Does a Chevy 2500 with 6.0 vortec engine come the Allison transmission?
No, a Chevy 2500 with the 6.0L Vortec engine did *not* come with the Allison transmission. The Allison transmission was typically paired with the Duramax diesel engines in the 2500HD series. The 6.0L Vortec gas engine used a different, heavier-duty automatic transmission, usually a 4L80E or a 4L85E.