Background:

102k on the original 4L60E
The car sat for a year, no trouble with transmission before .

Symptoms:

Rough shifts
Slips @ WOT

Solution:

Slick 50 High Mileage Transmission Treatment

Poured a bottle of this stuff in (took 10 minutes) and walla shifts are easier and the slip seems to have disappeared. I don't know if this is a bandaid or not but it worked so far. I hope the year it sat has something to do with this and not any major problems were just temporarily fixed. What do you pros think?

 

I have used that stuff a couple times and was amazed it can do magic at times , stinks though , seems to really help when a trans has been setting and is acting up