Alison transmission

[GOTTOYS]

I worked in the service dept of a couple GM dealers. We replaced hundreds of those transmission cooler lines on gassers and diesels because they leaked at the crimped fittings. GM didn't seem to care they just kept making them the same way for years...I drive a Dodge...Don

 

[Westwind]

I have 57K on my 2008 GMC Sierra D/A and I'm replacing my first transmission cooler line with a set made up from Hydraulic lines fabricated by Alligator Performance, from what I've read online they should solve a repeat problem. Other than this I've had no problems and love the way it functions and works. It was one of the reasons I bought this truck and of course the Duramax.

 

[porthole]

This must be a geographical issue, due to cold temperatures.

I'm sure it is Scotty. Although I used the remote start year round, I only found seeps-leaks after the winter season. Fuel waster or not, there wasn't a sub 30 degree day where I didn't use the remote.

See Don's post above and where he lives - will give a hint to th e"geographic nature" of this problem.
The factory lines are a pain in the butt to replace. Enough so that after changing all three the first time I only changed the leakers after that.
There are several aftermarket kits available and all of them are way easier to install.