Allison 6 speed

[RJones]

How are the Allison 6 speeds holding up? I want to upgrade my 2006 Duramax but I don't know how far I can go without upgrading the trans. The truck is is for daily driving and may see moderate trailer loads. Comments will be
appreciated.

[JohnC]

I don't have that many miles on mine, but I can tell you the guts are the same as the 5 speeds, for all practical purposes. The 6th gear is just a different combination of clutches.

[NutNbutGMC]

I don't have that many miles on mine, but I can tell you the guts are the same as the 5 speeds, for all practical purposes. The 6th gear is just a different combination of clutches.That, resulting in a taller gear with less RPM, or a levelized use of the gears there. The 6-speed is nice as such, but it's nothing entirely special over the 5-speed. I've had both. The 6-speed is as solid as the 5-speed, in my opinion.

$0.02.