Front and Rear Differential Fluid Change

autumn walker · Aug 8, 2012

I'm replacing the driver's side inner axle seal tomorrow night and will be changing the front / rear differential fluid while I'm at it (front has been leaking and I might as well keep the fluid changes in sync).

The owners manual states 75W-90 and meeting GM Speciﬁcation 9986115; however, nothing but the expensive "grape juice" meets that spec. What are you guys running in your differentials? Would a Mobil 1 or Amsoil 75W-90 work the same?

Approximately how much fluid will I need in the front and in the rear differentials? I want to make sure I have enough before I go pulling the truck apart.

Zach · Aug 8, 2012

Mobil 1 75w90 synthetic is the same as the factory gear oil and a lot cheaper than buying from the dealer. Front will take two bottles and the rear three bottles

alrock · Aug 8, 2012

For my H3 I used this: http://www.amazon.com/Red-Line-5790...734&sr=8-1&keywords=75w-90+synthetic+gear+oil and cheaper than the GM stuff. It meets the GL-5 spec required of your diffs and it has the friction

http://www.redlineoil.com/product.aspx?pid=133&pcid=4

Red Line Gear Oils, with the exception of the75W90NS, and 75W140NS, already contain friction
modifier required for operation in limited-slip differentials. Additional additive is not usually required, but
newer units or those with more lockup capability may
require 1-4% additional Red Line Limited-Slip Friction
Modifier. If Red Line is not available, the manufacturers
recommended friciton modifier is compatible. Do not
add addtional modifier unless necessary, as too much
will result in excessive wheel spin.

75W90 Gear Oil - the preferred product in nearly all carand light truck differentials, both conventional and limited-slip. 75W90 is preferred for most racing applications.
It contains friction modifier which is recommended for
limited-slip units. 75W90 Gear Oil can be used in many
transmissions and transaxles; however, other Red Line
lubricants have better frictional properties for rapid synchronization. Exceeds API GL-5

All that said, I'm certainly not an expert on the H2 diff requirements.

autumn walker · Aug 9, 2012

Turns out I can't find Mobil1 anywhere here.

So far I have the GM stuff at $16.65 per 946mL bottle and Castrol SYNTEC at $6.79/bottle.

Should I just suck it up and buy the GM stuff?

alrock · Aug 9, 2012

Doesn't sound like a bad price at all for the GM product.

[__--MUD--__] · Aug 9, 2012

thats not a bad price on the GM. the grape juice shouldn't be much more than that either.

autumn walker · Aug 9, 2012

[__--MUD--__];60805 said:
thats not a bad price on the GM. the grape juice shouldn't be much more than that either.

AFAIK this is the "grape juice". That's how the guy on the phone referred to it when I asked.

Scarsman · Aug 9, 2012

When I had the rear axle replaced at the dealer the mechanic told me they put in a B&M synthetic oil in mine. That was done by GM under warranty.

twinmill28 · Aug 9, 2012

I Googled Mobil 1 75w90 synthetic and found they also have an LS version--is that the synthetic vs. regular?

Also, what's "grape juice"? Is that Royal Purple, or just a nick name for the factory stuff, which I guarantee either way WILL NOT smell anything like grape juice.

autumn walker · Aug 9, 2012

twinmill28 said:
Also, what's "grape juice"? Is that Royal Purple, or just a nick name for the factory stuff, which I guarantee either way WILL NOT smell anything like grape juice.

Nickname for the factory stuff. I don't recall it smelling like grape juice either, but that's what people are now saying.

auggie mathis · Aug 9, 2012

We use mobil 1 75w 90

Zach · Aug 9, 2012

Originally when they came out with the synthetic diff fluid customers were complaining about a propane smell coming from the vehicle. That is why they added the grape scent.

autumn walker · Aug 9, 2012

dealership gave me a great deal on the fluid (cheaper than the amsoil through a friend).

2 bottles in the front and 3 in the rear, just like Zach said!

Renagade132 · Jan 24, 2014

Great information to have for future reference, thanks!

Diluck · Oct 5, 2016

Total cost to do the front and rear hummer h2 diff axle with 75w90 synthetic 5 bottle cost $97.00 CAD to put in labor the max $54.00 CAD total cost $150 CA

4speedfunk · Oct 12, 2016

Don't be tempted to run natural oil, especially if you live in a colder climate. Diffs (especially fronts) will sometimes dart left & right in cold weather....usually first thing in the morning. Once the oil gets warmed up, the spider gears spin freely but, they can stick if you run natural 85w-90 below 30F degrees. My Burb has a 14-bolt rear, and my H3 has a Dana 44 front...and both of them do this in cold weather. After reading a zillion Google hits on this topic...the consensus is to run full-synth 75w-90. I will be trying this out over the winter to see if the problem goes away.

06 H3 · Oct 12, 2016

I run 85w140 in both diffs. I've had a good chat with a long time diff builder. He's been doing diffs for 30+ years and his family has been doing it longer. He said 85w140 will ALWAYS leave a film layer on the gears. They would leave 2 3rd members in a shop for months at a time. 75w90 gearset will have dry gears after a week. Months could go by and the 85w140 still had the film of fluid on the gearset. Im sure in the cold this fluid would suck! Out west I can drive 300 miles straight with it being 105 degrees out. I want the thickest nastiest fluid so when it heats up it's still giving maximum lubrication.

06BlueH3 · Sep 1, 2017

So this would be okay for front and rear differentials on an H3 no lockers?

Mobil 1 104361 75W-90 Synthetic Gear Lube LS - 1 Quart https://www.amazon.com/dp/B000ONZXPK/ref=cm_sw_r_cp_api_9tHQzb6Q3HAC7

What is best for Transfer case?

Sent from my iPhone using Tapatalk

alrock · Sep 3, 2017

That will be fine even with the limited slip additive (LS). Dexron VI for the transfer case

Sent from my SM-G935V using Tapatalk

f5moab · Sep 3, 2017

When I was at GM, the fluids they used were Mobil! When Saturn started up and they went with Havoline (Chevron) there was a big stink (no pun intended). Since 2008, I have no idea what they use in the factory. That was for fluids. For cleaning agents they used whatever tested the best for the purpose. Example, GM injector and top engine cleaner came from Chevron (Techron). Just saying....

Hunner · Sep 3, 2017

F5 has spoken.

Hi there, glad to see you are still kickin, lol

06BlueH3 · Sep 3, 2017

alrock said:
That will be fine even with the limited slip additive (LS). Dexron VI for the transfer case

Sent from my SM-G935V using Tapatalk

Thank you Alrock!!

Sent from my iPhone using Tapatalk

06BlueH3 · Sep 3, 2017

Okay. The guy at GM told me to use this for my transfer case.
https://www.amazon.com/gp/aw/d/B00BK7LZYW/ref=ox_sc_act_image_1?smid=ATVPDKIKX0DER&psc=1
What are your guys experience. Should I use this or a dexron VI? My manual says Dexron III. I have an H3 2006 I5. Alrock mentioned using Dexron VI. Just confused with the GM guy mentioning a different product. I just don't want to damage my TC. I have 104,000 miles on my H3.

Sent from my iPhone using Tapatalk

Front and Rear Differential Fluid Change

Well-Known Member

Mall Crawler

El Diablo

Well-Known Member

El Diablo

Well-Known Member

Well-Known Member

Sponsor

Spilled Milk

Well-Known Member

Well-Known Member

Mall Crawler

Well-Known Member

ZAMU

Probationary Member

Well-Known Member

a.k.a. "The Jackal"

Active Member

El Diablo

Mr. Beretta

Well-Known Member

Active Member

Active Member