Auto 4wd, Auto Locking Rear Diff, Traction Control, When Do These Turn

newdeal · November 30, 2010

Ok so my truck has auto 4wd, a auto locking rear diff and traction control. I know all of these sense wheel slip and turn on but is there an order to it or do they all just come on at once? Reason I ask is because in my pontiac G6 I could definately hear the ABS kick on when the tires slipped, with the truck I can't hear the ABS come on (in 2wd mode) so I figure either its quieter or the locking rear diff engages before the traction control and so it never slips enough to get it to come on. I was wondering the same for the auto 4wd mode, does it engage at the same slip as the rear diff or does it have to slip a bit more?

uchi · November 30, 2010

well on my 06 i dont have the traction control, but everything comes on pretty much instantly when you start to loose traction. the locker kicks in in 2wd and it gives alot of traction. you really need to be in some standing water to break the rear tires loose i find, and in auto modeyou wont get any traction loss itll just engage the front wheels as soon as you start to break traction and off you go. i havent had a chance to try my truck out in the snow yet as we havent gotten any but they should both come on at about the same time. they both engage as soon as the traction is lost.

ChevyTech77 · November 30, 2010

It all depends on the situation but yes, they are all passive traction control entities that work together to keep

you going in the path that you are intending to go, forward.

tbondu · November 30, 2010

Mine has all of those items as well. When I'm out hunting and the roads are possibly bad (muddy) I turn it to Auto and be sure to turn traction control OFF. If you leave it on and hit mudd it will get confused and try to apply the brakes to slow down the wheel spin (which happens to be every wheel). I found this out the hard way and ended up buried. If you turn it off you can get wheelspin to go through the slop.

The locker does help quite a bit in 2wd as well, which is handy for when your front differential actuator goes bad and it won't go into 4WD while you're stuck on the side of a road trying to leave a field.

dlstewart01 · November 30, 2010

The G80 locking diff locks the rear wheels together when one wheel spins 100 RPM faster than the other. It will unlock over 20 MPH.

kdixer · November 30, 2010

The G80 locking diff locks the rear wheels together when one wheel spins 100 RPM faster than the other. It will unlock over 20 MPH.

What he said.

Also Traction control limits power at the engine when wheelspin is detected. I have noticed it working even though the warning light is not illuminated on the cluster.

Stabilitrak limits engine power and applies braking in the instance the actual vehicle direction does not match requested vehicle direction.

Both should be turned off if you somehow get stuck.

uchi · December 1, 2010

or sideways if you you so intend it to

It all depends on the situation but yes, they are all passive traction control entities that work together to keep
you going in the path that you are intending to go, forward.

KMGZ400 · December 1, 2010

The G80 locking diff locks the rear wheels together when one wheel spins 100 RPM faster than the other. It will unlock over 20 MPH.

is it 20 or 25mph? i could swear its 25mph... ill have to test as soon as i get out of school

ChevyTech77 · December 1, 2010

or sideways if you you so intend it to
It all depends on the situation but yes, they are all passive traction control entities that work together to keep
you going in the path that you are intending to go, forward.

Aboslutely.

uchi · December 1, 2010

sometimes even by accident, lol.

or sideways if you you so intend it to
It all depends on the situation but yes, they are all passive traction control entities that work together to keep
you going in the path that you are intending to go, forward.

Aboslutely.

dlstewart01 · December 2, 2010

The G80 locking diff locks the rear wheels together when one wheel spins 100 RPM faster than the other. It will unlock over 20 MPH.

is it 20 or 25mph? i could swear its 25mph... ill have to test as soon as i get out of school

How the G80 works...

When the wheel-to-wheel speed difference is 100 RPM or more, the flyweights of the governor will fling out and one of them will contact an edge of the latching bracket. This happens because the left cam side gear and cam plate are rotating at a speed different, either slower or faster, than that of the ring gear and differential case assembly. The cam plate has teeth on its outer diameter surface in mesh with teeth on the shaft of the governor.

As the side gear rotates at a speed different than that of the differential case, the shaft of the governor rotates with enough speed to force the flyweights outward against spring tension. One of the flyweights catches its edge on the closest edge of the latching bracket, which is stationary in the differential case. This latching process triggers a chain of events.

When the governor latches, it stops rotating. A small friction clutch inside the governor allows rotation, with resistance, of the governor shaft while one flyweight is held to the differential case through the latching bracket. The purpose of the governor's latching action is to slow the rotation of the cam plate as compared to the cam side gear. This will cause the cam plate to move out of its detent position.

The cam plate normally is held in its detent position by a small wave spring and detent humps resting in matching notches of the cam side gear. At this point, the ramps of the cam plate ride up on the ramps of the cam side gear, and the cam plate compresses the left clutch pack with a self-energizing action.

As the left clutch pack is compressed, it pushes the cam plate and cam side gear slightly toward the right side of the differential case. This movement of the cam side gear pushes the thrust block which compresses the right-hand side gear clutch pack.

At this point, the force of the self-energizing clutches and the side gear separating force combine to hold the side gears to the differential case in the locking stage.

The entire locking process occurs in less than 1 second. The process works with either the left or right wheel spinning, due to the design of the governor and cam mechanism. A torque reversal of any kind will unlatch the governor, causing the cam plate to ride back down to its detent position. Cornering or deceleration during a transmission shift will cause a torque reversal of this type. The differential unit returns to its open diff function.

The self-energizing process would not occur if it were not for the action of one of the left clutch discs. This energizing disc provides the holding force of the ramping action to occur. It is the only disc which is splined to the cam plate itself. The other splined discs fit on the cam side gear.

If the rotating speed of the ring gear and differential case assembly is high enough, the latching bracket will pivot due to centrifugal force. This will move the flyweights so that no locking is permitted. During vehicle driving, this happens at approximately 32 km/h (20 mph) and continues at faster speeds.

When comparing the effectiveness of the locking differential, in terms of percent-of-grade capability to open and limited-slip units, the locking differential has nearly 3 times the potential of the limited-slip unit under the same conditions.