Bad trans or transfer case?

[Peeledpeas]

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.

 

[Sam Harris]

Damn. Sorry to hear this. I think I’d try to get it off the ground, and start moving wheels independently, and listening for noise with a mechanic stethoscope. If you can’t determine anything from that, might try the same while running, in gear, etc.. would be ideal while on a lift, but as long as you’re careful, can pretty easily be done on jackstands as well.

 

[strutaeng]

It's possible the transmission leaked into the T-case and transmission is now low on fluid? Have you checked the transmission fluid yet?

 

[Joseph Garcia]

@NickTransmissions

 

[V327839]

As I just swapped a tcase on my 04 Sub, the tcase and trans do not share fluid in any way. There is a breather type hole in the back of the trans where fluid can seep into the adapter. I found that out when I pulled my trans and fluid ran right out that hole. Don’t even know why it’s there. Anyway, the adapter is sealed both ends. If one of the gaskets leaked then you could have leaked tranny fluid. The tcase uses its own fluid, although I’m not sure what the awd tcases used, but they are self contained. A failed tcase, like mine, will manifest noise only while in motion. This is just my understanding from my experience.

 

[Peeledpeas]

I know the rear seal leaked into the Tcase. The reason I'm suspecting Tcase is because it doesn't hold it in park. I'm trying to figure out if the Tcase can fail and cause my symptoms because it feels like the park pawl is actually working and it also feels like it's going into gear. No noise in drive while holding brakes, super noisy in reverse while holding brakes. So, I'm thinking maybe something let go in the tacse that would do that.

 

[Peeledpeas]

Now that I think about, I forgot that we had a weird clunk that was like a bad ujoint a few weeks ago. But I wrote it off as imagining things when I didn't find any bad ujoints. I was hoping to find someone here that may have dug into one of these before.

 

[Jimmyy]

If it is a AWD the front and rear work like a open differential. If your rear wheels are on ice and the front on dry ground its possible for the truck to roll until a rear wheel catches a dry spot. You need to get all 4 wheels in the air and check it out.

 

[Jimmyy]

You could lift the back (block the front) and disconnect the drive shaft and spin the rear end to eliminate the rear-end.

 

[V327839]

I know the rear seal leaked into the Tcase. The reason I'm suspecting Tcase is because it doesn't hold it in park. I'm trying to figure out if the Tcase can fail and cause my symptoms because it feels like the park pawl is actually working and it also feels like it's going into gear. No noise in drive while holding brakes, super noisy in reverse while holding brakes. So, I'm thinking maybe something let go in the tacse that would do that.

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.

 

[strutaeng]

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?

 

[Peeledpeas]

This is the Borg Warner all wheel drive t-case. There is no 2Hi.

 

[rockola1971]

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]

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.

 

[Peeledpeas]

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]

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.

 

[Peeledpeas]

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]

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.

 

[Peeledpeas]

I found a used transmission with a 6 month warranty. I have no clue how to rebuild a transmission myself so I'll put this used one in and hope for the best.

 

[Peeledpeas]

BTW, here's a pic of the carnage.