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Blown rear G80 diff?

24K views 14 replies 8 participants last post by  jocko463 
#1 ·
Hey new user to this site :) have an issue with my truck . the rear posi locker wont engage no more.... its like a 1 wheel peel. im new to these diffs and dont know anything about them , can some one help me out and what can i do to fix it? it drives like normal too . no noises..... :(

thanks steph
 
#2 ·
Let's make sure you have the G80 first, and then go from there. Some GM trucks don't have the locking rear diff. Open the glove box, and you should see a bunch of codes. Look for "G80".

One easy test is to take the rear cover off the diff, and see how things look. If there is a problem, you should see broken parts or shavings in the fluid.
 
#3 ·
yea it has the g0 for sure , i check and plus when i would go slow you'd hear it lock up . now its one wheel peel. i hate it.... its a huge noticement.., im planing on checking it out sunday or tomarrow, my buddy has a spare used g80... and we should go from there. would it be better if i did the g80 mod to the locker so it stayed engaged at higher speeds soo it does lock,unlock,lock,unlock in snow when accelrating..
 
#4 ·
OK. Have you taken off the rear cover? Doing that will tell you what's wrong with it.
 
#8 ·
I've heard that the G80 were like ticking time bombs. It was never a matter of "IF" the differential goes out, it's more of a matter of "WHEN" it goes out. So i've heard...
 
#11 ·
would it be better if i did the g80 mod to the locker so it stayed engaged at higher speeds soo it does lock,unlock,lock,unlock in snow when accelrating..
You don't want that. That can be hard to control and too much gas at the wrong time and the rear end will pass you up. That's precisely why they are designed to disengage at around 20 mph, safety.

Has anyone changed the gear lube and used a Limited Slip Additive in it? Limited slip additives can damage a G80 locker.

Like anything, the G80 can be abused and neglected and blamed for things that are not its fault.
 
#12 ·
I agree with you all, anything that is abused will most certainly give you trouble. But from what i've read on other forums like Full Size Chevy and GM-Trucks, the G80 has given some truck owners problems in the past! Some have even dubbed it with the name "Gov-Bomb". But like I stated, this is what i've heard...
 
#13 ·
the only bad thing ive heard about it was from the rock crawling guys but the rocks they were climbing required an air locker so i say the g80 is a great diff.
 
#14 ·
The G80s on the 1/2 tons are indeed very temperamental and will not hold up to abuse or "peeling out" all the time. This is a very common issue on the GMT-800s and I am one of the unfortunate ones who had the G80 go out on me on my first truck, a 1999 Silverado 1500 with about 80,000 miles on it at the time. I got the truck used so I'm assuming the previous owner was not too nice to it as I drove it like a grandma, most of the time. The differential shop that did the rebuild said they see on average about 4-7 come in a week with the same problem. This was back in 2004. I had also had a rear end diff service done at about 70,000 miles and no issues were detected at that time. I've seen many posts over on gm-trucks.com over the years of folks who had the same issues.
 
#15 ·
There is a big difference between the G80 locking rear differential and a true posi-traction differential.

The G80 is for low speed engagement; think trying to haul the bass boat out of the lake up the slippery ramp. This is where the locking mechanism of the G80 engages. The mechanics of the design will only allow the differential to lock up at low speeds (like below 10mph) and release at higher speeds. The system senses how fast the differential is turning and if it is spinning too fast it won't engage so, no , you're not going to be doing any "posi burnouts" in your truck with this system. If you really want to see how it works, type "eaton g80 locking differential" in your fave search engine. Here's one of the YouTube vids that you'll find :



There is no requirement for any special lubricant for the axle. And you won't be feeling any of the ratcheting or noise that a posi-traction axle makes because the differential is not locked permanently. Except for the conditions where it will lock, the G80 operates as an open differential.

The way to test your G80 is to put your truck in a situation like the video ...one wheel on a slick surface. Then slowly begin to accelerate and don't just tromp the gas pedal because the G80 won't engage ...just take it slow, the slick wheel will spin a bit then the G80 will lock both axles and you'll move out.

I have this option on my truck (by the previous owner) and it does work pretty slick.

Mike
 
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