motohead911

iTrader: (1)

I just swapped a 6l80 into my Silverado last week and I am having an issue with the factory 6l90 tune in it right now. In normal mode it works great, but when I put it in tow haul it doesnt seem to want to up shift. If I am driving along it will shift all the way up to 4th then immediately downshift into 3rd and stay there. I have been doing some reseach and it acting like it is going into shift stabilization mode. Does anyone have any ideas how to get it out of that mode, short off turning off tow haul mode. I really like to grade braking function of the tune I have in it.

Wolftrk99

iTrader: (5)

It could be an issue with the 6l80 with a 6l90 tune... The trans are setup slightly differently intrenally so it could actually be expecting line pressure to be x and seeing y..... 6l90 has more clutches and a different planetaryand one or two more checkballs in the valve body....