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#3142874 - 10/02/13 06:40 PM Gear Oil- GM Limited Slip what to do???
Nick1994 Online   content


Registered: 02/19/13
Posts: 1587
Loc: Phoenix, AZ
I have a 1996 Chevy C1500 with 157k miles and the 5.7L Automatic with the limited slip rear end and 3.73 gears.

I doubt the differential fluid has ever been changed and I called the dealer to ask what gear oil to use, they said 75w90 with a limited slip additive, but when I called another dealer this guy, who seemed like he knew what he was talking about said not to use a limited slip additive on it since it is not a true posi (or something like that) that the dealers got in trouble for using that additive, that it caused premature wear. So I called another dealer and they said to use 75w90 with the additive.

What do I do? Do I use the additive or not?

Which brand of gear oil should I buy?
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2004 VW Beetle TDI 164k

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#3142887 - 10/02/13 06:48 PM Re: Gear Oil- GM Limited Slip what to do??? [Re: Nick1994]
HardbodyLoyalist Offline


Registered: 08/06/04
Posts: 702
Loc: Lower Alabama
Have you tried contacting GM directly? I'm interesting in seeing their response.

And if you're not supposed to use the LS additive, does that also mean you shouldn't use a gear oil that already contains the additive, like Mobil 1 Synthetic Gear Lube LS?
_________________________
1994 Nissan Hardbody -- Mobil 1 HM 5W30
1998 Ford F150 4WD -- Mobil 1 HM 5W30
2009 VW Jetta TDI -- Pentosin SuperPerformance III 5W30

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#3142890 - 10/02/13 06:49 PM Re: Gear Oil- GM Limited Slip what to do??? [Re: Nick1994]
EricF Offline


Registered: 07/14/09
Posts: 1611
Loc: SF Bay Area
Here's a question to ponder.. if they don't want you to put a limited slip additive, should you be using gear oils that already have the LSD additive in it?

I've always been told, it doesn't hurt to add it, but don't add more than the 4oz. If you don't need it, you're throwing your money away but it wouldn't cause any issues.
_________________________
1993 Ford Ranger XLT 4.0L 4x4 (240k) 5W-30 Synpower
2006 Saturn Relay-3 3.5L (85k) 5W-30 Synpower
2012 Ford Fusion SE 2.5L (39k) 5W20 M/C Semi Syn

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#3142892 - 10/02/13 06:51 PM Re: Gear Oil- GM Limited Slip what to do??? [Re: Nick1994]
skyactiv Offline


Registered: 03/02/13
Posts: 737
Loc: The Midwest
Go to Autozone and get some Castrol/Syntrax Limited slip gear oil 75W90 which is $9.99 a quart.

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#3142895 - 10/02/13 06:51 PM Re: Gear Oil- GM Limited Slip what to do??? [Re: Nick1994]
Nick1994 Online   content


Registered: 02/19/13
Posts: 1587
Loc: Phoenix, AZ
Exactly, most of the gear oils at O'Reilly's say for use in a limited slip, so confused, feel stupid.
_________________________
2004 VW Beetle TDI 164k

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#3142899 - 10/02/13 06:52 PM Re: Gear Oil- GM Limited Slip what to do??? [Re: Nick1994]
Gabe Offline


Registered: 02/22/11
Posts: 1425
Loc: Indiana
I didn't know the C1500 had the LSD option.

As for the premature wear, I wouldn't worry about it. With 220k miles on my '98, the rear differential still had the QC guy's initials wrote on it. Besides, most gear oils already have the additive in them.

Mobil 1 has worked the best for me.

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#3142915 - 10/02/13 07:00 PM Re: Gear Oil- GM Limited Slip what to do??? [Re: Nick1994]
stchman Offline


Registered: 09/25/13
Posts: 517
Loc: St. Louis, MO
Originally Posted By: Nick1994
I have a 1996 Chevy C1500 with 157k miles and the 5.7L Automatic with the limited slip rear end and 3.73 gears.

I doubt the differential fluid has ever been changed and I called the dealer to ask what gear oil to use, they said 75w90 with a limited slip additive, but when I called another dealer this guy, who seemed like he knew what he was talking about said not to use a limited slip additive on it since it is not a true posi (or something like that) that the dealers got in trouble for using that additive, that it caused premature wear. So I called another dealer and they said to use 75w90 with the additive.

What do I do? Do I use the additive or not?

Which brand of gear oil should I buy?


GM does not use limited slip differentials in the trucks.

Look in the glovebox for the RPO sticker and see if you have the code G80.

A G80 differential is a locking differential and does not require any type of additive. The fluid is the same regardless. Simply use a 75W90 and I recommend Mobil 1. The use of limited slip additive will interfere with the G80 locking mechanism and cause it to chatter badly.


Are you going to remove the differential cover or use a pump to suck out the fluid?


