G80 vs G86

[dsteelejr]

Everyone seems to have heard of the G80 locking diff. I recently acquired my parent's '73 C20 camper special. The original owner ordered the truck with just about every top-of-the-line option available at the time. The RPO code sheet is still on the fender. I've known since I was a kid the truck had limited slip and now that the truck is mine I was expecting to see G80 locking differential on the RPO code list. Instead it shows G86 limited slip differential. Whats the big difference between the two? Is one stronger or better than the other? It's a 14 bolt FF rear end and has withstood the test of time because it's the original rear end and has never been rebuilt. Still runs good and quiet and the limited slip still works.

 

[75gmck25]

G86 uses clutches to lock the two wheels, while the G80 has a centrifugal locking pawl that engages when one wheel is about 100 rpm different than the other. I didn’t know they used the G86 in HD trucks in that time period.

My guess is that the G86 might engage a little more gradually, but would be subject to wear over time. The G80 is called the gov-bomb because guys spin it up on a hard surface and it really engages with a bang, which can break it.

Bruce

 

[dsteelejr]

The G80 is called the gov-bomb because guys spin it up on a hard surface and it really engages with a bang, which can break it.

If that's true then maybe the G86 is a better option. Less shock load will allow the unit to last longer. Sure, G86 clutches will wear out eventually, but nothing lasts forever.

 

[bigcountry78]

G86 uses clutches to lock the two wheels, while the G80 has a centrifugal locking pawl that engages when one wheel is about 100 rpm different than the other. I didn’t know they used the G86 in HD trucks in that time period.

My guess is that the G86 might engage a little more gradually, but would be subject to wear over time. The G80 is called the gov-bomb because guys spin it up on a hard surface and it really engages with a bang, which can break it.

Bruce

Funny, my truck has the “gov-bomb” and ran 36” tires on heavy steel wheels for 30 years. Still works just fine. It kills me how people will absolutely abuse something way beyond what it was designed to do, and then get mad when it breaks. I’ve had several GM trucks with the g80, all used for hundreds of thousands of miles, and non of them have ever given me problems. Sorry, that’s a bit of a hot button issue with me.

 

[dsteelejr]

Funny, my truck has the “gov-bomb” and ran 36” tires on heavy steel wheels for 30 years. Still works just fine. It kills me how people will absolutely abuse something way beyond what it was designed to do, and then get mad when it breaks. I’ve had several GM trucks with the g80, all used for hundreds of thousands of miles, and non of them have ever given me problems. Sorry, that’s a bit of a hot button issue with me.

When you take care of your **** it'll last a long time.

 

[bucket]

Funny, my truck has the “gov-bomb” and ran 36” tires on heavy steel wheels for 30 years. Still works just fine. It kills me how people will absolutely abuse something way beyond what it was designed to do, and then get mad when it breaks. I’ve had several GM trucks with the g80, all used for hundreds of thousands of miles, and non of them have ever given me problems. Sorry, that’s a bit of a hot button issue with me.

Some last, some don't. I've seen lots of them that 'explode' in stock vehicles and normal driving. Mostly all the 7.5" and 8.5" diffs though. I think what happens is the little fly weight comes loose and it gets wedged between the gears and then kablooey.

On my own personal trucks, I've had one or two that just plain didn't work and that was it. No shrapnel.

 

[bigcountry78]

Some last, some don't. I've seen lots of them that 'explode' in stock vehicles and normal driving. Mostly all the 7.5" and 8.5" diffs though. I think what happens is the little fly weight comes loose and it gets wedged between the gears and then kablooey.

On my own personal trucks, I've had one or two that just plain didn't work and that was it. No shrapnel.

Must be a luck of the draw thing. My 98 was driven pretty hard. But it only had 285’s on it. Still never had any issues. Never had any trouble with hat truck at all actually, other than transmissions. Probably the best truck I’ve ever owned. Still regret selling it.

 

[dsteelejr]

Must be a luck of the draw thing.

Or unluck of the draw.

My parents have had this truck since I was two years old. Theres never been an issue with the G86. Maybe its just a G80 thing.

 

[bucket]

The G80 in the full float 14bolt is supposed to be much more durable compared to the smaller GM axles, I think that's worth mentioning here too.

 

[75gmck25]

Bucket - however the interesting part is the OP apparently has a 14 bolt FF with a G86, not a G80. I didn’t know they made that combination.

Bruce

 

[bucket]

Bucket - however the interesting part is the OP apparently has a 14 bolt FF with a G86, not a G80. I didn’t know they made that combination.

Bruce

I didn't either. Was it maybe leftover from the previous Eaton axles? I know they were similar, internally, to the 14 bolt axle.

 

[Grit dog]

Idk about smaller axles but agree with above. 14 bolt and AAM axles, G80 works as intended, reliably.
The gov bomb argument is akin to Ford and Dodge fans who say GM ifs is weak. Just another baseless argument.

 

[Vbb199]

Idk about smaller axles but agree with above. 14 bolt and AAM axles, G80 works as intended, reliably.
The gov bomb argument is akin to Ford and Dodge fans who say GM ifs is weak. Just another baseless argument.

The newer gm IFS gets it reputation because of the tie rod angle in stock form, which isnt very strong, then you add **** boy tires and wheels, plus a lift, and then boosted launches, which FURTHER compromises the integrity of the TRE angles..... they break... then sister ******' rednecks all around the world spin stupid stories that "all" gm tre's are garbage..... stupid.

 

[Vbb199]

And in reference to the GM 14bff g80 unit, ive already tore mine up in my 14 bolt. Its a 99-06, the gen immediately before the AAM series.

That damage was done on 39.5x15 boggers, with a very docile 4.3 v6 pushing power to the 14 bolt.

The axle itself isnt thrashed i dont think, but something isnt working anymore with the g80 unit, i assume cooked clutches?. I have 1 wheel peel now.

That hunk of ****, like a gm 10 bolt g80, is gonna get tossed eventually for a real traction device.

 

[dsteelejr]

And in reference to the GM 14bff g80 unit, ive already tore mine up in my 14 bolt. Its a 99-06, the gen immediately before the AAM series.

That damage was done on 39.5x15 boggers, with a very docile 4.3 v6 pushing power to the 14 bolt.

The axle itself isnt thrashed i dont think, but something isnt working anymore with the g80 unit, i assume cooked clutches?. I have 1 wheel peel now.

That hunk of ****, like a gm 10 bolt g80, is gonna get tossed eventually for a real traction device.

I talked to my uncle, who is a seasoned retired mechanic, about this issue and he says he's seen so many G80s grenade. He thinks they're junk. Sure, some have lasted a long time, but he's seen too many blow up to have a positive opinion of the G80.