You only mention the Allison 6-speed (and 10 speed) transmission in connection with the Duramax engine.
I have a 2008 Thomas 4-window short bus built on a 2007 Chevrolet Express 3500 chassis, GVWR 12,300#.
It came with an LMM Duramax 6.6L and a GM 4L85-E four speed transmission and a 3.73:1 axle.
So at least occasionally they used a 4L85-E.
I was lucky to find one so new, the maintenance guy at First Student said they were expecting to keep it a couple more years, so I got it with only 140K-odd miles and fully up-to-snuff, but corporate sent them a batch of new busses, so this one became my Bus Named Sue.
Now to get on with finishing it.
I have a 2008 Thomas 4-window short bus built on a 2007 Chevrolet Express 3500 chassis, GVWR 12,300#.
It came with an LMM Duramax 6.6L and a GM 4L85-E four speed transmission and a 3.73:1 axle.
So at least occasionally they used a 4L85-E.
I was lucky to find one so new, the maintenance guy at First Student said they were expecting to keep it a couple more years, so I got it with only 140K-odd miles and fully up-to-snuff, but corporate sent them a batch of new busses, so this one became my Bus Named Sue.
Now to get on with finishing it.
