Differential OR Transfer Case Shift motor

[jonathonsweed]

Recently I've noticed when my tire spins on ice or a wet surface from a stop, something in the rear end gets clunky, like something is trying to engage but is not. It rides a little rough and bumpy as if the tires are dragging or gears are bumping each other rather than engaging but after driving for a second or two it goes away and rides normally. Also, when I'm making a slow right turn, say into a parking lot, I feel something in the right front dragging or binding, per say, as if the 4x4 is engaged in that tire. I removed the rear differential cover and did not notice any broken teeth or metal in the fluid and the fluid has less than 15K miles on it. I drained the fluid from the transfer case and it was not burnt but I did find some shavings in that fluid. On occasion when I start the vehicle, it will go through the diagnostics and then the 2HI light will blink. If I don't shift to neutral and then back to park it will go out and the 4x4 will not shift. My mechanic seems to think it's the transfer case shift motor. I did purchase one but since I don't know much about this rear end, I'm still wondering if it is in the differential or axle or if it could be the shift motor and that the blinking light is an indicator of the motor. Figured I'd ask here before deciding to change this motor or take it in for further diagnostics. I have researched it but have not found any articles or threads of others that have experienced this issue.
Regards......

https://www.trailvoy.com/threads/di...ther-2003-envoy-xl.218597/reply?quote=1675103

 

[TollKeeper]

Dont need 2 different threads about it...

That said, it sounds like your G80 in your rear axle is getting stuck.

Whens the last time you did a rear diff service? Have you ever done a rear diff service?

 

[Mooseman]

Sure sounds like the transfer case encoder motor and it's stuck in 4hi. If you put the switch to 2hi and the light flashes, if it fails, you should get a service 4x4 light. Since you already bought a motor, I'd just go ahead and replace it. If it does the same thing, there might be something wrong internally given the metal shavings you saw in the fluid. I sure hope not

(Duplicate thread deleted)

 

[Mooseman]

Recently I've noticed when my tire spins on ice or a wet surface from a stop, something in the rear end gets clunky, like something is trying to engage but is not. It rides a little rough and bumpy as if the tires are dragging or gears are bumping each other rather than engaging but after driving for a second or two it goes away and rides normally.

This might be normal. The G80, when one wheels slips, will engage the other wheel, effectively locking it, and will eventually unlock once you get up to speed or make a turn.

The other symptoms with the front wheels are indicative of a transfer case in 4hi.

 

[jonathonsweed]

Dont need 2 different threads about it...

That said, it sounds like your G80 in your rear axle is getting stuck.

Whens the last time you did a rear diff service? Have you ever done a rear diff service?

New here so wasn't sure about posting twice. I did the rear about 15k miles ago and again when we pulled the cover to inspect so it's been services regularly. Not sure what the G80 is but will research it for diagnosis and repair. If you have anything to direct me to that'll help out would be appreciated.

 

[jonathonsweed]

This might be normal. The G80, when one wheels slips, will engage the other wheel, effectively locking it, and will eventually unlock once you get up to speed or make a turn.

The other symptoms with the front wheels are indicative of a transfer case in 4hi.

The thing with the rear is that it doesn't seem to fully engage but sounds like it's trying to. As for the front, I'll change the motor on the transfer case and see if that helps

 

[jonathonsweed]

Sure sounds like the transfer case encoder motor and it's stuck in 4hi. If you put the switch to 2hi and the light flashes, if it fails, you should get a service 4x4 light. Since you already bought a motor, I'd just go ahead and replace it. If it does the same thing, there might be something wrong internally given the metal shavings you saw in the fluid. I sure hope not

(Duplicate thread deleted)

I haven't gotten any service lights for the 4x4. The motor does seem to work but didn't a couple other times. So, yes, will change the motor and hope for the best

 

[mrrsm]

Welcome to GMT Nation...

Cross-Check the Data in your Profile versus the WIKI Linked Below for the correct Engine Displacement.. and notice that the Rear Differential came in two possible flavors: The GM Eaton M-Locker G80...and a Posi-Trac Version as well. Check your Glove Box RPO Sticker-Label for the Alpha-Numeric Codes to figure out which has been installed in your Envoy:

GMC Envoy - Wikipedia

en.wikipedia.org

GM RPO Codes - Axle Ratio and Differential Identification

The GM RPO codes label in your glovebox or on drivers door identifies axle ratios and more. Decipher the codes and get the right parts!

differentials.com

 

[jonathonsweed]

Welcome to GMT Nation...

Cross-Check the Data in your Profile versus the WIKI Linked Below for the correct Engine Displacement.. and notice that the Rear Differential came in two possible flavors: The GM Eaton M-Locker G80...and a Posi-Trac Version as well. Check your Glove Box RPO Sticker-Label for the Alpha-Numeric Codes to figure out which has been installed in your Envoy:

GMC Envoy - Wikipedia

en.wikipedia.org

GM RPO Codes - Axle Ratio and Differential Identification

The GM RPO codes label in your glovebox or on drivers door identifies axle ratios and more. Decipher the codes and get the right parts!

differentials.com

I'm almost positive it is not a posi rear end but will certainly get the codes. I know I can get the last 8 of the Vin to the dealer and they'll tell me also

 

[TollKeeper]

If you want to post your VIN, or PM me your VIN, I can get the build sheet too.

