Bad trans or transfer case?

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strutaeng

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I'm not familiar with the AWD Tcases, but I'm assuming you can hook up a scanner and monitor speed sensors to see where the problem lies? IDk if the 4L60e in this vehicle has an input speed sensor? I know it has an output speed sensor. The Tcase I'm assuming also has speed sensor(s). This is the Tcase where you can't switch into 2Hi/N/4Hi/4LO, right?

Does the speedometer register anything? I wonder where the speedometer gets its signal?
 

rockola1971

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The tcase can fail, as mine did. It’s the hole that gets work into the tail shaft housing and eventually leaks out all the fluid. Burns up the bearings fast. If you drain yours and there’s lots of fluid in it and it doesn’t look sparkly, then the tcase may be ok or just broke a chain maybe. Grasping at straws here. I narrowed it down by putting the rear on jack stands and the tranny in drive. I think you said you had awd so that may be a bit more difficult. For mine it was really easy to tell where the noises came from.
The pump rub applies to a NP246 Tcase. His AWD is a Borg Warner unit. 2 completely different animals.
 

rockola1971

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Have a 2005 GMC Yukon, 5.3 all wheel drive. Wife was driving it and suddenly it wouldn't go, she gave it more gas and it clunked and started to go but was now making noise. She pulled off the road and got a tow home. Turns out, now it's not holding in park, when shifted to reverse with brakes being held it makes a super loud grinding noise. Shift to drive with brakes applied and and there is no noise until you let off the brakes and the tires start to move. I'm suspecting a bad transfer case but do these symptoms match up? Also, when I went to drain the Tcase, there was way too much fluid in there, so it must also have a bad rear seal. Could this have contributed to failure? Thanks for the help.
"when shifted to reverse with brakes being held it makes a super loud grinding noise." There is your clue. When the brakes are applied, the Tcase, Driveshaft and rear end are not rotating. But internally the transmission is. Its your transmission, not your Tcase. And the damage is likely in the rear half of your tranny.
 
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Peeledpeas

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Working on getting the tcase out. Have everything unbolted just have to figure out a way to lower it to the floor without breaking it or hurting myself. I don't have a trans jack.
 

nonickatall

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Have a 2005 GMC Yukon, 5.3 all wheel drive. Wife was driving it and suddenly it wouldn't go, she gave it more gas and it clunked and started to go but was now making noise. She pulled off the road and got a tow home. Turns out, now it's not holding in park, when shifted to reverse with brakes being held it makes a super loud grinding noise. Shift to drive with brakes applied and and there is no noise until you let off the brakes and the tires start to move. I'm suspecting a bad transfer case but do these symptoms match up? Also, when I went to drain the Tcase, there was way too much fluid in there, so it must also have a bad rear seal. Could this have contributed to failure? Thanks for the help.
Do you still have propulsion when you switch to D?

Pobably not, otherwise your wife wouldn't have the need to be towed.
Foe me it sounds like the clutch pack for the reverse gear has broken down and caused damage to the transmission.

But of course it can't be ruled out that something has broken down in the transfer gearbox, which only makes noise when turning backwards might.

Does the GMC have permanent all-wheel drive or switchable four-wheel drive?

The first thing I would do, is lay under the car and carefully open the oil drain plug from the transfer gearbox and drain some oil and see if there are any chips there. When was the automatic transmission fluid last changed?

Take the dipstick out and smell it to see if it smells burnt.
 
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Peeledpeas

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Do you still have propulsion when you switch to D?

Pobably not, otherwise your wife wouldn't have the need to be towed.
Foe me it sounds like the clutch pack for the reverse gear has broken down and caused damage to the transmission.

But of course it can't be ruled out that something has broken down in the transfer gearbox, which only makes noise when turning backwards might.

Does the GMC have permanent all-wheel drive or switchable four-wheel drive?

The first thing I would do, is lay under the car and carefully open the oil drain plug from the transfer gearbox and drain some oil and see if there are any chips there. When was the automatic transmission fluid last changed?

Take the dipstick out and smell it to see if it smells burnt.
I got motivated and dropped the T case an split it open. Nothing wrong in there so I went ahead and dropped the trans pan and found metal bits. I guess I have my answer. Now we're trying to figure out how far we want to go with it.
 

rockola1971

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I got motivated and dropped the T case an split it open. Nothing wrong in there so I went ahead and dropped the trans pan and found metal bits. I guess I have my answer. Now we're trying to figure out how far we want to go with it.
Your problems will be in the back half of the tranny and it will be fragged. You will need some new hard parts as well as a complete rebuild kit whether you or someone else does the deed. I called this one in post#14. Unfortunately I was right and this is gonna get expensive. Good Luck to you man.
 

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