I mentioned it briefly in another thread, but I figured I would start a new thread devoted to the new 2015.5+ TCM just to give everyone a heads up the details.

Mid-year 2015, roughly after August 2014 build date, GM/Allison made some changes to the transmission wiring harness, changed to a new TCM, and new speed sensors.

The speed sensors changed from the traditional AC 'analog' variable-reluctance type (IE, the type that has been around for 30 years) to newer DC hall-effect sensors that produce digital (square wave) signals. DC/hall-effect sensors are more accurate, less susceptible to signal noise/interference.

And from an electrical/technical standpoint, its also possible with DC sensors for the TCM's to run more advanced diagnostics on the circuit and sensor...which gives more precise information to the scan tool when there is a fault, thus making it easier for technicians to diagnose problems.

If you have a 2015 truck, look at your glovebox RPO sticker... if you see the code "AVF", that means your truck is a late-build 2015, and has the new DC speed sensors and new TCM.

The TCM on 2015.5+ trucks with "AVF" RPO code is completely different. The 2015.5/AVF trucks no longer use an Allison A40/A50/T14 controller. They now use the GM T87 controller. It looks completely different, has a different connector, and is made by Hitachi. Its the same TCM that the 8-speed 8L90 in the new Corvette and 6.2 half ton Silverados has.

So now the Corvette (w/ 8-speed auto), 2015+ half ton silverado (w/ 8-speed auto), and 2015.5+ Silverado HD (w/ Allison and AVF code) all share the same new T87 controller. Note: the T87 is NOT the same controller that the Aisin 8-speed in the new CTS uses, the T87 is Hitachi and supposedly runs all GM-in-house software.

The T87 is on parts restriction from GM (p/n 24272004)[SIZE=4px][/SIZE], but Im sure at some point Ross will get his hands on one to let 8-speed 'Vette and 2015.5+ Allison guys play around.

Ben