2003 GMC Sierra rear differential oil

[carbon12]

Doing brakes on my truck and found axle seal seeping on right side. Parking brake was oily. YouTube video of axle removal didn't look toooo bad. Would have to drain and fill rear diff.

I'm thoroughly confused as to what gear lube should be used for rear differential of a 2003 GMC Sierra 1500 4 WD with Z71. It's got a locking rear differential, not limited slip. Pretty sure it's the G80. Some things I read say use no LS additives. What if the oil already has some additive in it? Is Mobil 1 or Valvoline Synpower 75w90 OK or do I have to go to dealer for the GM product? What oil have you had success with?

 

[dogememe]

in the trucks you don't need any additive, any quality 80w-90 or 75w-90 gear oil will be fine. i've used royal purple and valvoline gear oils in various gm applications in the past with no trouble.

 

[Gasbuggy]

You don't need any additive but the locking diff doesn't care if there is additive in there. Run anything you want. If it were me, I'd spend a little extra for a synthetic to see if my MPG goes up a little bit AND I would change the front diff fluid at the same time.

I bought the Mobil LS fluid for my CTS-V, which is known to tear up diff fluid. If you run it hard, Redline Shockproof is well respected too.

 

[Alex_V]

Amsoil Severe Gear 75w90.

 

[dlundblad]

Supertech 75w-90. $5.50 a quart. Full synthetic.

 

[Rat407]

 

[JHZR2]

Originally Posted By: Alex_V
Amsoil Severe Gear 75w90.


+1.

Or else delvac 1 75w-90.

 

[14Accent]

According to my Amsoil rep, the severe gear 75w140 is better than the 75w90, and can be used interchangeably. I have no idea if that's accurate or not, I still use the XXw90 where called for.

 

[4wd]

Originally Posted By: JHZR2
Originally Posted By: Alex_V
Amsoil Severe Gear 75w90.


+1.

Or else delvac 1 75w-90.


In my 2010 GMC now for 2-1/2 years … and just bought to replace FF in 2017 Tahoe … got it for $33/gallon …

 

[UNC151]

Originally Posted By: 14Accent
According to my Amsoil rep, the severe gear 75w140 is better than the 75w90, and can be used interchangeably. I have no idea if that's accurate or not, I still use the XXw90 where called for.
75W-110 would be "interchangeable" with 75W-90 because 75W-110 is at the upper end of the viscosity range of 75W-90 before the J306 tables were updated some years ago. While 75W-140 would likely not hurt your axle, it is considerably thicker than 75W-90. If it were mine, I would use Amsoil 75W-110 and not look back.

 

[4wd]

I used Mobil 1 90’s in GM G80’s for many years … always noticing the 140 was much more expensive … figured all along this might be the reason

 

[benjy]

Exxon Mobil refines as well as makes a LOT of different lubes + supplies them to whoever whoever!! those specs look good but what product are those specs for + what date are they??? after the "fake synthetic" BS with castrol most "synthetics are the cheaper group variety highly refined + processed CRUDES good but not as good as the real deal!!

 

[4wd]

Originally Posted By: benjy
Exxon Mobil refines as well as makes a LOT of different lubes + supplies them to whoever whoever!! those specs look good but what product are those specs for + what date are they??? after the "fake synthetic" BS with castrol most "synthetics are the cheaper group variety highly refined + processed CRUDES good but not as good as the real deal!!


Look at the 90 and 140 side by side … 140 looks pretty close to the PAO blend …

 

[DONWATERS]

I always use the 75w140 or 80w140 conventional lube in rear axles. I have several jeeps, its what the shop that does gear swaps recommends. They say do not use synthetics. I have had leaks using synthetics in the past with brand new seals. If you have a gov lock or detroit style locker, no additive, only need an additive if it has clutch packs.

I just re read, you have the 1500, thats a light duty rear axle, those gov locks explode if you have one wheel on loose ground. The loose wheel spins, centrifical force locks the diff and it explodes. Use thick lube. I have the 1 ton full floater 14 bolt in mine. Its a huge upgrade.

 

[4wd]

Originally Posted By: DONWATERS
I always use the 75w140 or 80w140 conventional lube in rear axles. I have several jeeps, its what the shop that does gear swaps recommends. They say do not use synthetics. I have had leaks using synthetics in the past with brand new seals. If you have a gov lock or detroit style locker, no additive, only need an additive if it has clutch packs.

I just re read, you have the 1500, thats a light duty rear axle, those gov locks explode if you have one wheel on loose ground. The loose wheel spins, centrifical force locks the diff and it explodes. Use thick lube. I have the 1 ton full floater 14 bolt in mine. Its a huge upgrade.


Some say this and for many it works … but a few points
1) The big 3 recommended synthetic gear lube for many years now, some before motor oil … rear ends get neglected
2) In the industrial lubricant world … synthetic is king … it is certainly not weak sauce like they think
3) My only complete lubricant failure (lost entire differential in just over 30k on lube) was Pennzoil Conventional and the oil looked like 0w5 (That’s in decades of driving pickup trucks)
4) On a GM, Eaton might be OK with dino … but the “system” OEM like AAM will not be

 

[dlundblad]

Originally Posted By: Rat407

Interesting. Are these easier to use?