Can I user 75W140?

[Casey Balvert]

I know that both the owner's manual and service manual specify 75W90 synthetic for the 11. 5 rear axle in the new trucks. However I would feel better towing with 75W140 in it. Interestingly, DC recommended the heavier stuff for my old truck while towing. What detrimental effects would there be if I switched over to the heavier lube? Or would the recommended oil provide all the protection that I need?



Happy New Year all.



Casey

 

[nickleinonen]

fuel economy may go down with the heavier. being that this rear axle is pretty much identical, what GM recomends for their 3500's is their "grape" juice. [purple in color and smells like grape according to the dieselpage guys] but i'd be some mobil1 or amsoil or redline in full syn. rear gear oil in the weight you want will work good. .

 

[Badunit]

I have always thought that as long as the lower number was the same as that recommended (or close) and the upper number was the same or higher, you won't do any damage. I've also thought that having a higher second number (i. e. , 140 vs 90) would be beneficial from a wear standpoint and for higher loads but maybe not from a fuel-efficiency standpoint. Anyone have anything that either backs this up or refutes it?

 

[amsoilman]

I have customers with 18 wheelers using the 75W-90 gear lube, so I'm sure our smaller trucks are just fine using it as well. I just installed the synthetic fluids throughout my own 03' truck. Not worried in the least.



Wayne

amsoilman

 

[Fireman]

It stands to reason that the heavier lube would be beneficial when towing heavy. You might consider changing to a heavier lube just before departing for the Gulf, and if you don't have any other long trips planned, change back when you return home.



Just a thought,



Fireman