M1 75w90 2000 Rear Diff 100k

[Doug Hillary]

Jim,
condemnation limits will vary somewhat from Manufacturer to Manufacturer. It would be fair to say though that the "limits" are quite universal in that the concentration is the deciding factor

These are limits from Eaton concerning truck diffs:

Viscosity at 100C - 20% +/- from new
TAN - increase of 2 over new lube
Phosphorus - 30% decrease from new
Iron - 1500ppm
Copper - 250ppm
Chromium - 10ppm
Silicon - 130ppm and other WMs are high
Sodium - 50ppm
Aluminium - 150ppm
Water 1% by volume

I used this lubricant (Mobil 75W-90) and Castrol's equivalent for many years in my Class 8 trucks. I did not carry out OCs at all before 1m kms (620k miles). Both the castrol and Mobil lubricants performed the same - both are great products!

This UOA was from one diff (front of tandem) and taken at 1.04m kms (646k miles) over four (4) years:

Iron - 569ppm
Aluminium - 8ppm
Chromium - 2ppm
Copper - 40ppm
Lead - 5ppm
Silicon - 138ppm
Sodium - 10ppm
Tin - 2ppm

TAN - 2.4
Water - 0.15%v
Viscosity - normal

Most diff lubricants are changed out far too soon - water may be an issue with some vehicles however if breathers are submerged from time to time! "Unpracticed" lubricant contamination can occer too for the unwary!!!

The 1m (620k miles) OCIs worked very well for me over many years and many millions of kms/miles. My trucks were always loaded to 42000kgs and I never had a differential or wheel bearing failure when using synthetic lubricants. Operating temperatures were usually less than 80C

 

[Jim Allen]

Thanks Doug! Useful info. I might query some other axle manufacturers for some more specific limits, assuming my old connections still have jobs ( : < (

 

[Jasper8146]

I agree with the later (than 3K) first change interval on the diff. For 2003 Acura MDX rear diffs, the initial change interval is 7500 plus another one at 15,000 and thereafter at 30,000 intervals. I saw a thing on Amsoil's site to the effect most differential wear occurs in the first 7500 miles although I could see that number might vary from manufacturer to manufacturer. I recently did a change myself after 40,000 miles on the VTM4 gear fluid with 112k on the vehicle and the fluid was absolutely pristine, no wear debris at all on the magnet. Next time, before I change I will probably do a UOA at around 30k miles more and see what it shows.

 

[Loobed]

Originally Posted By: REDDOG
I agree with LargeCarManX2. I did the same 100k interval with Mobil 1 75W-90 in my K1500 and it's still kicking with 180k on the odo.

The iron may look a little "shocking" but consider the work this diff has done for 100k. All things considered I think it served you well.



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