GM 2500HD 75w-90 or 75w-110

[Stewart Fan]

I need to change the gear oil in my 2011 2500HD. GM recommends a synthetic 75w-90 for the 11.5" AAM. Currently about 40K miles on M1 75w-90.

Most of this trucks miles are towing a fifth wheel or boat. Both are 10,000+ lbs which is about 60% of what the truck is rated to tow.

I'm planning on another run with 75w-90,but I also see the 75w-110 is a pretty popular choice.

 

[MolaKule]

The 75W110 is a good all-around grade and that is what I would recommend.

LE, Amsoil, and Redline all have some very good 75W110's.

 

[stockrex]

My camper is around 8000 lbs, I am going to do this with mobil 75w90.

both are fine, just make sure it does not have any slip addy.

Any quality synthetic gear oil will work fine.

 

[Kawiguy454]

With that load I would do the M1 75-110 or even 140. For those heavy loads its just more safety margin.

A guesstimate of how its working now would be to haul the load a decent distance and when you stop for gas put your hand on the diff and feel how hot it is. If its really hot from friction its a bad thing.

 

[CT8]

75W-140.

 

[stockrex]

Originally Posted By: Kawiguy454
With that load I would do the M1 75-110 or even 140. For those heavy loads its just more safety margin.

A guesstimate of how its working now would be to haul the load a decent distance and when you stop for gas put your hand on the diff and feel how hot it is. If its really hot from friction its a bad thing.


Another option is to use a laser temp sensor,
just point aim and shoot and you have the temp.

 

[CarbonSteel]

Pablo has posted here more than once that 75W-110 is the viscosity that 75W-90 was before the J300 tables were updated. I would not hesitate to use 75W-110 in place of 75W-90 and Amsoil Severe Gear is arguably the best gear oil on the market. I have Amsoil in both of the axles in my F-250 (75W-110 in the front and 75W-140 in the rear).

 

[wander2039]

On the Class C was just going to replace with 75w-90 and it weighs 12k. Took it's temp once and wasn't high at all with the stock fill.. around 150 I think. The thicker lube could make it run hotter?

 

[zeng]

Originally Posted By: Eric Smith
On the Class C was just going to replace with 75w-90 and it weighs 12k. Took it's temp once and wasn't high at all with the stock fill.. around 150 I think. The thicker lube could make it run hotter?


150F would be nice and normal.
But I would personally opt for xxW110. At increased 155-160*F ish ,if any , operating viscosity and MOFT would be even higher than before offering stronger wear protection. Maybe it's just me.

 

[stockrex]

what is the temp range your operate at?
Your rear end will be fine with any of weight. If you are worried about it, just change at an extreme duty interval.

 

[mjoekingz28]

It seems all of these 'new and odd' weights are for the PCM now a days. The metals and components will likely keep chugging as long as good quality fluid of ample quantity is used.

 

[TiredTrucker]

Just for comparison purposes... semi trucks yanking around 80,000 lb of truck and load use 75w90 synthetic differential lube. The same Mobil 1 or other brand of synthetic 75w90 you get off the shelf at the parts store. Most are factory filled with the stuff. Meritor, who made mine and was factory filled with M1 75w90, will automatically extend the warranty on the diffs from the normal 500,000 to 750,000 miles if one uses synthetic 75w90, and recommends a 500,000 mile OCI on them (though my comfort zone is 300,000 miles). Hence, I use 75w90 in all my diffs from my car, my pickup, on up thru my commercial semi trucks. I haven't had a differential problem in 2 decades and 4 commercial semi trucks. My current Chevy 2500, and my previous one, do just fine on 75w90 synthetic.

 

[clinebarger]

I have always ran Mobil 1 75W-90 in my AAM 11.5" with LS additive with no issues, Over 300,000 miles, At least 100,000 of those towing a 13,000# Big Horn 5th wheel.

The AAM finned aluminum that comes on the Dodge HO diesels will fit GM 11.5" diffs, I run one on mine..... AAm Diff Cover

 

[TiredTrucker]

At least with the newer 2500HD rears, no LS additive needed. Drop a plug, drain, replace plug and fill up. Nice.

 

[messerchmidt]

amsoil severe gear 75w90 or 75w110 - your preference. in a colder climate, perhaps the 75w90 is a better choice. either would work fine.

use a LS additive if needed.

 

[BoiseRob]

In my 2007 2500HD Classic LBZ, I've run Schaeffer's #167 Full Synthetic 75w140 since new. Follow the link...

http://www.schaefferoil.com/full-synthetic-lube.html

 

[zeng]

Originally Posted By: BoiseRob
In my 2007 2500HD Classic LBZ, I've run Schaeffer's #167 Full Synthetic 75w140 since new. Follow the link...

http://www.schaefferoil.com/full-synthetic-lube.html

+1

 

[Stewart Fan]

I had forgotten to update this post.

I had some M1 75w-90 leftover from the last fluid change. I bought enough M1 to complete the front diff change.

For the rear I went with Severe Gear 75w-90.