4WD transfer case in AWD Yukon?

[Avery read]

I have a 2005 gmc yukon Denali AWD. I replaced my transfer case with one that matches my vin. The transfer case I took out the truck that’s been fine for 2 years since I bought the truck was a GM 246 transfer case. Which comes back to a 4WD electric shift transfer case.

The transfer case I put in my truck is indeed for an AWD and doesn’t have the electric shift, but now my truck now won’t move. Why is this? Why does the transfer case that goes to my truck not work, But the one that was in it does work but it’s supposedly the wrong one

 

[Mudsport96]

Maybe the case you just put in is bad.

Does park hold or does it roll?

 

[Avery read]

Maybe the case you just put in is bad.

Does park hold or does it roll?

Grinds when I try to put it in park if the truck is running. Have to shut the truck off. I keep a block behind the wheel so not sure if it rolls. Didn’t want to chance it.

 

[Fless]

Something funny going on here -- a Denali that year is OE AWD and the NP246 two-speed transfer case is not a match for that system.

 

[Avery read]

Something funny going on here -- a Denali that year is OE AWD and the NP246 two-speed transfer case is not a match for that system.

That’s what thought too. But that’s what I’ve been running for the last 2 years. Could they have changed diffs? Or would the differential still be the same no matter what TC?

 

[Fless]

The front diff used with a two-speed Auto T/C has an actuator on it; the AWD diff doesn't since it's always engaged. Does this thing have a dash button to engage the T/C? Pic?

What N** RPO codes are shown in the glovebox, and does the VIN on that sticker match the vehicle VIN?

 

[randeez]

blew up the front diff thinking it was the tcase and replaced with an np246 and has been in 2wd since?

 

[Avery read]

The front diff used with a two-speed Auto T/C has an actuator on it; the AWD diff doesn't since it's always engaged. Does this thing have a dash button to engage the T/C? Pic?

What N** RPO codes are shown in the glovebox, and does the VIN on that sticker match the vehicle VIN?

I would have to check. But no it doesn’t have a dash button. VIN reads AWD 6.0 Denali which it is.

 

[Avery read]

blew up the front diff thinking it was the tcase and replaced with an np246 and has been in 2wd since?

Front diff is fine. Old TC case is out of truck. Can spin it over and hear the grinding inside.

 

[Mudsport96]

If the transmission grinds when you put it in park, that means the internals are spinning and the transfer case is...

A. Internally broken and letting the output shaft of the transmission spin while not putting power to the driveshafts.
B. The output of the transmission is not engaging the input of the AWD case.


Are BOTH driveshafts installed?

 

[Avery read]

I would have to check. But no it doesn’t have a dash button. VIN reads AWD 6.0 Denali which

B

If the transmission grinds when you put it in park, that means the internals are spinning and the transfer case is...

A. Internally broken and letting the output shaft of the transmission spin while not putting power to the driveshafts.
B. The output of the transmission is not engaging the input of the AWD case.


Are BOTH driveshafts installed?

Yes Both drive shafts are installed. I replaced cv axles yesterday thinking maybe that’s why, but it broke my cv axle at the top. So the front dif was spinning but nothing is engaging or giving enough power to move the Yukon. Truck is lifted But cv angles are normal.


Also before I put the TC on the truck. I made sure both inputs moved and spun how they should.

 

[Mudsport96]

Grinds when I try to put it in park if the truck is running. Have to shut the truck off.

This tells me that EITHER the transmission output is slipping in the case. Or the case is damaged internally. It could spin fine by hand no load, then when engine power is applied with vehicle weight it slips. If it grinds going into park, the output shaft of the transmission IS SPINNING. The grind you hear is the parking pall trying to engage a spinning tab. If the transmission output is spinning...then it is not transferring the spinning to the case input. OR the case input is not transferring the spinning to the case outputs.

I had a np233 do that in low. It would drive fine in 2hi and 4hi. But in low under more than 1/3 throttle it would grind and go nowhere.

I keep a block behind the wheel so not sure if it rolls. Didn’t want to chance it.

Put the vehicle in park. And remove the block to see if you can roll it.

ALTERNATIVELY, have some one put it in gear while you CAREFULLY look under the vehicle to see if the driveshafts spin. If they do not.... This will rule out the possibility that somehow BOTH differentials are broken at the same time.

 

[Avery read]

This tells me that EITHER the transmission output is slipping in the case. Or the case is damaged internally. It could spin fine by hand no load, then when engine power is applied with vehicle weight it slips. If it grinds going into park, the output shaft of the transmission IS SPINNING. The grind you hear is the parking pall trying to engage a spinning tab. If the transmission output is spinning...then it is not transferring the spinning to the case input. OR the case input is not transferring the spinning to the case outputs.

I had a np233 do that in low. It would drive fine in 2hi and 4hi. But in low under more than 1/3 throttle it would grind and go nowhere.



Put the vehicle in park. And remove the block to see if you can roll it.

ALTERNATIVELY, have some one put it in gear while you CAREFULLY look under the vehicle to see if the driveshafts spin. If they do not.... This will rule out the possibility that somehow BOTH differentials are broken at the same time.

But since it’s an AWD if my front is off the ground and my front shaft and front wheels spin while the vehicle is in drive, wouldn’t that mean it’s good? Because AWD applies power to the wheels with least traction. And if it didn’t spin then I’d have an issue at the TCASE or the diff ?

 

[Mudsport96]

Ok....


So you have tried driving with all 4 wheels on the ground and it does not move... correct?


Second.

You put it in gear with the front wheels up in the air and rear and rear wheels on the ground and the front tires spin but the rear tires did not push the vehicle? This seems super dangerous to me..
I did not understand this statement?

Third.
Back to the putting it in park makes it grind. We're the front wheels up when you did this or all 4 on the ground?

 

[Mudsport96]

Because AWD applies power to the wheels with least traction. And if it didn’t spin then I’d have an issue at the TCASE or the diff ?

It depends how the case is designed. Some only apply a given amount of power to the front.

 

[BigDogYJ]

if its grinding when put in park, sounds like the Tcase is in neutral. If you have access to a tech2 you can see if the encoder motor on the Tcase can communicate and verify the current shift position.