Question about how transfer case/diff works

[missouritig]

Ive reviewed a ton of threads and think Ive got this figured out, but would anyone look at this and see if Im incorrect in my understanding of the mechanics here.

Veh is a 2000 3500 4x4 automatic w/ 5.7 gas 4l80e and full float rear axle w/ g80. Manual 4X4 shift lever

Got it stuck in mud and noticed one rear tire spins in 2wd. I vary the throttle speed, other tire never kicks in. I suspect the G80 locking mechanism has failed in the rear diff. I will inspect that at some point.

I place the truck into 4-high and noticed only one front tire spins when stuck and lost traction. My understanding is this is normal and by design in a IFS truck. There is no way to lock the front diff in stock form.

So with a bad g80 im basically a 1wd truck and with 4x4 engaged Im 2wd. Under perfect operation, best I can get is 3x4 if the g80 locks the rear diff.

I was curious to find a manual rear diff locking option but havent found any, best practice appears to be repair the G80.

 

[0xDEADBEEF]

That's correct.

In order to get all 4 wheels turning at the same time/speed you need locking differentials in the axles.

Some transfer cases have a full time mode which allows some slip between the front and rear. In order to get all 4 wheels turning at the same speed you have to also lock the transfer case also known as part time mode. In the Toyota world they call it triple locked.

 

[evilunclegrimace]

The BEST practice is to replace the G80 with a name brand after market unit.

 

[BeXtreme]

There are plenty of options to replace the G80 carrier in a 14BFF. Mine was an open diff, so I added a Grizzly locker. The better option would be to get a Yukon duragrip. It replaces the whole carrier and is much stronger than the stop 14B G80 rear. You cannot do a Grizzly locker in a G80 carrier.

xc_hide_links_from_guests_guests_error_hide_media

The stock G80 will only lock below 25mph. If you are giving it the beans in some mud it could potentially be unlocking if the wheels are spinning about 20mph or so.

 

[Dariusz Salomon]

Ive reviewed a ton of threads and think Ive got this figured out, but would anyone look at this and see if Im incorrect in my understanding of the mechanics here.

Veh is a 2000 3500 4x4 automatic w/ 5.7 gas 4l80e and full float rear axle w/ g80. Manual 4X4 shift lever

Got it stuck in mud and noticed one rear tire spins in 2wd. I vary the throttle speed, other tire never kicks in. I suspect the G80 locking mechanism has failed in the rear diff. I will inspect that at some point.

I place the truck into 4-high and noticed only one front tire spins when stuck and lost traction. My understanding is this is normal and by design in a IFS truck. There is no way to lock the front diff in stock form.

So with a bad g80 im basically a 1wd truck and with 4x4 engaged Im 2wd. Under perfect operation, best I can get is 3x4 if the g80 locks the rear diff.

I was curious to find a manual rear diff locking option but havent found any, best practice appears to be repair the G80.

My g80 doesn't work and I gave up on it as it's a bit of a time bomb. With current 4x4 it's capable to climb up the snowy hill-but if you want to do some serious off roading guys like Don Yukon and others can shed more light on the subject.

 

[Schurkey]

I was curious to find a manual rear diff locking option but havent found any, best practice appears to be repair the G80.

Should be possible to repair the G80. Question is whether you think it's worth the trouble.

The BEST practice is to replace the G80 with a name brand after market unit.

There are plenty of options to replace the G80 carrier in a 14BFF.

My open 10.5" full-float differential got replaced with a Truetrac diff.
For your purposes, you could ignore the first three posts.

10.5" Full Float Truetrac Differential Installation

1997 K2500 8-lug 10.5” Ring Gear Full-Float axle Truetrac Differential Installation Driveline Tragedy and Heartache, Ending in Success. Intended to install an Eaton Truetrac helical-gear style “posi” in the 8-lug '97 K2500 plow truck, 10.5” full-float rear axle last summer. Things got put...

www.gmt400.com

The stock G80 will only lock below 25mph. If you are giving it the beans in some mud it could potentially be unlocking if the wheels are spinning about 20mph or so.

Yup. But if the differential locks, and is kept under torque, it should remain locked even above 25mph. Once the torque is removed, it'll unlock.

My g80 doesn't work and I gave up on it as it's a bit of a time bomb.

The 8.5" and smaller Gov-Bombs have a very poor reputation. The 9.5" and larger aren't so bad,

 

[df2x4]

I'm in the "replace the G80 with a better locker" camp, but...

Those of you with G80s that aren't functioning properly, are you 100% sure that you're running the correct GL5 80W/90 gear oil with NO friction modifiers or LSD additives? GM released a service bulletin about this but it seems like many people aren't aware. Using a friction modifier or additive can cause erratic behavior with the G80s. I've experienced it first hand in my red truck with the 10 bolt. Draining the oil with additive and replacing it with this ACDelco 10-4051 fixed the issue for me.

www.amazon.com/gp/product/B007Q10F3S

 

[Dariusz Salomon]

Should be possible to repair the G80. Question is whether you think it's worth the trouble.




My open 10.5" full-float differential got replaced with a Truetrac diff.
For your purposes, you could ignore the first three posts.

10.5" Full Float Truetrac Differential Installation

1997 K2500 8-lug 10.5” Ring Gear Full-Float axle Truetrac Differential Installation Driveline Tragedy and Heartache, Ending in Success. Intended to install an Eaton Truetrac helical-gear style “posi” in the 8-lug '97 K2500 plow truck, 10.5” full-float rear axle last summer. Things got put...

www.gmt400.com

Yup. But if the differential locks, and is kept under torque, it should remain locked even above 25mph. Once the torque is removed, it'll unlock.


The 8.5" and smaller Gov-Bombs have a very poor reputation. The 9.5" and larger aren't so bad,

Mine's 8.5 so...yeah.

 

[Dariusz Salomon]

I'm in the "replace the G80 with a better locker" camp, but...

Those of you with G80s that aren't functioning properly, are you 100% sure that you're running the correct GL5 80W/90 gear oil with NO friction modifiers or LSD additives? GM released a service bulletin about this but it seems like many people aren't aware. Using a friction modifier or additive can cause erratic behavior with the G80s. I've experienced it first hand in my red truck with the 10 bolt. Draining the oil with additive and replacing it with this ACDelco 10-4051 fixed the issue for me.

www.amazon.com/gp/product/B007Q10F3S

In those the governor axles shed a tooth and it's most likely what happened to his (it happened to mine-I found that tooth on the magnet)-tho I'm not saying you're wrong. It just struck me that the diff survived rather than G80 so that's a good news lol.
My friend has a Colorado with g80-and his kicked in as he was going round the bend in the rain and one wheel lost the traction-it sent him to the road's lanes concrete divider and crashed his truck-nothing happened to him and he repaired it,but he never saw this one coming.

 

[Pinger]

So with a bad g80 im basically a 1wd truck and with 4x4 engaged Im 2wd.

Nope - that's zero WD. Open diffs distribute torque equally. If there's no torque at one wheel because it's spinning, there's no torque at the other even though it has grip.
The only way to get torque to the wheel with grip is to allow both wheels to stop turning then use the throttle. The inertia of the wheel that will spin permits torque on its half shaft which will be replicated at the wheel with grip. This only works for as long as the wheel is accelerating. When it reaches its maximum speed, the effect is lost.

Under perfect operation, best I can get is 3x4 if the g80 locks the rear diff.

See above. If a front wheel is spinning there will be zero torque at the front axle. A functioning G80 will drive both rear wheels though (within the grip and speed limitations). So, either 4WD (if there's traction at the front) or 2WD (if there isn't).