Mobil synthetic 75W-90 in a G80 Locking diff

[zeng]

Originally Posted By: wtd
Years ago I used Mobil 1 diff fluid in the rear diff of my 98 chevy K1500. At about 55,000 miles I started to get some rear end whine. At about 75,000 miles it got bad enough that I had it checked out and it was discovered that my pinion and carrier bearings were shot. This was on a truck that hardly ever hauled anything or pulled a trailer. Never anything heavy.

After the repair I went back to a conventional diff oil and have not had any problems since. I'm not saying that Mobil 1 was to blame but it didn't make me want to use it again.

Wayne

I wouldn't blame M1 either, or its add pack/synthetic base oils.
It's the low operating viscosity (by extension MOFT) typical of 75W90 in relation to conventional 80W90/SAE 90 that kills ..... a gear train........ but most Americans manage to get away with it.

 

[KenO]

Originally Posted By: wtd
Years ago I used Mobil 1 diff fluid in the rear diff of my 98 chevy K1500. At about 55,000 miles I started to get some rear end whine. At about 75,000 miles it got bad enough that I had it checked out and it was discovered that my pinion and carrier bearings were shot. This was on a truck that hardly ever hauled anything or pulled a trailer. Never anything heavy.

After the repair I went back to a conventional diff oil and have not had any problems since. I'm not saying that Mobil 1 was to blame but it didn't make me want to use it again.

Wayne



You want to blame Mobil or Synthetics because you went too long on your diff fluid change, and had diff issues? Got it.

 

[4WD]

Used M1 gear oil for 20 years and owned 6 GM 4WD's in that time period ...

 

[BrianF]

I am currently using Amsoil 75w90 longlife in my G80 equipped Tb. I bought it because the other name brand synthetic gear oils were going for 24-30$ a liter at most stores. The Amsoil was 15$ a quart so it was much cheaper. I have about 70,000km on it now and it has worked just fine. The locker engages and disengages as smooth as it ever did.

 

[wtd]

Originally Posted By: KenO
Originally Posted By: wtd
Years ago I used Mobil 1 diff fluid in the rear diff of my 98 chevy K1500. At about 55,000 miles I started to get some rear end whine. At about 75,000 miles it got bad enough that I had it checked out and it was discovered that my pinion and carrier bearings were shot. This was on a truck that hardly ever hauled anything or pulled a trailer. Never anything heavy.

After the repair I went back to a conventional diff oil and have not had any problems since. I'm not saying that Mobil 1 was to blame but it didn't make me want to use it again.

Wayne



You want to blame Mobil or Synthetics because you went too long on your diff fluid change, and had diff issues? Got it.

I don't know how you came to that conclusion because that is not the case. I actually used to change my diff fluid every 15,000-20,000 miles which is way more often than it calls for. I also had the diff fluid changed at my first oil change per the owner's manual. Next time you might try getting more info before becoming an [censored].

Wayne