Cummins12V98 wrote:
I'm thinkin that GM 4500 has a different Allison than the pickups do.
The trans will depend on how the truck is speced to be used. In some applications, like for use as a motor home, it is the Allison 1000 HS while some of the others it is the 2000 HS. Only these two transmissions series will be offered. All Allison 1000/2000 series transmissions are externally identical and use the same case.
This is why I say that GM could easily use a 2000 series in place of the 1000 series if the trans is what is holding them back like you say and they really wanted to get into the towing wars.