Next month will be three years and nearly 16,000 miles since replacing the head gaskets on my 2001 GMC Duramax 6600.

Here's an update...

There has been no coolant loss or abnormal cooling system pressure. The truck has now experienced three winters since the head gasket project - with winter 22/23 seeing as low as -30 degrees F. Once solving the 10mm coolant hose leak a while back, there have been no engine-related issues. Over the past 3 years, the truck was driven on a few longer trips of a 200-300 miles each, some during the winter and some during the summer.

The truck has set a P0700 code (generic all-encompassing Allison trans code) now and then during this time, and even going back to a year or two before the head gasket work. It comes and goes... The transmission has been serviced twice - replacing the fluid and both filters. The most recent trans service was summer 2021. The root problem with the trans code may be related to a contact issue for one of the pins at the transmission's electrical connector. This has been reported by others on the Internet. The code setting hasn't produced a change in how the engine/trans runs or performs. I'll try to get the problem totally resolved this summer. In the meantime... it's a backburner issue. If anyone can add to this P0700 diagnosis, pls let me know.