Originally Posted by herk7769
I have the Allison transmission option with my Duramax (it is ONLY available on the diesel). I LOVE IT.
Although a very expensive option when I ordered the truck (my dealer had NEVER ordered it "for the lot" before because of that), the trans shifts flawlessly and has an external filter that can be changed easily (even after every long trip if you want to since its a spin on). Tow/Haul mode uses all six gears (just changes the shift profile for when the shift occurs) and up/down shifts automatically for best uphill and downhill speed control. The top two gears are OVERDRIVE gears and we get pretty good fuel mileage hitched or not (though do NOT buy it for fuel economy as it is not much better than the stock 6 speed auto trans and the break even would be several lifetimes).
The Allison trannys are just about bulletproof as long as you maintain them properly. I just wish they were rated for a bit more torque because you can only add around 70-80 additional HP to the motor (easily done with any programmer) before you begin to shorten the life of a stock Allison 1000. If you build them with HD clutches, it's almost sky's the limit for torque capability. Still love the Duramax/Allison combo though!