G80 locking diff

tryn2lrn · June 28, 2004

I seem to get different answers to this, what is the difference between the standard "limited slip differential" and the "G80 locking differential"? I thought the standard limited slip used clutch type packs to "lock" and that's why you had to use the "tranny" type fluid in it. I also thought the the "locking diff" used gears to "lock" and that's why it used standard gear oil. If I am mistaken please set me straight. Thanks

snoman · June 28, 2004

The G80 Gov lock uses clutches that are engaged by a govener when a axle speed differental of about 20rpm is detected and when speed exceeds 20mph it is not allowed to operate anymore. A mechanical locker like a Detroit Locker has no differential and is eithe 2 wheel same speed or 1 wheel "drives" while the other rachets "free" in turns under no or very low power. The G80 is not realy a locking differential, it is a LSD and is wrongly named actually.

tryn2lrn · June 28, 2004

Okay I got that, then what is the difference between the standard LSD and the G80? The standard LSD uses special fluid and the G80 uses gear oil? Thanks

robsawatsky · June 29, 2004

I would have to disagree that the G80 is not a locking differential, it operates very differently from a pre-load, clutch-pack type limited slip.

The G80 operates either as an open or a fully locked differential. Where it differs from many aftermarket lockers favoured by off-roaders is the way the locking mechanism works. Centrifugal force acts upon both a governor and ratchet mechanism to limit operation to speeds below about 20 MPH and at an RPM difference between rear wheels of about 100 RPM. The force causes a cam plate to compress the clutches, which then locks the two axle halves together.

A limited-slip differential uses pre-loaded clutch packs on each side gear. The packs are designed so that higher input torque will clamp the packs tighter and prevent wheel spin.

The operational difference is that the G80 locker grabs more securely but only after wheelspin occurs. The LSD has some grab always that increases as torque is applied to prevent wheelspin in the first place. The G80 will work better when in very low traction conditions as it doesn't depend on torque to get both wheels to spin. The LSD works better on high performance cars on street conditions to prevent loss of traction due to heavy throttle (i.e. 1 tire burnout).

The G80 in GMs comes with a synthetic gear lube that doesn't need a friction modifier additive. It also isn't necessary because the clutches are normally engaged at all under normal traction conditions. The LSD requires a friction modifier for smoother operation, particularly under cornering since the clutches always have some force applied.

tryn2lrn · June 29, 2004

Thanks for the lesson. I did not realize that my rear has synthetic in it from the factory. The owners manual really didn't say anything about (unless I missed it which is possible) that other than giving an oil weight and a gm part number.

snoman · June 29, 2004

I would have to disagree that the G80 is not a locking differential, it operates very differently from a pre-load, clutch-pack type limited slip.

The G80 operates either as an open or a fully locked differential. Where it differs from many aftermarket lockers favoured by off-roaders is the way the locking mechanism works. Centrifugal force acts upon both a governor and ratchet mechanism to limit operation to speeds below about 20 MPH and at an RPM difference between rear wheels of about 100 RPM. The force causes a cam plate to compress the clutches, which then locks the two axle halves together.

The axles never "Lock", it is not a locker. Locker have a mechancal tooth or cogged contection that cannot slip. It has a name wrongly applied and no clutch based diff is a locker, The G80 gov loc is a LSD diff with a govenor controlling its action. LSD's come a couple of different ways and some are preloaded and some are not. The spicer Power Lock tightens it grip with the more torque applied to it and it one of the best clutch based LSD out there. True Trac uses a clutchless worm gear differentail that has no clucthes to wear out and has a torque bias of about 3.5 to 1 (it can put about 3.5 times the torque on grabing wheel than the slipping one and is very smooth in operation and the government uses them in Humvees because they are so reliable and predictable). There is the Eaton LSD (which I believe GM now uses instead of the gov loc) which is preloaded and torque driven as well and a good solid unit that is fully rebuildable. There is the Auburn which uses friction cones the ride in differentail housing to limit slip and is torque sensitive too. But all of these including the gov loc are LSD units.

Mort · June 29, 2004

According to the Eaton website the G80 does indeed achieve full lock and is therefore is locking diff.

Quote:

A Quick Look At How It Works...

We'll start by pointing out that the Locker is a speed sensitive design. That is, it reacts to wheel slip by sensing when one wheel is spinning substantially faster than the other.

So, when you're cruising along on clean dry pavement, the locker operates like any regular open differential.

But, as soon as wheel slip happens, going forward or reverse, the locker immediately kicks in. Here's how.

The differential is set up with a flyweight governor that responds to differences in wheel speeds, and disc packs that are mounted between the side gear and the case.

Whenever one wheel is spinning substantially faster than the other, the governor spins rapidly, causing the flyweight to open. That flyweight then catches on a latching bracket and the lockup process begins.

During lockup, a self-energized clutch system causes a cam plate to ramp against a side gear. This ramping action compresses those disc packs mentioned earlier. The ramping continues until both axles - and therefore both wheels - are spinning at the same speed. This is full lock, and it prevents any further wheel slip. (Note: Axle lockup can only occur at speeds below 20 mph.)

The entire lockup process takes about a split second, and is virtually unnoticeable by the average driver. When both wheels regain traction, unlocking occurs and things go back to normal.

robsawatsky · June 29, 2004

Last chance:

Lock - both axles forced to rotate at same speed, same torque applied to both wheels. How it is achieved is irrelevant.

LSD - Limited slip - get it? Slip is limited not eliminated.

