Differential fluid?

Instrumental

Original poster
Member
Jan 29, 2012
268
I'm doing 100k maintenance soon and stocking up on supplies. I have my Auto Trak II for the transfer case, but I'm really not sure what 75w-90 to use, and searching didn't turn up much info here.

So, open question, what recommendations for the differentials?
 

hockeyman

Member
Aug 26, 2012
726
Agreed. I used Valvoline 75w90 full synthetic that I purchased at Autozone. Worked great!

Shop around too. You might find synthetic gear oil cheaper at Walmart.
 
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Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
You have a 9-7x, which means that you have the limited slip rear differential. Check the oil you buy if it has the additive for limited slip diffs (some do, most don't). If not, you must add some as per directions. Any good quality synthetic 75w90 + additive will work.
 

tblazerdude

Member
Dec 4, 2011
321
BlazingTrails said:
If it is indeed a LSD you need to use GM # 88862624 Ls fluid. Anything else will cause it to whine.
It won't "whine" if you use different fluid. There is enough old, dirty, fluid left in there to provide what you need. A factory fill would be a different question. If you do choose a lubricant without a limited slip additive it will allow for more slip. Mobil 1, valvoline, and the GM fluid as well as some others come with the additive pre-mixed in. They do sell posi-traction/limited slip additive at the dealer. This does not apply to the "locking" differential. Us regular non-saab, non-ss owners dont need any of it. :smile:
 

Instrumental

Original poster
Member
Jan 29, 2012
268
Well, probably no factory left in there. I changed it at 50,000. Used brake cleaner to through clean it out before refilling with Lucas synthetic. I don't have complaints, but I'm always looking for more information.

With the LSD, maybe I should peak in at the SS forum.
 

IllogicTC

Member
Dec 30, 2013
3,452
If one needs to confirm if they have the locker, watch for RPO code G80 in the glovebox. G86 is the LSD.

The G86 DOES take additive (I believe 4 ounces). As for the G80 locker, here's a TSB from GM on the subject:

Code:
LOCKING DIFFERENTIAL LUBRICANT (SERVICE INFORMATION) #91-4-109
SUBJECT: LOCKING DIFFERENTIAL (G80) LUBRICANT - (SERVICE INFORMATION)
VEHICLES AFFECTED: ALL LIGHT TRUCKS EQUIPPED WITH G80 REAR AXLE ALL YEARS
Some light duty trucks equipped with locking rear axles (G80) may exhibit rear axle chatter, especially when turning a corner from a stop.
This condition of alternate engagement and disengagement of clutches in differential assembly is usually caused by contaminated axle lubricant.
To correct this condition, drain and refill the rear axle with SAE 80W-90 GL5 (P/N 10950849).

The use of any additive in locking rear axles (G80) is not recommended. Rear axle additives are designed for use in limited slip differentials which are normally installed in cars. All light duty trucks equipped with RPO G80 make use of a locking differential and the use of additives will delay the engagement of the locking mechanism and may decrease axle life.

VEHICLES/COMPONENTS INVOLVED: ------------------------- ---- Some light duty trucks equipped with locking rear axles, RPO G80.
SERVICE PARTS INFORMATION:
Part Number Description ----------- ------------------ 10950849 Lubricant, Rear Axle (1 litre)
Parts are currently available through CANSPO.
WARRANTY INFORMATION:
As specified in Light Duty Truck Maintenance Schedules, locking rear axle fluid drain and refill is required owner maintenance at the first engine oil change. Failure to drain and refill the rear axle as specified may contribute to a later axle chatter condition. Refer to the appropriate Light Duty Truck Maintenance Schedule or service manual, section OB, for further details on change intervals.
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.
 
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Instrumental

Original poster
Member
Jan 29, 2012
268
I do have the LS, but reading this now I wonder if I should get regular for the front, as in no additives. Pretty sure I put the same in both last time.
 

littleblazer

Member
Jul 6, 2014
9,265
Regular in the front is fine. I have mobil 1 in both, no problems yet. As for the LS additive, I think mobil says if your manufacturer calls for the additive, you still need to add it, I believe.

