G80 Issue

2005GMCZ71 · June 18, 2008

Hmm, first post is a possible problem, hope not. lol

I recently bought a 2005 Gmc Sierra 1500 Z71, that has the GT5 rear with a G80 locker, and auto 4x4. This truck has 58,768 miles as of right now, and as far as i can tell has never been abused, or even worked hard.I use it as a DD, and for light work( yard, towing small trailer with ATV on it).

The issue i am having as this, Yesterday I was in the back field repairing the fence that border my land, the field is slightly muddy,(nothing that would require locking it ain 4x4), from the rain on monday.I finished up, hopped in and went to take off back to the house, I was greeted with a loud ratcheting sound and a fairly violent shutter, that vibrated the entire truck. I stopped, and got out to check on this, figuring in my hurry, i applied way to much power and broke something(thinking U-joint here). Nothing seen. There were 2 almost equal ruts where both rear tires had spun(locker works lol).

Took off again, same thing. Fearing something major was failing, i put it in nuetral, locked it in 4low, and crawled, slowly back to the house, with no noise, or shutter.

Drove it this morning to work, and it is smooth and quiet.

So i guess my real questions are these:

Does the G80 supposed to be harsh and noisy?

is ths ratcheting sound normal?

Is there a "special" technique to driving with this locker. (ie. apply slight power, let off, then apply power again)?

Am i just unfamilar with this setup, because i applied steady throttle when taking off on slick surface, and have grenaded something?

I am going to do a fluid change on both diffs this weekend, i guess if there are chunks floating around in the rear, i will have my answer to the last question

redvett · June 18, 2008

G80 locking differentials do make a clunking noise when engaging thats normal.

If you change the G80 oil use only the recommended synthetic oil with NO additive.

95Sierra2500 · June 18, 2008

I've heard that lockers can make the noise/feeling you're describing. On harder surfaces, a locker would either peel out or lead to wheel hop, which is the feeling you're describing. Basically the locker felt that one of your wheels was spinning too fast, and engaged the other wheel as well. It SOUNDS like it's working right, but I'll have to have others weigh in on that.

asilverblazer · June 18, 2008

Sounds like it was axle wrap/wheel hop and that the locker was working.

2005GMCZ71 · June 18, 2008

O.K, Thanks guys, that really eases my mind. I should have figured it was fine when i drove it this morning, and it acted normal. Guess i'll really know Saturday when i change fluid

BTW, Is there a special driving technique to maximizing the lockers effectiveness, I mean do you apply gentle power until it locks, then go for it, or is it "hammer down" and let the locker figure it out, and pray it does not grenade?

2000DV4.8 · June 18, 2008

O.K, Thanks guys, that really eases my mind. I should have figured it was fine when i drove it this morning, and it acted normal. Guess i'll really know Saturday when i change fluid

BTW, Is there a special driving technique to maximizing the lockers effectiveness, I mean do you apply gentle power until it locks, then go for it, or is it "hammer down" and let the locker figure it out, and pray it does not grenade?

Well the "G" in "G80" does stand for grenade... Hammer Down isn't the best idea with the G80.

2005GMCZ71 · June 18, 2008

, DV2000NJ,that's what i have read about it, thanks for once again raising my paronia level, j/k.

2000DV4.8 · June 18, 2008

The G80 is fine in a stock truck if you don't do any crazy wheeling with it, they just don't hold up well to... abuse. Just use common sense (don't mash the throttle in snow/mud, don't burn out on dry pavement, no drifting etc.) and you should be fine.

Schmids5.3l · June 18, 2008

Mines held up!! I'm testing it's durability again tomorrow at the track.

If I take really sharp turns, as in U turns, sometimes it will engage and make all kinds of fun noise. 80% of people probably shit their pants when that thing engages.