If you want to argue about how a clutch can't lock I expect you don't believe a manual transmission actually locks the transmission to the crank either.

tryn2lrn · June 30, 2004

This is why I love this place I get to learn good stuff every day! Thanks all!

snoman · June 30, 2004

Last chance:

Lock - both axles forced to rotate at same speed, same torque applied to both wheels. How it is achieved is irrelevant.

LSD - Limited slip - get it? Slip is limited not eliminated.

If you want to argue about how a clutch can't lock I expect you don't believe a manual transmission actually locks the transmission to the crank either.

A locker means it CANNOT slip and clutches do slip so a G80 is not a locker no matter what web site says. Call it a LSD or a Posi Trac unit or what ever but it IS NOT a locker and never will be and can only get as tight as clutches let. If you jack on wheel on the ground and restrain vehical (I know this is extreme) with a G80 and stay in it for a while with enough power to spin the grounded tire slowly and the clutches will heat from slipage and the unit will fail in a minute or two tops and be toast. Do this with a true locker and the tire on the ground will burn up and fail long before a true locker even thinks about failing. End of story.

AlanTDickey · July 1, 2004

I agree with robsawatsky. If it locks, it locks - no matter how it does so - whether by compression or teeth. Locking, even by clutches, is not limited slipping.

I cannot find it any more, but I saw on the web a comparison of the F-250, Ram, and a 2500 GM where all three were driven forward with only one back wheel going up a steep inclined ramp. The Goat and F*rd with LSDs reached a stopping point when the ramped tire stopped receiving power as the tire on the ground smoked. The GM (with the G80) went on forward after an initial slip.

snoman · July 1, 2004

I agree with robsawatsky. If it locks, it locks - no matter how it does so - whether by compression or teeth. Locking, even by clutches, is not limited slipping.
I cannot find it any more, but I saw on the web a comparison of the F-250, Ram, and a 2500 GM where all three were driven forward with only one back wheel going up a steep inclined ramp. The Goat and F*rd with LSDs reached a stopping point when the ramped tire stopped receiving power as the tire on the ground smoked. The GM (with the G80) went on forward after an initial slip.

Clutched differentails are NOT Lockers anyway you cut it. Take your "locker"' and smoke one tire slowy for a few minutes and watch it toast. I Dana Power Lock LSD would do the same tire trick and probally last longer in smoke test too. ALL CLUTCHED DIFF's SLIP SOME, it is the nature if the beast. Call it a locker if it makes you feel good but it does not make it a locker because a locker could tire after tire with the other wheel airborne and never miss a beat as any true locker should perform. A G80 with be toast in a just a few minutes at most.

Tree_Hugger · July 2, 2004

I agree with robsawatsky. If it locks, it locks - no matter how it does so - whether by compression or teeth. Locking, even by clutches, is not limited slipping.
I cannot find it any more, but I saw on the web a comparison of the F-250, Ram, and a 2500 GM where all three were driven forward with only one back wheel going up a steep inclined ramp. The Goat and F*rd with LSDs reached a stopping point when the ramped tire stopped receiving power as the tire on the ground smoked. The GM (with the G80) went on forward after an initial slip.

Clutched differentails are NOT Lockers anyway you cut it. Take your "locker"' and smoke one tire slowy for a few minutes and watch it toast. I Dana Power Lock LSD would do the same tire trick and probally last longer in smoke test too. ALL CLUTCHED DIFF's SLIP SOME, it is the nature if the beast. Call it a locker if it makes you feel good but it does not make it a locker because a locker could tire after tire with the other wheel airborne and never miss a beat as any true locker should perform. A G80 with be toast in a just a few minutes at most.

Not only wrong, but stubbornly wrong.

Because the G80 is a speed-sensing , rather than a torque sensing, automatic locker, it needs to use clutches to re-synchronize the axles during the process of engaging the locking gears.

Just because clutches are used to re-synch the speed before locking, doesn't mean they constitute the locking mechanism.

The G80 is a full locker, and IMHO the best automatic locker for road and occasional offroad use.

citydriver · July 2, 2004

Tree_Hugger

jettech · July 2, 2004

I agree with robsawatsky. If it locks, it locks - no matter how it does so - whether by compression or teeth. Locking, even by clutches, is not limited slipping.
I cannot find it any more, but I saw on the web a comparison of the F-250, Ram, and a 2500 GM where all three were driven forward with only one back wheel going up a steep inclined ramp. The Goat and F*rd with LSDs reached a stopping point when the ramped tire stopped receiving power as the tire on the ground smoked. The GM (with the G80) went on forward after an initial slip.

Clutched differentails are NOT Lockers anyway you cut it. Take your "locker"' and smoke one tire slowy for a few minutes and watch it toast. I Dana Power Lock LSD would do the same tire trick and probally last longer in smoke test too. ALL CLUTCHED DIFF's SLIP SOME, it is the nature if the beast. Call it a locker if it makes you feel good but it does not make it a locker because a locker could tire after tire with the other wheel airborne and never miss a beat as any true locker should perform. A G80 with be toast in a just a few minutes at most.

Not only wrong, but stubbornly wrong.

Because the G80 is a speed-sensing , rather than a torque sensing, automatic locker, it needs to use clutches to re-synchronize the axles during the process of engaging the locking gears.

Just because clutches are used to re-synch the speed before locking, doesn't mean they constitute the locking mechanism.

The G80 is a full locker, and IMHO the best automatic locker for road and occasional offroad use.

I'm with Tree Hugger on this,I understand that the clutches are used in "Transition" from free to lock.