 

[jonathonsweed]

If you want to post your VIN, or PM me your VIN, I can get the build sheet too.

So, I called the dealer and I do have a G80 with a ratio of 3-7-3. Doesn't mean much to me at this time but will research. I found a picture the year down components.

 

[jonathonsweed]

So, I called the dealer and I do have a G80 with a ratio of 3-7-3. Doesn't mean much to me at this time but will research. I found a picture the year down components.

So, I called the dealer and I do have a G80 with a ratio of 3-7-3. Doesn't mean much to me at this time but will research. I found a picture with the tear down components

If you want to post your VIN, or PM me your VIN, I can get the build sheet too.

I can't figure out how to DM you.

 

[TollKeeper]

So... a G80 is a locking rear axle. Simple explanation is you get onto a slippery surface, and spin a wheel. The G80 will kick in, and lock the rear axle so that both wheels spin at the same rotation, at the same time. Its a handy thing to have.

But the G80 does have a weak spot. Some people like to mash the gas when they are stuck, and it can blow out the mechanical engagement pin when to much force is applied.

The G80 also unlocks, by itself, when it no longer is needed, and you are going about 20 mph.

So the big question is, are you experiencing crow hop, or rear axle bind.

Rear axle bind is normal when the rear axle is locked. This happens on the rear axle

Crow hop is normal when the 4x4 system is engaged. This typically happens on the front end.

 

[flyboy2610]

When the front axle disconnect on my '04 TB went out I had the exact symptom you described: A binding/growling noise from the right front.

What did you do to your GMT today? [Part II]

Yesterday was time to give some love to the TB. Replaced the rear brakes with the rotors and pads I had kept from the Saab as they were basically new ACDelco when I scrapped it. The truck would pull to the left when the brakes were applied and the right rear rotor showed uneven rust on the...

gmtnation.com

If you decide you need to replace yours please read the removal instructions in the above post. The disconnect is easy to break if you don't do it right.

 

[jonathonsweed]

So... a G80 is a locking rear axle. Simple explanation is you get onto a slippery surface, and spin a wheel. The G80 will kick in, and lock the rear axle so that both wheels spin at the same rotation, at the same time. Its a handy thing to have.

But the G80 does have a weak spot. Some people like to mash the gas when they are stuck, and it can blow out the mechanical engagement pin when to much force is applied.

The G80 also unlocks, by itself, when it no longer is needed, and you are going about 20 mph.

So the big question is, are you experiencing crow hop, or rear axle bind.

Rear axle bind is normal when the rear axle is locked. This happens on the rear axle

Crow hop is normal when the 4x4 system is engaged. This typically happens on the front end.

The best I can explain it is when the tire spins on ice it feels like gears are bouncing off each other instead of connecting. It kinda hops and makes a cluncking sound. It's smooths out once o go a little bit. It's never done it before when I had tire slip. It was always smooth. It actually did it one morning after it sat over night without the tire slipping. Just started off that way. Also, now that I think of it, a couple times I heard a metallic tinging noise when I was backing a trailer over a curb. There's something not right back there.

 

[TollKeeper]

Check your fluid in the transfer case, make sure its a nice BLUE, and check the fluid in the front and rear diff. It could be a disconnect, or it could be the encoder motor. Fluids are cheap, checking them is free.

 

[azswiss]

Fluids are cheap, checking them is free.

No truer words . . .

 

[TJBaker57]

Here is a video for the locking differential

 

[jonathonsweed]

Check your fluid in the transfer case, make sure its a nice BLUE, and check the fluid in the front and rear diff. It could be a disconnect, or it could be the encoder motor. Fluids are cheap, checking them is free.

I maintain my vehicle very well. The fluid in both the transfer case and differential were recently replaced. Both fluids were in good shape.

 

[jonathonsweed]

Here is a video for the locking differential

Thanks, I watched this and it really helped me to understand the mechanics and how it works. I really appreciate this.

 

[budwich]

I maintain my vehicle very well. The fluid in both the transfer case and differential were recently replaced. Both fluids were in good shape.

Maybe the wrong fluid was used?

 

[mrrsm]

Yup...it CAN Happen...

Use the Gear Oil Mentioned in Post #28 (Amsoil Severe Gear) as it contains NO Limited Slip Additives... The GM Eaton G80 M-Locker Rear Differential Does NOT Require these Additives.

https://gmtnation.com/forums/

http://threads/2000-2002-silverado-rear-diff-partial-rebuild.20455/

 

[Mooseman]

We also have this thread from the FAQ that has methods of diagnosing the 4x4 system:

4WD not working? Step inside.
As for the G80 rear diff, this video show exactly how it works:

and this one how to check it: