Locking diff question

[sareljr]

This may sound stupid but I have a 05 2500HD and I was curious, how does the rear end "unlock", I've noticed if mine locks and I put it back into park it will unlock but is there another way to unlock it after you get out of the bad road conditions? I don't want to tear up my rear end turning on dry pavement afterwards with a still locked rear end.

[Silverado4x4]

It stays unlocked until its senses a difference in left to right wheel speed of 100 rpm's then it locks. It will also not lock if your stuck in the mud and your spinning the rear wheels faster then 25 mph. That's why you will hear some people say there rear is not locking is because when they get stuck they smash the peddle and get the wheel speed above 25 mph, that's there to prevent rear explosion if it locked at high wheel speed.

 

When stuck you keep the wheel speed low (below 25 mph) until the rear locks. I always just spin the wheels very slow until I hear it lock.

[newdude]

I'm not sure that the noise you are hearing when you put the truck in park is the locker...

 

That said, what Silverado4x4 stated is pretty much on as far as the GM locker goes. Does it all on its own as far as locking at 100rpm difference and unlocking over 25mph.

[sareljr]

So automatically it unlocks at 25mph? I don't hear mine unlock but when I turn I can tell whether it's locked or not.

[kstruckcountry]

Once it is locked, it will only unlock when power to it is cut. Letting off the gas, shifting gears, etc. As far as I can tell if it locks under 20, it can stay locked when the truck exceeds 20 as long as power is constantly going to it.

[ATMINF]

It's a pretty good "clunk" , so some people get off the gas then the locker unlocks, and then people think the lockers not working. Basically keep on the gas, until you get unstuck, keep it below 25mph, smooth and constant. And yes it basically unlocks above 25mph most of the time, due to the way it is designed.

[Silverado4x4]

I forgot to add the clunk you feel when you put it in park after a drive is most likely the slip yoke going in the trans that needs lubed.

[sdeeter19555]

If it stayed locked and you made a turn, you would know it...the inside tire would slide.

 

Sent from my SAMSUNG-SM-G730A using Tapatalk

 

 

[sareljr]

Ya when it's locked and you turn you can just tell it's still locked, mine doesn't make any clunking sound when I put it in park.

[gmtech4]

Locking Function

Locking action occurs through the use of some special
parts:

• A governor mechanism with 2 flyweights
• A latching bracket
• The left side cam plate and cam side gear

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
limited-slip 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.