Edited by stchman (10/02/13 07:01 PM)
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2013 Chevrolet Silverado LTZ 2WD 5.3L
Mobil 1 5W-30
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#3142954 - 10/02/13 07:22 PM Re: Gear Oil- GM Limited Slip what to do??? [Re: Nick1994]
Nick1994 Online   content


Registered: 02/19/13
Posts: 1587
Loc: Phoenix, AZ
Definitely remove the cover
_________________________
2004 VW Beetle TDI 164k

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#3142958 - 10/02/13 07:24 PM Re: Gear Oil- GM Limited Slip what to do??? [Re: Nick1994]
Nick1994 Online   content


Registered: 02/19/13
Posts: 1587
Loc: Phoenix, AZ
I just got off the phone with the idiots at GM. The first guy I spoke to had such an accent I couldn't understand him and hung up, and called again. The next guy was obviously Amwrican, but didn't know what gear oil was for, and didn't seem to understand what a differential was. He said he'd call me back after speaking to some team.
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#3142976 - 10/02/13 07:38 PM Re: Gear Oil- GM Limited Slip what to do??? [Re: Nick1994]
stchman Offline


Registered: 09/25/13
Posts: 517
Loc: St. Louis, MO
Originally Posted By: Nick1994
I just got off the phone with the idiots at GM. The first guy I spoke to had such an accent I couldn't understand him and hung up, and called again. The next guy was obviously Amwrican, but didn't know what gear oil was for, and didn't seem to understand what a differential was. He said he'd call me back after speaking to some team.


Did you check to see if you have the RPO code G80?

Go get a differential cover gasket at the auto parts store. An OEM differential gasket is preferable. Don't use RTV and that is a crummy way to do it. My 2002 Ford Explorer Sport Trac I had to make a gasket as Ford had no gasket for the diff.

Go get yourself 3 quarts of Mobil 1 5W30 and fill it up until the fluid runs out of the fill hole.
_________________________
2013 Chevrolet Silverado LTZ 2WD 5.3L
Mobil 1 5W-30
AC Delco PF48

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#3142979 - 10/02/13 07:41 PM Re: Gear Oil- GM Limited Slip what to do??? [Re: Nick1994]
HardbodyLoyalist Offline


Registered: 08/06/04
Posts: 702
Loc: Lower Alabama
Originally Posted By: Nick1994
I just got off the phone with the idiots at GM. The first guy I spoke to had such an accent I couldn't understand him and hung up, and called again. The next guy was obviously Amwrican, but didn't know what gear oil was for, and didn't seem to understand what a differential was. He said he'd call me back after speaking to some team.


You might do better to send an email. It will be presumably forwarded along until someone who can answer the question receives it.
_________________________
1994 Nissan Hardbody -- Mobil 1 HM 5W30
1998 Ford F150 4WD -- Mobil 1 HM 5W30
2009 VW Jetta TDI -- Pentosin SuperPerformance III 5W30

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#3143072 - 10/02/13 08:21 PM Re: Gear Oil- GM Limited Slip what to do??? [Re: Nick1994]
Realtech214 Offline


Registered: 02/01/13
Posts: 635
Loc: Florida
I would use any 80w90 or 75w90 synthetic perferably. I have never used an lsd additive and have had no issues. I have used dino 80w90 and synthetic 75w90 (valvoline) you dont need any lsd adds, just throw some lube in there and youll be fine
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2001 Suburban PYB
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#3143112 - 10/02/13 08:40 PM Re: Gear Oil- GM Limited Slip what to do??? [Re: Nick1994]
DoiInthanon Offline


Registered: 08/15/13
Posts: 247
Loc: Missouri
I have a 1993 C1500 with all wheel drive. The owners manual has a list of the specified fluids on page 7-25. I use today's versions of fluids that were specified twenty years ago. The results have been ok.

1993 model year lists locking differential, but no limited slip differential.
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Respectfully, Jim

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#3143226 - 10/02/13 10:47 PM Re: Gear Oil- GM Limited Slip what to do??? [Re: DoiInthanon]
Nick1994 Online   content


Registered: 02/19/13
Posts: 1587
Loc: Phoenix, AZ
Thanks, but all my owners manual could tell me was how to check the fluid level, and to check the service manual, which I don't have since the truck was bought over 17 years ago, haha. I bought some Mobil 1 75W90 LS Synthetic for $11.49 a quart at O'Reilly's and a gasket, we'll see how she does tomorrow.
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2004 VW Beetle TDI 164k

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#3143380 - 10/03/13 06:38 AM Re: Gear Oil- GM Limited Slip what to do??? [Re: Nick1994]
NHHEMI Offline


Registered: 07/06/07
Posts: 5263
Loc: NH
As you have been told look for the G80 code on the RPO sticker. If it has G80 you are going to be fine with any gear oil with LSD additive in it.
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