GMCtrk

iTrader: (27)

I believe my G80 is still functioning as far as I know, but last winter the G80 was acting up. For some reason it wasn't unlocking on turns (and for that matter I don't even know why it was locked up in the first place). This was in the winter when it was pretty cold outside. The G80 wouldn't unlock and the rear end would bounce It hasn't done it since and is working 100% as far as I can tell. The rear end fluid has never been changed (144k miles). Is this a case of maybe the rear end fluid not doing it's job in the cold or is the G80 on it's way out? The reason I ask is I'm about to swap 4.10s in place of the 3.42s and I'm debating on whether to get a TruTrac or not. Thanks

PathfinderJr

iTrader: (6)

the G80 is mechanically operated, so I don't know why any break down of fluid should affect its (weak) performance. I'd go ahead and swap it out to an after-market diff just for peace of mind.

My dad's stopped working recently, and he found out the hard way when he lifted a rear wheel. Luckily it only just broke instead of taking out the whole rear end. The one in my truck likes to make loud bangs sometimes, so I can't wait to get it out of there.

budhayes3

iTrader: (19)

Since the fluid lubricates the mechanical unit, I think it may play a part in the G80's operation...I did a fluid change once, and afterwards my rear was locked temporarily, for whatever reason. I think it had something to with the fact that I cleaned down the housing with brakleen and the locking mechanism may have gotten some brakleen on it and gone dry? After a few turns it unlocked and now operates as it should. I no longer clean the rear when I do fluid changes, just drain and fill.

With a 144k though, your G80 may be on it's way out...a Detroit TrueTrak would be my suggestion...especially after your recent engine swap

MonteCarlo31

yes but I believe there is something to do with the fluid as you are must used Limited slip additive or GM / Royal Purple w/ the blend already in it for the right friction properties.

PathfinderJr

iTrader: (6)

eh, I guess it makes sense. I just was thinking more along the lines of clutch-type units needing the friction modifier additive and such. Nevermind me then! haha...

1989k1500

iTrader: (23)

g80 does have clutches.

NegraRCSB2X4auto

iTrader: (15)

swap it now and save your self the money when it goes out later.

PathfinderJr

iTrader: (6)

the youtube video i saw of the g80 showed only a mechanical activation. there was a little lever with weights on it and stuff, hence why it disengages past 25mph, or whatever the speed is.

dlstewart01

GM says NO additive for the G-80. They do come from the factory with synthetic fluid however. It is a mechanical locker. It does not have fiber disk like a limited slip which needs the friction modifier.

All trucks have the option of a G-80 gov lock made by Eaton, with the exception of quadasteer which was available with a G-86 limited slip.

Have a good one,

Don

krambo

iTrader: (4)

I opted for no additive as well. Just Mobil synthetic gear lube.