2007 Chevrolet Avalanche Transmission Failure
 

Son has a 2007 Chevrolet Avalanche 4x4 with 187K miles. Transmission rebuilt over 18 months ago (rebuild warranty has expired).

A few evening ago there was a sudden vibration and the vehicle lost all forward motion. Putting the vehicle in park does not hold the vehicle - there is a clunking sound. Reverse and neutral are fine, but when it is put in Drive it makes a horrible racket and the vehicle will not move forward. He's checked the Universal joints - all appear to be fine.

Any ideas as to what may have failed? He's planning on getting it repaired if the cost isn't too high and then selling or trading it.

Note - I am 400 miles from him and only heard the sound over the phone.

I hate to tell you this but it's going to need to be opened up to determine what failed. If park won't hold, something is broken as the parking pawl engages a notched wheel that attached to the shaft. Did it get inadvertently shifted into park while moving? Does 1 or 2 do anything?

Here's a list of 30 common problems with the 4L60e. 30 Common 4L60e Problems

Maybe the splines on the shaft were damaged inside the trans.

I wouldn't mess with it any. It'll need to be opened up and examined.

He didn't move into 1 or 2. As soon as he put it in D it made a horrible ratcheting sound - loud enough I could hear it via his cell phone which was on speaker. I suspect something with the parking pawl went bad. As far as I know he did not put it in Park while moving but I suppose that is possible.

He has it scheduled to go to a transmission shop (same one that rebuilt it) next Monday - that's the earliest they can look at it. It may be a few days before they have a diagnosis.

I do know when the transmission failed the first time, 1st and 2nd gear worked fine and it was hesitant to go into 3rd and would not go to 4th. Supposedly the entire transmission was rebuilt.

Pending the diagnosis, his plans are to repair it and then sell it. He's had enough of it and is tired of only getting 13 mpg no matter what he does.

Transmission is okay. Differential shot. Apparently the carrier bearings came apart with bearing pieces in the pumpkin. Quoted $2300 for used differential installed. Son is done with it and getting what he can on a trade.

Ouch. I didn't realize the sound was coming from the differential and not the trans. Figured if reverse was working, it was trans. You generally only hear of them breaking catastrophically like that when drag racing at the track. Was it low on fluid maybe?

Me neither. Son wasn't sure where the noise was actually coming from. I'm not sure if the diff was low on fluid. I don't think so, but I can't say for certain. Son lives 400 miles away. As far as reverse working and Drive not working, the tech said when in reverse the axle was pressing in allowing it to work, but in Drive the axle was trying to push out and would lose contact (if that makes any sense). Shop basically said the bearing (carrier, I think) wore out or just plain failed. Vehicle does have 189K miles on it. They did open up the transmission and found nothing wrong. When the opened up the differential they found pieces of the bearings all over.

At any rate, he's done with it and is going to get what he can on a trade.

Son got $4500 for it. Traded for a 2016 Subaru WRX AWD Limited w/6 speed manual.