Transmission leak!

19gmcsierraat4 · February 11, 2020

Bought a brand new 2019 GMC AT4 with the 6.2 the truck has 5500 miles and it has a transmission leak. Took into the dealership and they replaced a seal. I get it back and put about 100 miles on it. Look under and its leaking again. Take it back to the dealership and they start troubleshooting. They call me 2 days later and say they have to replace the entire transmission. I'm kinda disappointed. New truck not been abused and already having to replace the transmission. Anyone else having issues with their 10 speed transmissions?

davester · February 11, 2020

You're unhappy about this?

The transmission leaking doesn't seem to be a commonly reported issue, This sounds like perhaps they think something is worn (or perhaps GM does) in an unusual way, and are giving you a whole new one, GM may want the transmission back to tear it down and figure out why it failed that way, or perhaps they found something wrong that would take a long time to fix (say, very poor parts availability).

Personally, other than if I would have to wait an extended period of time for the transmission, this is way better than having the local mechanic muck around with the internals of the transmission replacing just the odd part or two, as the transmission will be built by someone who does it all the time, not by someone just learning how the thing goes together.

And you didn't have to go through this a bunch of times. I would have expected the dealer to try slapping parts on it a couple more times before doing a full replacement (depending on what they think is wrong).

Edited February 11, 2020 by davester

spizike9 · February 11, 2020

Not a big deal. Very very few problems have been reported with the 10 speed. While definitely disappointing just be grateful they are taking care of it.

UGADawgs · February 11, 2020

Had the same problem in our Odyssey. Even though it took replacing the right axle seal and the seal between the engine and the tranny, they ended up replacing it due to fluid seaping through the aluminum casting, but that was after multiple trips over a couple years. I'd be happy they addressed yours so quickly.

Jonathan Bowman · May 31, 2020

On 2/10/2020 at 10:53 PM, 19gmcsierraat4 said:

Bought a brand new 2019 GMC AT4 with the 6.2 the truck has 5500 miles and it has a transmission leak. Took into the dealership and they replaced a seal. I get it back and put about 100 miles on it. Look under and its leaking again. Take it back to the dealership and they start troubleshooting. They call me 2 days later and say they have to replace the entire transmission. I'm kinda disappointed. New truck not been abused and already having to replace the transmission. Anyone else having issues with their 10 speed transmissions?

Only 300 miles on mine, having the same issue.

DFW-AT4 · June 1, 2020

7 hours ago, Jonathan Bowman said:

Only 300 miles on mine, having the same issue.

Less than 900 miles on mine, and it was gushing trans fluid when I pulled in the driveway tonight. NOT happy.

Jonathan Bowman · June 1, 2020

Seems this issue is more ubiquitous than I thought. What part of DFW are you from?

DFW-AT4 · June 1, 2020

8 hours ago, Jonathan Bowman said:

Seems this issue is more ubiquitous than I thought. What part of DFW are you from?

Azle & bought my AT4 in Weatherford

kpanza · June 1, 2020

Consider yourself lucky! At 270 miles, mine went in for leak, and they replaced the torque converter seal...few days later, it was brought back because it was still leaking! And now, my truck has been at the dealership for 63 DAYS AND COUNTING! They say they are waiting for a transmission pump. Service manager has requested a new transmission, but nothing from GM. GM has approved a buyback or replacement due to CA Lemon Law, but finding a similar truck (and getting a far away dealer to actually dealer-trade it to my dealer) has been impossible.

Jonathan Bowman · June 1, 2020

38 minutes ago, kpanza said:

Consider yourself lucky! At 270 miles, mine went in for leak, and they replaced the torque converter seal...few days later, it was brought back because it was still leaking! And now, my truck has been at the dealership for 63 DAYS AND COUNTING! They say they are waiting for a transmission pump. Service manager has requested a new transmission, but nothing from GM. GM has approved a buyback or replacement due to CA Lemon Law, but finding a similar truck (and getting a far away dealer to actually dealer-trade it to my dealer) has been impossible.

I feel for you man, luckily I’m also in CA, and I have a feeling I’m headed down the same road as you wrt the transmission.

Jonathan Bowman · June 1, 2020

1 hour ago, kpanza said:

Consider yourself lucky! At 270 miles, mine went in for leak, and they replaced the torque converter seal...few days later, it was brought back because it was still leaking! And now, my truck has been at the dealership for 63 DAYS AND COUNTING! They say they are waiting for a transmission pump. Service manager has requested a new transmission, but nothing from GM. GM has approved a buyback or replacement due to CA Lemon Law, but finding a similar truck (and getting a far away dealer to actually dealer-trade it to my dealer) has been impossible.

Looks like it’s output shaft seal, we shall see if that corrects the problem.

kpanza · June 1, 2020

Wow, that's much further back than mine...at least that's an easier fix. Good luck.

Jonathan Bowman · June 1, 2020

3 hours ago, kpanza said:

Wow, that's much further back than mine...at least that's an easier fix. Good luck.

Mechanic said it looked like someone took a screwdriver to it. Who? No idea. All fixed and ready to.

kpanza · June 1, 2020

Weird! Replaced a few of those in the 208 and 241 t cases in my K5s! Easy fix, glad they took care of you.

Beta 390 · December 25, 2023

I have a 2023 GMC Sierra AT4 with 3.0 Duramax and my truck has been in the shop since 12/5/23. The truck has 10,000 miles and is leaking transmission fluid. I stopped driving it as soon as I noticed the leak and towed the truck to the dealership. They replaced some washers at the thermal block and it still leaked, they replaced the thermal block and it still leaked and now they are replacing the cooler lines. Not real impressed. I never had any issues with my Ram Hemi.... Looks like I will be getting a Ram 2500 Rebel.