G80 Posi rear ?

[Twistin6]

Do these things go bad gradually or is a device that either works or it doesn't? Curious that if the more power that is throwed at it if it would tend to go one legged if it was failing vs. seeming normal at a lighter load.

This is in relation to another thread I posted concerning MT ET Street drag radials in another section. After talking to a few spectaters they all swear just the passenger side was smoking the tire hence my hooking up issue. I know for a fact and it has been fairly recent that both tires would lay it down. Haven't pulled out on the street to see if two parellel marks appear yet and would like o refrain from that if possible.

 

[novaderrik]

the clutches can wear out and cause it to act like an open diff under power.

 

[Black Car]

When was the last time the rear end fluid was changed?
Be sure to use the GM postive fluid (small bottle) in with the gear oil.

Gary

 

[Twistin6]

As for the last change on rear end oil I can't answer that. I just know that I have not done it in a year of ownership. Is the a small rebuild or clutch kit that can be picked up at the dealer? And if so is set up required with shims and backlash adjustment? Or is a straight bolt in type thing? Thanks for all the help

 

[pacecarta]

if its a gm posi carrier unit its rebuildable , not sure on clutches as last i heard they were approx $114.00 and now discontinued
if you have the gm unit and clutches it can be done in car with out messing with backlash , even if you decided to pull the carrier it still wouldn't require any more than replacing the side shims and caps exactly where they were before removal

if someone put an auburn in there you're SOL unless the unit is under 5years old , if it is under 5yrs old (they are date stamped and i think you need the receipt) the rebuild is doable for a fee aprroximately same as GM clutches , if not its almost cheaper to buy a new unit if sticking with the auburn .

 

[Black Car]

FWIW, I would drop the cover and look and see what you have in there. See other post....
Something could be damaged or broken.
If it looks good then I would replace the fluid and put a bottle of the GM lube in it.
The previous person may NOT have added the GM positive fluid and this will cause the rear end to act like a peg leg. When turing and accelerating cause the rear end to grab and then release and grab again.

Again just my $0.01.
Gary

 

[Twistin6]

FWIW, I would drop the cover and look and see what you have in there. See other post....
Something could be damaged or broken.
If it looks good then I would replace the fluid and put a bottle of the GM lube in it.
The previous person may NOT have added the GM positive fluid and this will cause the rear end to act like a peg leg. When turing and accelerating cause the rear end to grab and then release and grab again.

Again just my $0.01.
Gary

Interesting you mention grabbing and releasing it is an audible grind momentarily? Or would it go unoticeable to the driver pulling out making a turn for instance?

As for it being a GM posi I believe it to be....If I were to pull the cover and check what are the tell tell signs of a GM unit over another?

 

[Black Car]

You will feel it. No noise, but it reminds me of a crab walking.

Jack up the rear of the car with both wheels off the ground.
Put tranny in netural, rotate one wheel, if the other wheel rotates the same direction, then it is a limit slip unit.
Let one side of the car down-one wheel down with weight on it.
Use a torque wrench on the other wheel (in the air) lug and see how much torque it takes to make the wheel rotate. I forgot the exact number but if under 50#/in then your clutches (if G80) needs replacing.

The GN/T-Type has pictures of what the G80 looks like. I don't have a link for you. Sorry.

When you pull the cover take a picture of what you see and post it here.

Gary

 

[Twistin6]

Thanks for your help....The trunk label says G80. So until I pull the cover and investigate I have to assume that it still is. I was curious of obvious differences in a GM unit that I believe I have vs say an auburn unit. Because I know it is a posi and acted as such before. I will look for the pic you mentioned and compare when I get into it.

 

[novaderrik]

the stock eaton posi has a spring in between the spider gears and you can see clutch packs in behind the spider gears, and a locker or Auburn doesn't have that stuff.
just go to Summit/jegs/wherever and look at pics of different differentials.

 

[Twistin6]

I went ahead and purchased the clutch kit for the G80 rear at a local GM dealer. The spring is seperate and got that as well. Parts should be here next Tuesday. At that time I will pull the cover and have a look. I may not need the parts yet but figured I would order them while still available from the dealer.

If needed is it a very involved install? Do I need to pull the axels to do it or can I do it all through the punkin cover? Anyone whom has done this I would like to hear any tips and maybe a hit the high points of installation.

Thanks