ou812sm

iTrader: (16)

6l80 or 6l90 and what's the difference between the two

05GMC4.8

The 6l90 came in the hd trucks and is a little beefier... similar to the 4l60 vs 4l80. Not sure if they have different gear ratios tho like the 4 speeds did. Pretty sure theres at least a couple threads about this already on here too. Try the search button.

Mike @ New Era

iTrader: (10)

It has a 6L80. The 6L90 has an extra clutch in the 2-6, 3-5-R, and 4-5-6 clutch packs.

Blackpanther99

iTrader: (8)

That^ I have a 6l80e, but not a Denali lol