81 replies to this topic

[Mr. P.]

There is no mention of care and feeding for the rear axle in the Silverado SS owner's manual, so after a bit of research here it is. I have tried to make this as concise as possible but bear with me

The Silverado SS is equipped with the Eaton G80 rear differential, a mechanical-locking limited-slip unit. Production tolerances in this axle are very tight, and the clutch pack and seals are specifically designed for use with synthetic gear lube. The axle is filled at the factory with a synthetic GL-5 75W-90 fluid made by Texaco (part #2276) and resold at the GM parts counter as service #12378261 for about $25-30/qt Using mineral based gear lube in this differential will cause errant 'slip-stick' operation in the clutch pack, and if not corrected (by using synthetic fluid) will lead to shuddering around corners and clutch pack failure.

During the first 300-500 miles of life the G80 rear axle develops very high temperatures as the ring and pinion break in (over 350-degrees); also, any dust or casting debris from manufacture will be washed down into the fluid. In these first miles of life avoid towing, high loads, and high-speed extended driving until the ring and pinion have seated and rear axle temps fall to normal. Due to this high initial break-in heat a gear lube change is in order because additives are replenished and contaminants are eliminated (this quoted directly from Eaton). Draining and refilling with synthetic fluid after this initial break-in can be considered 'lube for life' but most conservative mechanics recommend draining and refilling at 40K to 50K intervals, even earlier in dedicated tow/severe duty vehicles.

Failing to drain and refill your rear axle after break-in can result in high noise operation, howling, and/or outright bearing failure as (1) the debris from manufacturing continues to circulate inside the axle housing and tears up bearings and seals, and (2) the lubricity of the factory filled synthetic gear lube is greatly compromised by break-in heat.

Draining and refilling your rear axle gear lube is easy for the novice mechanic, and most non-mechanics can perform this basic service with a little step-by-step guidance. To begin just review this how-to, buy the required gear lube at the local auto parts store, park your truck on a level surface, and start wrenching.











(continued...)

Edited by Mr. P., 18 August 2008 - 01:22 PM.

[04CHASE]

sorry but i had to. ,Good post though i think this will help a few of us.

Edited by 04CHASE, 23 August 2005 - 02:07 AM.

[Mr. P.]

(...part II)











After collecting your tools take your SS to a convenient parking lot and drive in lock-to-lock figure-8s at a comfortable clip (not insane), ten laps ought to do; the figure-8s are good for getting the clutch packs saturated in gear lube, remove varnish build-up from the clutch faces, and sling oil out to the wheel bearings. Finally, after a 15-minute rest check for leaks and lowered fluid level (it may have dropped as much as 1/4-qt, or maybe not).

Regardless of the service interval you choose (40K, 50K, or none at all) check at every oil change for leaks and pull the fill plug every 7500 miles to top-off the rear axle fluid.

Mr. P.

Edited by Mr. P., 18 August 2008 - 01:30 PM.

[kaotik1]

Awesome post, for those who don't know how to do this. On a side note should you break the gasket, "the right stuff" works great for making a new gasket versus using RTV.

[smithl3]

Welp, you did it again, nice work on the HOW-TO misterp.

Or should we drop the "p" since Diddy did and just call you mister??

Just a thought ;)

[BILLS04SS]

Excellent post MisterP... Excellent step by step.. I'm gonna do that this weekend. Since I'm not sure its ever been done on my truck..

Edited by BILLS04SS, 23 August 2005 - 12:10 PM.

[Mr. P.]

Excellent post MisterP...     Excellent step by step..   I'm gonna do that this weekend.  Since I'm not sure its ever been done on my truck..  

Thanks for the compliment - Yeah that's exactly why I did mine, I suspect my rear diff is running a little loud, and I'd bet this was not done by the original owner and I wanted to see if doing this would possibly quiet it down; with everyone's front and rear diffs dropping like flies from bearing failures it seems necessary IMO.

Mr. P.

Edited by misterp, 23 August 2005 - 02:20 PM.

[zippy]

according to our information the limited slip additive is a no-no in gov-lock type differentials...

[fox_forma]

do we have to worry about about breaking that fill plug when trying to break it loose? I planned on changing my oil this weekend so I might as well do this as well. Good Post

[Mr. P.]

according to our information the limited slip additive is a no-no in gov-lock type differentials...

Well please set me straight here, is it damaging or just a waste of money? I'll edit the how-to on that.

Mr. P.

[Mr. P.]

do we have to worry about about breaking that fill plug when trying to break it loose?  I planned on changing my oil this weekend so I might as well do this as well.  Good Post

Use a high-quality extension; if you use a cheap one (soft metal) then you may round-off the end of the extension as well as round-out the fill plug. Make sure that you keep the tool square to the plug. In some cases a 1/2" breaker bar with 1/2" to 3/8" step-down adapter might be needed.

[SSplaytoy]

I have a semi dark ring around my rear differential now, but I didnt do the oil nor have a leak. What's the deal?

Good how to though.

And we all know that the pink shop towel doesnt make you any less of a man ;)

[tawss04]

Guess you did not notice the drain plug on the bottom of the diff for easier fluid draining. Good instructional though.

[Mr. P.]

I have a semi dark ring around my rear differential now, but I didnt do the oil nor have a leak. What's the deal?

Good how to though.

And we all know that the pink shop towel doesnt make you any less of a man  ;)

Real men have a pink toothbrush.

[Mr. P.]

Guess you did not notice the drain plug on the bottom of the diff for easier fluid draining. Good instructional though.

Thank you for the compliment; you'll have to post up a photo for others to see; the axle in my SS does not have a lower drain plug even though there is pad cast for it.

Mr. P.