I thought this was interesting reguarding M1 75w90!

[Chris B.]

I work at a Wal Mart Distribution center and it has it's own shop to work on the 300 + semi's there. I asked the shop formen what they use in the diffs and he said Mobil 1 75w90. That is what I use in my 2003 Silverado. I was told and have read on here that 75w90 was not heavy duty enough if you pull alot. Well why would Wal Mart use it in a tractor that pulls 40,000 pound trailers every day if it was not heavy enough? He said they analyse it every time they change it out and the M1 shows the best wear of anything they use.
So it looks like M1 75w90 is fine to use in heavy aplications after all.

 

[Doug Hillary]

Hi,
there is another thread on here on this subject please refer to that

I use this grade synthetic gear oil in my OTR trucks at 500hp & 42500kg and up to 40C+

Have done for years

Regards

 

[Ken2]

Chris,

75W-90 gear oil works in heavy truck differentials because the gears and bearings were made for that viscosity oil. If a differential is made for 75W-140, even a light duty Ford, then that's what it needs. I've run 32,000 hp gears with ISO 100 turbine oil (about 30 wt), because that's what they were made for.


Ken

 

[Chris B.]

I read on here and I don't remember who said it but they told me to change out my diff gear oil to something heavyer because the 75w90 was not up to heavy towing. My truck calls for 75w90. I didn't and still don't really know much about gear lube and when I found this out it made me a little mad that I got bad advice. My truck can pull 9,000 lbs and 75w90 will handle that fine. I guess life is full of bad advice, I even have given some.

 

[Bio-T]

Chris,
Not sure what vehicle you have or what advice you recieved.
But on all 1995 and above Ford F-250/350 has a TSB on using the 74W-140 synthetic oil. The manual states the 90w, but the TSB supercedes it. My 01 states the 140w Synthetic,on a metal tag on the pumpkin. I just use the Amsoil Synthetic 140W and don't worry about it.
So if yours is a GM/Dodge product, this is not applicable.

 

[pacem]

I will use that in my F250 differential.

 

[S2000driver]

I use it in my S2000's Torsen-2 LSD.

 

[Chris B.]

My truck is a 2003 Silverado. What I'm wondering is why would someone say 75w90 is not up to heavy towing when it is used in big rigs, it dosen't get any more heavy duty then that?

 

[Doug Hillary]

Hi,
Chris.B - as mentioned earlier ( and in the 75w-90 V 140 thread ) I use 75w-90 synthetic oils in the diffs of my heavy trucks. This is not a foolhardy move - it is a good sound economic one!

The manufacturer's recommended range for diff oils ( all MIL-L-2105D> )is as follows;

75w-90 Synthetic @ All Temperature ranges

75w @ -40F to -15F
75w-80 @ -40F to 80F
75w-90 @ -40F to 100F
75w-140 @ -40 and above
80w-90 @ -15F to 100F
80w-140 @ -15F and above
85w-140 @ -10F and above

It can be seen that the synthetic 75w-90 lubricant is very robust and has a very wide application

The "replace and monitor" UOA limits ( for mineral/synthetic ) are;

Viscosity @ 100C @ 20%+/20%- from new oil
Phosphorus @ 30% decrease from new oil
TAN @ +2 over new oil
Iron @ 1500ppm
Copper @ 250ppm*
Chromium @ 10ppm
Silicon @ 130ppm + high wear metals
Sodium @ 50ppm
Aluminum @ 150ppm*
Water - 1% by volumn
* Single speed axles in OTR use

The synthetic 75w-90 is a very robust lubricant as mentioned earlier and it should be remembered that MOST diffs run very cool for most of their life. And the modern diff is a very durable component

Grey haired fellows on here may remember that many cars in the 50s, 60s, 70s required bearings or a C/W & pinion at under 40k miles! Especially those labeled "Made in Britain"

Regards

 

[Chris B.]

Thanks Doug some good stuff! I'll stick with the Mobil 1 75w90.