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Discussion Starter · #1 ·
Ok, I've searched all over the place and can't get much of a straight answer. I have an 08 Silverado 1500 with the G80 locking differential. I removed the fill plug today (5,700 miles) and saw plenty of fine metal stuck to the magnet built into the plug, and the fluid is black. I decided to go pick up some of the "grape kool-aide", was $35 per quart, so I thought I'd see what another dealership could do for me, $20 per quart. I said bring out 3. The guy brought out 3 quarts of Mobil 1 75w-90, I said that that is not what the manual calls for and he said it's the same stuff.

Well, Mobil 1 doesn't smell like the grape kool-aide, so right there it isn't the same stuff. So what should I do? I would like to put the right stuff in, the Mobil 1 doesn't meet the GM specification (don't recall which one). Any information would be appreciated.
 

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IMO, you can use 75W90 synthetic...GM or not...

I have Mobil1 for customer pay...GM grape juice for warranty repairs...



Adhesives, Fluids, Lubricants, and Sealers
Application
Type of Material
GM Part Number
Rear Drive Axle
Lubricant
SAE 75W-90 Synthetic Axle Lubricant 89021677 (Canadian P/N 89021678) or equivalent meeting GM Specification 9986115
Ring Gear
Marking Compound
1052351 (Canadian P/N 10953497) or equivalent
Pinion Gear Bearing Retainer
Sealant
1052942 (Canadian P/N 10953466) or equivalent
Pinion Yoke Splines
Sealant
12346004 (Canadian P/N 10953480) or equivalent
 

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Discussion Starter · #3 · (Edited)
Sounds like you're a mechanic, so if GM allows it, I don't see a problem with doing it myself. Thank you for the quick response. Tomorrow I'll be draining the dirty stuff and putting in some fresh Mobil 1.

EDIT: Wording
 

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Just curious, but shouldn't you have the rear-end looked at? And what made you check it in the first place? For such low mileage on the truck something doesn't seem right... something that simply changing the fluids wouldn't fix.
 

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Discussion Starter · #5 ·
Just curious, but shouldn't you have the rear-end looked at? And what made you check it in the first place? For such low mileage on the truck something doesn't seem right... something that simply changing the fluids wouldn't fix.

I checked it because I like to make sure things are running correctly. What is it you are refering to that a fluid change won't solve? When you first break in your engine you drain the oil and it's black and full of stuff, well the filter is, and you put fresh oil and filter on, fluid stays a lot cleaner during the timeframe you use that oil.

As far as having it checked out, I can look and everything and see if anything looks abnormal or not. Granted I'm not a mechanic, but if I see a tooth on the ring gear that doesn't look like the others or something like that, I will know that I need to pay attention to the rear end.

I hear stories of people grenading these G80 rear ends, I've heard mechanics say "brand new Tahoes with soccer moms driving them" and stuff like that, well, if that's even true, I suspect it was because the same fluid that was in there from the factory was still in there. I've also heard a lot of people talk about how they got a lot less than 2 quarts out of their diff, not enough fluid, heat builds up faster. So I just want to check things to make certain. It's like pulling the dipstick out of the engine or trans to see how much fluid is there, see what it looks like and smell it. That's all I am basically doing.
 

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Most G80 failures happen when there is too much right foot when one tire is in mud, on ice or in snow.

Changing the gear oil, while spendy, will help keep the gears and diff properly lubricated, but it won't stop the G80 from grenading. The life depends on use, terrain, and how heavy your foot is.
 

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I checked it because I like to make sure things are running correctly. What is it you are refering to that a fluid change won't solve? When you first break in your engine you drain the oil and it's black and full of stuff, well the filter is, and you put fresh oil and filter on, fluid stays a lot cleaner during the timeframe you use that oil.

As far as having it checked out, I can look and everything and see if anything looks abnormal or not. Granted I'm not a mechanic, but if I see a tooth on the ring gear that doesn't look like the others or something like that, I will know that I need to pay attention to the rear end.

I hear stories of people grenading these G80 rear ends, I've heard mechanics say "brand new Tahoes with soccer moms driving them" and stuff like that, well, if that's even true, I suspect it was because the same fluid that was in there from the factory was still in there. I've also heard a lot of people talk about how they got a lot less than 2 quarts out of their diff, not enough fluid, heat builds up faster. So I just want to check things to make certain. It's like pulling the dipstick out of the engine or trans to see how much fluid is there, see what it looks like and smell it. That's all I am basically doing.
Ahh, gotcha.

I asked why you were checking because I don't know of anyone that checks it with such low mileage that you have on your truck. So I wondered if maybe you had experienced an issue that would make you think to check it. Makes me think I should go check mine now. :D
 

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you need 75 90 made for locking diffs, its a synthetic gear lube, it must be used, or else it will cause damage to it.
 

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we use the mobil 1 all the time, thats all we sell, the GM stuff is way overpriced and never gets sold
 
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