75w90 vs 75w140

[SnowDrifter]

Without regard to power or drag, which would give the greatest service life of a differential?

I've been running through it in my head and can think of a bunch of pros and cons. But I figured I'd ask the oil nerds

2005 Chevy Tahoe, G80 rear diff. Factory suggests an 75w90. But these things also have a habit of breaking. And I plan to keep the vehicle for a long, long time.

Other thoughts: If a thicker fluid is appropriate, would it make sense to fill slightly higher than the factory level to account for the thicker film on the non-moving parts to keep the working level the same? This vehicle specs an amount below the fill hole, not dribbling out as most do, so it's easy to tweak how much fluid is is there.

 

[oldhp]

Towing??? 75W140. Not towing??? 75W110. I would use Red Line gear oil. Done.

 

[zeng]

75W140 for increased service life , whilst avoiding gear whines.

 

[IndyFan]

I would not fill it above the factory level. If not towing or hauling heavy loads frequently, 75w90 will be fine, if that's what's specified by GM. If not comfortable with that, then go with the 140 and don't worry about it.

 

[zeng]

On fill level ,yes it's 'better' for the differential components in particular all the bearings within, to make it slightly higher as suggested.

 

[Taildragger]

Gale Banks has some great info on diff covers and fill levels; HERE

 

[Snagglefoot]

Did someone say 75w140?

 

[dave1251]

Unless it's severe duty I just use 75W110 for occasional towing hauling. But that is just me.

 

[BrianF]

The diff capacity is finite so regardless of oil weight used, it can only hold so much debris before the oil needs to be serviced. I suppose the heavier weight would add some life expectancy to a heavily used diff.

I used 80w140 (9$ a liter in a 20L pail) for my ram 1500. I towed very, very heavy and the diff was doing great when we sold it. I had plenty of it left over so that is what my 3500 gets in the rear diff. I like it but will eventually switch to 90 weight so I do not need different weights floating around.

 

[64bawagon]

+1 on the Banks video's, some great info there backed up by testing rather than rhetoric.
I dont think I know as much about gear oil requirements than the people that designed, tested, built and warrantied the differential, if they say 75W90 thats what I use.

 

[MetalSlug]

Originally Posted by Taildragger
Gale Banks has some great info on diff covers and fill levels; HERE


I just start watching it just now, very interesting, cant wait for part 3 when he come up with the final thought , but the way he say, I think he like what ever come stock from the factory and factory recommend gear oil weight..no need fancy aftermarket stock diff.

 

[Y_K]

Sure.. Especially with the deficiencies of the Ford 8.8 design that this animated documentary cartoon doesn't even mention. This Banks dude, he still needs a good click rate, doesn't he?

 

[64bawagon]

I would be willing to bet that Banks will announce his new line of diff covers after video #3. I cant imagine he has spent all that time and money just for giggles.