Rear axle question - G80, 4:10

[Biggun]

Well, two, actually--

• 1998 Silverado 4X4 1-ton Crew Cab---I've got a whine (only when accelerating) coming from somewhere that starts in at about 50 MPH, and disappears somewhere between 55 and 60 MPH. It's not real loud, but it's there. I sorta figured being a 1-ton truck that maybe the gears are cut straighter, thus the noise (?) I don't *think* anyone has messed with the rear-end, so poor gear alignment/loading isn't the first thing I would suspect...but I can't say for sure. I can't imagine that the ring and pinion are worn out, as the truck only has 118k miles on it. The diff DOES have oil in it, which brings me to my second question:
• My axle code indicates that the gearset is a limited-slip positraction, if I'm translating it correctly. The capacities and lubrication chart in the manual just calls for regular 80-90 GL-5 gear oil and doesn't mention anything about a limited slip additive. I thought all limited slip axles needed a friction modifier (???)

Sage wisdom appreciated.
Thanks!

 

[454cid]

It's a locker, not a limited slip. I believe that cars use the same RPO, but in that case it's limited slip.

You don't want an additive, as it can mess with the locker, locking up. GM actually had a TSB out on it because it was a problem with people putting additives in.

GM switched to a synthetic gear lube in the first half of 99, which is something like a 75w90.... but it costs more and is harder to find. my truck may have had it, but I'm just running plain old dinosaur 80w-90.

 

[df2x4]

I'm not much help on the first question, sorry. I can answer the gear oil question though. The G80 locker carriers are Eaton Gov-Locks, and they will not operate properly if you use any kind of friction modifier. There is a TSB from GM about this.

https://www.chevytalk.org/fusionbb/showtopic.php?tid/256237

You need a GL5 rated 80W-90 with no friction modifier or additive. I use this in both of my '97s, ACDelco 10-4051.

https://www.amazon.com/gp/product/B007Q10F3S

 

[Biggun]

Thanks!
Sounds like I haven't screwed anything up...yet...

 

[stutaeng]

I have an almost identical truck as yours SRW also with 4.10s. Not sure what the whine sound would be. Maybe lift the rear end and hit the gas?

As far as the G80, I thought it was more or less a limited slip. It is not a "locker," at least not a "selectable locker," in the sense that both wheels get locked and spin at the same rate. A locker is activated by a switch

I don't think it would be the rear axle whining, unless maybe someone messed with it...

 

[454cid]

As far as the G80, I thought it was more or less a limited slip. It is not a "locker," at least not a "selectable locker," in the sense that both wheels get locked and spin at the same rate. A locker is activated by a switch.

It's a locker, not a limited slip. Locker does not mean controlled by the driver, that's another feature of lockers like the Ox Locker, or ARB Air Locker. The G80/Eaton locker is either locked or unlocked, there is no in between where it slips.

 

[df2x4]

^ X2. There are standard lockers that engage and disengage automatically, and manually switched lockers. The G80 is a standard locker that engages when it detects a difference in wheel speed at low speeds. It will not engage at all above 20-30MPH or so.

 

[stutaeng]

It's a locker, not a limited slip. Locker does not mean controlled by the driver, that's another feature of lockers like the Ox Locker, or ARB Air Locker. The G80/Eaton locker is either locked or unlocked, there is no in between where it slips.

Oh, ok. Then I hadn't really understood the mechanism of the G80. Somehow in my mind I thought there was slippage from one axle to the other...

 

[1997]

GMT400 stock, G80 is a GOVLOC as stated, which uses clutch plates, in fact I think GM is using the same deal in up to 2018's....
Hence the confusion on if you need to add that special additive.
A true locker doesn't have clutch plates.
The clutch plates are for smoother transition between lockup and when unlocking.

 

[454cid]

GMT400 stock, G80 is a GOVLOC as stated, which uses clutch plates, in fact I think GM is using the same deal in up to 2018's....
Hence the confusion on if you need to add that special additive.
A true locker doesn't have clutch plates.
The clutch plates are for smoother transition between lockup and when unlocking.

They are either locked or unlocked. It is a true locker.