97 gtp tranny problem

Car sat for 3 months, was fine before being parked. When i started driving it again it short-shifts second gear, and converter locks up. When downshifting it chatters. Changed fluid and filter, no change. Shows no codes. Has appx. 125,000 miles. It is supercharged. After it warms up and you drive it for about 10 miles it acts fine. Please help!!! Thanks.

Welcome to AF!!

You might want to add a can of Seafoam Trans additive to the fluid. This will clean the valves and clutches without damaging anything. Should make the trans work better.

thank you i will try this and let you know.