fine print somewhere.



I'm still thinking the counter guy was doing what he's suppose to in selling his stuff. With all these new fangle specs... ..... I'm wanting to be sure on my 99.



Thanks for your help, I think I need to stop by the old Wally Mart and see what specs I can see and if they carry any synthetic.



Thanks again, rattle on.

 

[RustyJC]

I don't have the truck with me at work today, but if you look at the index under "Towing" or "Trailer Towing", there's a section that deals with trailer tongue weight distribution, etc. In this section, it makes a recommendation for synthetic axle lubricant for heavy towing applications. This was in the owner's manual for my 1996 3500 V-10 as well. Maybe someone with his owner's manual handy can point us to the specific section and page number.



Rusty

 

[Pull'nOld Iron]

Thanks

Thanks for the heads up.



I'll check when I get to my truck also.