G80

Guys that have the G80 factory posi-trac unit, how do you like it and also what size is your diff. and carrier? i have a 14 bolt diff and 9.5" carrier and i hafta say i think the G80 is great, for a factory extra. where as compared to a after market locker like detroit or auburn its not even close. i rarely ever notice its even there is 2wd, even on wet roads it rarely ever kicks in, i judge this cuz if i floor ot on a wet road i still go straight and if both wheels were to spin you would go sideways a lil. Every now and then when i power brake it will kick in after i let off the brake, prolly the long 2-wheel patch was maybe like 25 feet or something like that. However when in 4-lo, both rear wheels spin ALWAYS. I guess this is cuz of lower rpm's and it engauges easier. I think all in all it is a good thing by GM but they could make some improvements so it performs better in 2wd.

The G-80 locker actually works as an open diff until there is a difference of about 200 rpm and then a weight slides up a ramp a locks it. They are only designed to work a slow speeds and once speed is increased it will automatically unlock. I am not sure of the actual speed it will unlock, But I think it is in the 30-40 mph range. If you stomp on it and get the wheels spinner fast it will only power one wheel and that is why they don't use that in the camaros and such. It is strickly designed for low speed operation. The limited slip in a camaro will power both rear wheels until the cows come home unless there is a difference in traction between the two wheels. I have had the limited slip and the down fall with that in a truck was it acted exactly the opposite of what I needed. If one wheel was in snow and one on concrete the power went to the wheel that slipped making it useless. At first I thought it was faulty, But Auburn said that is how it is supposed to work and it wasn't made for off-road. The G-80 is just the opposite and works at low speed and will lock the rear wheels when the difference in rpm happens and will not unlock unless the speed is increased past a certain point or the wheels are slowed down without power to them. This is why the G-80 locking diff is what they use in trucks and a limited slip is what they use in performance cars. Their are different types of aftermarket lockers that are always locked unless cornering, But the G-80 evn though it is a locking diff and not a limited slip does not work that way.I wish my 14 bolt had the G-80, But mine is the open diff.

Yeh i dunno what to call it, limited slip, posi-trac, or locking diff, i have been told it was all three. By my best account i belive it locks the rear in 4lo cuz when im in 4lo the rear two wheels constantly spin and the front two will alternate from side to side. so more or less it doesnt do too much during normal driving conditions but i am very pleased with it for off road use.

Yeh i dunno what to call it, limited slip, posi-trac, or locking diff, i have been told it was all three. By my best account i belive it locks the rear in 4lo cuz when im in 4lo the rear two wheels constantly spin and the front two will alternate from side to side. so more or less it doesnt do too much during normal driving conditions but i am very pleased with it for off road use.


In so many words that is what I was trying to say. They are more suited for slow or off road conditions and actually will unlock at higher wheel speed. It should perform alright in adverse conditions such as snow or ice, But is not designed for perforfance applications. As I said before I wish I had the G-80 in my 98. I was going to install a lock-rite, But the drivetrain shop told me they are hard on the side gears and that I should change the whole carrier. I am not ready to spend $ 600-800.00 just to have a locking diff. It sounds like yours is doing what it is supposed to.

Well, they are not very good for off-road use. I'll look for some pics, but they like to explode very easily. I would never go off of pavement with a G80...which is a type of limited slip...not posi and certainly not a locker.

interesting, i love mine and it is certainly far better than w/o. i have never seen any posts on this forum concerning a faulty G80. how can you claim it isnt not good for off road use? isnt 3 wheels spinning at once better than just 2?

Well, they are not very good for off-road use. I'll look for some pics, but they like to explode very easily. I would never go off of pavement with a G80...which is a type of limited slip...not posi and certainly not a locker.

They are not made for hard off road use and they do explode in some situations. The G-80 in the C/K trucks is not a limited slip it is a locking diff. It is not a true locker like a detroit or something because they have both rear wheels locked all the time and one will over-run the other in order to make a turn. Most limited slips will act just like a locker on straight run with both tires getting equal traction, However if one wheel hits ice or gravel it will act like an open diff and transfer the power to the slipping wheel. I can't say that for all , But that is how Auburn work. The G-80 acts just like an open diff until there is a difference of about 200 rpm and then it locks just like a tru locker until the power is let off or the vehicle speed reaches somewhere in the neighborhood of 35 mph and then it unlocks no matter what. The G-80 is strictly a low speed locking diff that is not meant for performance applications because even though it will lock when you start to do a burn out after one tire starts to spin it will not stay locked if wheel spin is increased above the certain speed. They can and do grenade when they are abused hard. When used as intended and maintained they hold up pretty well. If you do hard off roading it is hard on it and if you mud bog it won't perform well because it does not stay locked when wheel speed is increased as it is when mudding. All in all it is not a bad diff. It is better than an open diff, But not worth paying to add later. It is a locking diff, Not a locker or a limited slip.

Thunderbolt, I too wished my 92 truck had it. My dad's 91 does, and it does exactly what its supposed to do (just like your post): at low speeds, when one tire slips, they both lock in, and you quit spinning, lol.

His truck goes up blacktopped hills (or any kind for that matter) in wet conditions 10 times better then mine. Basically, you have to feather the gas in my truck to keep it from spinning, and never have to lift or increase the throttle in his to keep it going.

So yeah, I'm with you and Silverado Brethern and like the G80 diff. Its worth checking the option box on if you were in the market for a new GM truck.

yes, they may be good while they work, but all I was saying is that when they decide to go south...you'll wish you never had it.

Yes it is better to have 3 wheels spinning off road than just having 2...but, If your truck has ANY torque, it will either not hold, or explode taking out the ring, pinion, etc.

Silverado Brethern, just do a search on it. Head over to pirate4x4 (which is an awesome 4x4 site) and search there. There is plenty to learn about the G80 rear end that you do not seem to know.

And yes thinderbolt, I said it was like a limited slip without even thinking before I wrote that. My bad...it is a type of "locking differential", but not a locker or limited slip or posi.

yes, they may be good while they work, but all I was saying is that when they decide to go south...you'll wish you never had it.

Yes it is better to have 3 wheels spinning off road than just having 2...but, If your truck has ANY torque, it will either not hold, or explode taking out the ring, pinion, etc.

Silverado Brethern, just do a search on it. Head over to pirate4x4 (which is an awesome 4x4 site) and search there. There is plenty to learn about the G80 rear end that you do not seem to know.

And yes thinderbolt, I said it was like a limited slip without even thinking before I wrote that. My bad...it is a type of "locking differential", but not a locker or limited slip or posi.


I agree with you 100% !! When they go south they literally grenade inside the housing. It would definately not be something I would add after the fact, But if I was buying a new truck I would definately want it.
I also would say they don't stand up to a lot of abuse either, But for the average joe are fine if maintained.

Ok man i believe there may be several cases where they do break but im sure it's a relatively low percentage, for that matter any and everything can go bad with time combined will hard use. I have 114K miles and i run the shit out of this truck on the road and beat around in it off road and i have yet to notice anything faulty.