Cold shift issues are usually modulator related. Try this.
Hi Everyone,
My obsessive compulsive nature won't let me stop working on this car. I'm sick. Anyway, I wanted to share something I have learned that might be helpful.
Ever since I got this car, it never really shifted right (auto). Because I have been working on so many different things, I never got around to it, but this weekend I finally took the modulator valve off the transmission, just to take a look. I discovered that the piston inside was pretty well jammed up inside and not responding to the vacuum signal. I took the vacuum diaphragm off the lower piston valving assembly by removing the four philips screws. I used a vise to hold the modulator and carefully, without stripping the heads, got them loose. After getting that off, I was able to get the piston out by carefully prying it up with a mini screwdriver in two steps, first from the lower chamber of the housing, then up in the higher hydraulic chamber, I could push it a little higher. Then I had to bang it on the workbench to get it to fall out. Once everything was apart, I wet sanded with 2200 paper soaked in transmission fluid both the piston, and the bore. Roll the paper up and push it in the bore to sand. Once I got done polishing it, the piston popped up and down freely on it's spring, which you will see come out with the piston. It sits in the bottom. Put the vacuum actuator back on, put the car back together, shifts like a champ! If anyone wants clarification. let me know
