Locking Rear Diff

gmyeah · August 11, 2011

I have a 08 sierra z71 4x4. i recently watched a test in which they compared the 4wd systems on 4 manufactures (GM, Ford, Nissan, Toyota) for 1/2 ton pickups. I think I understand the way my 4WD system works, but some of the shows findings made me question how it all works. I understand that my truck has an open diff in the front and rear, and to compensate for losing traction with the rear open differential they have added a locking rear diff which locks the rear up at some point when your spinning at certain rate. One of the comments in the show was that either the nissan or toyota (I forget exactly which one) dissegages locking rear diff when in 4wd (or maybe 2wd too). so you can imagine how the truck struggles a bit when in 4wd on a slippery surface. So I guess 1/2 ton 4WD systems aren't created equally. Does this sound right? and do I understand my system correctly? Thanks in advance!!!

kdixer · August 11, 2011

I have a 08 sierra z71 4x4. i recently watched a test in which they compared the 4wd systems on 4 manufactures (GM, Ford, Nissan, Toyota) for 1/2 ton pickups. I think I understand the way my 4WD system works, but some of the shows findings made me question how it all works. I understand that my truck has an open diff in the front and rear, and to compensate for losing traction with the rear open differential they have added a locking rear diff which locks the rear up at some point when your spinning at certain rate. One of the comments in the show was that either the nissan or toyota (I forget exactly which one) dissegages locking rear diff when in 4wd (or maybe 2wd too). so you can imagine how the truck struggles a bit when in 4wd on a slippery surface. So I guess 1/2 ton 4WD systems aren't created equally. Does this sound right? and do I understand my system correctly? Thanks in advance!!!

If you have the G80 locker, which I would say you do since it is a z71, it locks when there is 100rpm difference between the two rear tires. It disengages @ 20mph. It functions mechanically via centrifugal force and is fully automatic. It does not need any input from the driver.

However there are people that really do not understand how it works and they often complain about it. For instance, if you get stuck and spin the tires faster than 20mph, the locker will disengage and not be of any benefit. Another scenario is where people romp the gas and the locker will engage and kick the rear of the truck out to the side. The best thing to do is spin until you hear or feel it lock and then be steady with the gas.

Most vehicles with an OEM diff locker will only allow the locker to engage in 4wd low. And you have to be stopped to engage it. this is good for rock crawling or mudding. But it is virtually useless on public roadways in inclimate weather. Gm's g80 locker is ideal for daily driving. And while it can be a benefit in offroading, the manual locker is typically best for these instances.

gmyeah · August 12, 2011

I have a 08 sierra z71 4x4. i recently watched a test in which they compared the 4wd systems on 4 manufactures (GM, Ford, Nissan, Toyota) for 1/2 ton pickups. I think I understand the way my 4WD system works, but some of the shows findings made me question how it all works. I understand that my truck has an open diff in the front and rear, and to compensate for losing traction with the rear open differential they have added a locking rear diff which locks the rear up at some point when your spinning at certain rate. One of the comments in the show was that either the nissan or toyota (I forget exactly which one) dissegages locking rear diff when in 4wd (or maybe 2wd too). so you can imagine how the truck struggles a bit when in 4wd on a slippery surface. So I guess 1/2 ton 4WD systems aren't created equally. Does this sound right? and do I understand my system correctly? Thanks in advance!!!

If you have the G80 locker, which I would say you do since it is a z71, it locks when there is 100rpm difference between the two rear tires. It disengages @ 20mph. It functions mechanically via centrifugal force and is fully automatic. It does not need any input from the driver.

However there are people that really do not understand how it works and they often complain about it. For instance, if you get stuck and spin the tires faster than 20mph, the locker will disengage and not be of any benefit. Another scenario is where people romp the gas and the locker will engage and kick the rear of the truck out to the side. The best thing to do is spin until you hear or feel it lock and then be steady with the gas.

Most vehicles with an OEM diff locker will only allow the locker to engage in 4wd low. And you have to be stopped to engage it. this is good for rock crawling or mudding. But it is virtually useless on public roadways in inclimate weather. Gm's g80 locker is ideal for daily driving. And while it can be a benefit in offroading, the manual locker is typically best for these instances.

So, just so I do understand this correctly,...you said most oem diff locker engage ini 4wd low. so, my z71...which does have the g80 (i confirmed it) only engages in 4wd? so in 2wd, the rear wheels will just spin regardless of the rpm?

jro909 · August 12, 2011

no the g80 will lock anytime it feels slippage...my 2wd has a g80 so their for no 4x4 means it will lock if i'm in 2wd

kdixer · August 12, 2011

I have a 08 sierra z71 4x4. i recently watched a test in which they compared the 4wd systems on 4 manufactures (GM, Ford, Nissan, Toyota) for 1/2 ton pickups. I think I understand the way my 4WD system works, but some of the shows findings made me question how it all works. I understand that my truck has an open diff in the front and rear, and to compensate for losing traction with the rear open differential they have added a locking rear diff which locks the rear up at some point when your spinning at certain rate. One of the comments in the show was that either the nissan or toyota (I forget exactly which one) dissegages locking rear diff when in 4wd (or maybe 2wd too). so you can imagine how the truck struggles a bit when in 4wd on a slippery surface. So I guess 1/2 ton 4WD systems aren't created equally. Does this sound right? and do I understand my system correctly? Thanks in advance!!!

If you have the G80 locker, which I would say you do since it is a z71, it locks when there is 100rpm difference between the two rear tires. It disengages @ 20mph. It functions mechanically via centrifugal force and is fully automatic. It does not need any input from the driver.

However there are people that really do not understand how it works and they often complain about it. For instance, if you get stuck and spin the tires faster than 20mph, the locker will disengage and not be of any benefit. Another scenario is where people romp the gas and the locker will engage and kick the rear of the truck out to the side. The best thing to do is spin until you hear or feel it lock and then be steady with the gas.

Most vehicles with an OEM diff locker will only allow the locker to engage in 4wd low. And you have to be stopped to engage it. this is good for rock crawling or mudding. But it is virtually useless on public roadways in inclimate weather. Gm's g80 locker is ideal for daily driving. And while it can be a benefit in offroading, the manual locker is typically best for these instances.

So, just so I do understand this correctly,...you said most oem diff locker engage ini 4wd low. so, my z71...which does have the g80 (i confirmed it) only engages in 4wd? so in 2wd, the rear wheels will just spin regardless of the rpm?

I suppose what I should have said is most vehicles with an OEM manual locker. These lockers typically require you to stop and flip a switch to engage.

As JR909 stated even some 2wd chevys have the G80 and it requires absolutley no driver input. It is always active and is controlled by centrifugal force. There are some really good youtube videos that show how it works. Just keep in mind that is takes wheelspin to engage, and it disengages at around 20mph. So if you get stuck you need spin a little to get it to engage, but do not spin faster than 20mph or it will unlock.