Transmission Leak on Extreme Cold Starts

[Brad Vogt]

Hey all, first post here. I have a 2013 Sierra 1500 Z71 with the 5.3L and 6L80. The truck currently has 340 000km on it (210k miles), it was my dads truck that he bought new and I bought it from him 2 years ago when he upgraded to the 3L Duramax. Prior to me owning it, the truck was always parked in a heated shop during the winter months, as we live in Canada and it can get as cold as -50 degrees Celsius in January (-50F). So, the first winter that I owned it, it was parked outside; me being newly wed with a single car garage only. Of course, the transmission cooler lines started seeping due to the shock of the extreme cold starts they had not seen before. The truck went to the local GM dealer where it gone since the day it was bought and the lines were replaced. All fixed. Now, fast forward two winters later, and I see another pink spot in the snow under the truck. I’ve checked all the connection points on the lines, both on the radiator and transmission side, and I don’t see any signs of sweating or leaking. I did however, see some drips accumulating on the front sway bar, and it looks as though the leak is coming from the top of the bell housing, or from that thin plate looking piece. Could this be purely because of the cold and the expansion rates of seals and metal being so different? Or is there some sort of vent that the transmission will

puke fluid from if it is too thick to move? Keeping in mind this is the first it’s done it since the lines were replaced, and it’s the coldest week yet hitting the -50C mark overnight. Any thoughts or help would be appreciated!

[CamGTP]

Yes, there is a transmission vent on top of the transmission. I believe it's on the passenger side and then there is a hose with a plastic breather fitting on it that is stuck somewhere up on top of the bell housing. That sort of leak would be on the outside of the transmission.

 

If the leak was forming on that thin metal inspection plate and no where else then it would be from inside the bell housing and pushing past the torque converter seal or front pump seal.

 

I know a lot of people will install a pan heater on the transmission when parked outside because most engines have a block heater.

[Brad Vogt]

Makes sense. Would that be just your standard magnet pan heater that can be placed underneath the transmission?

[CamGTP]

The magnet heaters can get knocked off or you have to crawl under there and remove it all the time. They sell a stick on heater pad that has 3M adhesive backing on it and then you put a bead of silicon around the edges.

 

I use one on my oil pan in the winter months here, it's held up great.

[Brad Vogt]

Awesome, thanks!