The TH350 in my 71 GMC was always slow to shift between gears. Exspecialy going into 3rd. I read that using FORD ATF instead of Dextron might help improve shifting. I dropped the pan and found some Shiny bits but not much at all considering the transmission is 47 years old. Results are impressive, crisp shifts now. I will update if I experience anything out of the ordinary.....
