Originally Posted by Kabigon
Can you elaborate on that? What exactly is the difference?
Other than the noted difference that the later 12B37 programming and the 13 seems to not shift to 6th before 40 mph I don't expect there to be any difference between a 12 that works and a 13 that works, except for the age of the vehicle.
This was something I was trying to gather and figure out also, and other than a few minor ancillary changes that don't directly affect the transmission itself per the other user's description which concurs that BV6Z-7000-F is the latest and greatest transmission assembly and from what I can see was used at least from the timeframe mentioned in the original 12B37 software calibration as being the production applied fix date of 3/28/12 or later.
Noting an axle shaft part number change without documenting what was actually changed as far as the actual part doesn't exactly mean much. Since as far as an engineering change notice something as simple as changing a dimension on the print can call for a new part revision, usually those are minor though like from rev AA to AB, etc. Especially when the main reported problems existed between the clutch plates and the input shaft seals as far as oil contamination was concerned.