BTW my rear is open, no g80 or ls.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
If you get a bunch of the oil with the additive already mixed in, you can use it in the front diff. It won't do anything. The additive, if required,is also available over the counter at parts stores.
 

BlazingTrails

Member
Apr 27, 2014
19,409
I ran mobile one for a month and I had a light whining noise coming from the rear end. According to other forums and GM the fluid I mentioned above is the only one that gets rid of it. I have the 9.5" ss 4.10 rear axle. That is my personal experience and the same info you will find on other forums. Take it or leave it. :smile:
 

Instrumental

Original poster
Member
Jan 29, 2012
268
That was my question, would the additives be bad for the front. If no, I'll keep my life simple and buy all the same.

Mobil 1 does have a LS version now. It was on my short list.
 

littleblazer

Member
Jul 6, 2014
9,265
I'm running the mobil 1 ls 75w90. The additives won't hurt, but you'll still need the LS additive in the rear diff like said. Some where it says in the product description, and I can't recall where, "for maximum limited slip performance, add manufacturer reccomended additive" or something like that. Will it work? Yea, there will be chatter though like said. Could also maybe fail (probably not though) (I spent months before deciding what to use in mine, tons of reading on these trucks, full sizes and so. I had a lot of spare time)

On a side note, I think the gm grape juice has the additive in it, but I think it's overpriced, must be the grape scent.
 
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Instrumental

Original poster
Member
Jan 29, 2012
268
Decided to go with Amsoill, local shop carries it, that was convenient. Picked up the slip lock additive, figure I'll add a squirt of that in the rear, can't hurt.

Did the front diff today, no problems there. Came out pretty black, has somewhere around 50,000 miles on it.

Also did the transfer case, and my drain plug stripped despite my best efforts. I was able to use a miti vac to get most of it out, so problem solved.

Gotta do the rear next time, had to move to the wife's MKZ. Did front pads and rotors and rotated tires.
 

Instrumental

Original poster
Member
Jan 29, 2012
268
Finished it yesterday. Did the Amsoil Severe Gear and maybe 2 ounces of their Slip Lock additive. Did the figure 8s on the test drive. Drove to church and back this morning, seems fine so far. I'll check back in on this after a few weeks.
 

triz

Member
Apr 22, 2013
746
I have the Severe Gear in there as well when I swapped to the G80. Had not thought about it till now. It's been a little over a month now.
 

awt123

Member
Jan 24, 2015
5
Ok, I am looking at changing my rear diff fluid and I looked in the glove box and I don't see either code. I have an 03 GMC Envoy XL with the 4.2. Can someone help me figure this out??

Thanks
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Welcome to the Nation!

It doesn't matter. It will use 75w90 Synthetic gear oil. Very few have the limited slip (SS, 9-7x)
 

djthumper

Administrator
Nov 20, 2011
14,950
North Las Vegas
Ok, I am looking at changing my rear diff fluid and I looked in the glove box and I don't see either code. I have an 03 GMC Envoy XL with the 4.2. Can someone help me figure this out??

Thanks
What ae you looking for?
 

BlazingTrails

Member
Apr 27, 2014
19,409
GU6 is the standard "open" (non locking) differential, it requires no special fluid. You can run any 75/90 weight you desire.

Edit: I meant to say 3.42, however as stated above whether locking G80 or open diff you can use any 75/90 weight.
 

smt 59

Member
I would not use anything but Amsoil severe gear fluid, I change all my fluids every 50k and when I drained the rear end it was like the day I put it in. I have the G80 locking diff, when you use the Amsoil you do not need to add any other additives for any reason. Get onto the Amsoil website and read up on it, all oils are NOT the same.
 
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awt123

Member
Jan 24, 2015
5
Thanks Blazing Trails! I have been looking to find the codes and haven't been able to find any. This helps a lot. Will have to start looking at which fluid to by. Kind of on a budget. Daughter is getting married next month.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
You'll be fine with regular 75w90 synth gear oil.
 

streetbober

Member
Jul 18, 2020
16
ga
I do have a question for yall. I have 80-90 weight marine-grade oil that meets GL4. can I use this in the rear differential?
 

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