Need advice rear diff service on my Silverado

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Dallas Texas Area
2005 Silverado Z71
280K miles
RPO GU6 3:42 with G80 limted slip rear diff


Just use it as a basic work truck no hauling. Have no clue on previous maintenance so wanted to get this done


What you guys recommend ?? Book calls for 75W-90, But I have some supertech 80W-90 left at my shop.



So would the 80-90 work okay or go with the 75-90 ??


Dave
 
I would say YES, others may not.
As long as the Super Tech has the LSD additive or you add your own, I think you'll be fine.
 
The additive isn't necessary with the G80. GM actually advises against it.

Either or should be fine, but I'd use what it called for personally. $5 a quart at WM for full syn ST 75w90.
 
I am with the others. You will be fine with what you have on hand, 80W90. But given you will only use a couple of quarts, I would but what is spec'ed for the diff.
 
I would use the best stuff possible since the rear end is one of the weak points in these trucks. They aren't bad, but I've seen a few of them fail at higher mileage.
 
Originally Posted by GMguy84
2005 Silverado Z71
280K miles
RPO GU6 3:42 with G80 limted slip rear diff


Just use it as a basic work truck no hauling. Have no clue on previous maintenance so wanted to get this done


What you guys recommend ?? Book calls for 75W-90, But I have some supertech 80W-90 left at my shop.



So would the 80-90 work okay or go with the 75-90 ??


Dave



Your owners manual calls for synthetic in the rear diff and conventional in the front diff. Is the Supertech 80w-90 Synthetic?

I believe the G-80 is a locking differential, not a limited slip differential and does not require the friction modifier.

Also your owners manual says, if it is a Quadrasteer, do not add friction modifier.
 
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GM trucks DO NOT use a limited Slip Differential (except in the Quadrasteer models - Dana). Its use a Eaton G80 Locking Differential. Additives are not required!!

Quote

¨ Optional Equipment (G80 Order Code) on all GM two-wheel and four-wheel drive light trucks and sport utilities.

Benefits

¨ Improved traction differentiates the vehicle relative to other rear wheel and four-wheel drive vehicles on the market.

¨ Maintenance free; requires no lube additives.

¨ Enhanced towing and off-road performance.

¨ Patented carbon friction disc technology enhances performance and durability while reducing warranty claims.



Principles of Operation

¨ Wheel speed difference (left to right) in excess of 100 RPM will cause a flyweight mechanism to open and catch a latching bracket.

¨ The stopped flyweight will trigger a self-energizing clutch system, which results in the cam plate ramping against a side gear.

¨ Ramping increases until both axles turn at the same speed (full lock), which prevents further wheel slip.

¨ At speeds above 20MPH, the latching bracket swings away from the governor and prevents lockup from occurring.



Technical Specifications

¨ Automatic locking takes place within a fraction of a second, so smoothly that it is unnoticed by the average driver.

¨ Unlocking occurs automatically, once the need for improved traction is gone, and is unnoticeable to the average driver.

¨ Compatible with anti-lock brake systems
 
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Delvac 1 is what I use in AAM's rears with G80's … paid $32/gallon for what's going in the Z71 …
 
Originally Posted by dlundblad
The additive isn't necessary with the G80. GM actually advises against it.

Either or should be fine, but I'd use what it called for personally. $5 a quart at WM for full syn ST 75w90.




Yes, ST WM 75-90 is Full Syn and $5.86+tax down here. But have a Atwoods farm in town with top tier fluids CHEAP , gonna check out today before I pull trigger


DAve
 
You live in Oklahoma . Might go a little thicker ? Best I can tell , it gets about as hot in Oklahoma as it does in our part of Texas .

Does the diff have any clunking or whine ?

How are the wheel and pinion seals ?

Might consider throwing on a diff cover with a drain or fill plug ?
 
80w90 will be fine. Your truck should have the re-usable gasket so it will be easy to change, as long as you can get the fill plug out. Although it should have an iron center section, so the plug should not corrode itself in there.
 
Thanks guys for all your advice, I went ahead and got 3 qts of 75W-90 full syn at Walmart came out to around $20 after tax

75W-90 is easy to find around here, Everywhere else it was 80W-90 or higher


Shouldnt matter that much anyways, In a few months around spring/tax time I plan to sell it since i'm moving back home to Chicago and would need something else drive around there lol


But I like to get TOP dollar on my vehicles at sale time so I prefer to do any basic maintenance and document it to attract more buyers


Dave
 
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Da Bears!
laugh.gif
 
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