Cruise-O-Matic installed in a '63 Thunderbird, trailer queen. When the car was restored, the transmission was rebuilt, shift kit installed, and functioned fine for two years with intermittent use, driving on and off trailer and onto the show field 5-6 times per year. This year while tuning the carbs with the car in park, it felt like the engine did not want to accelerate. Though I didn't realize it right away, it turned out that the engine was in gear and park at the same time. When the car was eventually backed out of the garage, it would not move forward in any gear - reverse was still engaged. If the car was shut off and restarted, the car would move forward in D1 ( felt like it was starting in second gear), but if reverse was engaged the trans would again lock up when moved to D1, D2, or L. Took the trans out, removed the shift kit and noticed that the holes in the original plate did not match up at all with those in the shift kit, and thought that may have introduced a cross leak, so replaced the new plate with the original. Clutches had all been burned up and new packs were installed, trans cleaned etc.
Installed the trans back in the car and now it goes into reverse and drive (D1, D2, and L) just fine, but it won't upshift to 2nd gear unless manually shifted from D1 to D2, and then there is no 2-3 shift. If manually shifted from D2 to D1, it slams back into 1st gear and won't upshift. When starting out in D2, it starts in second, but won't upshift to third. All gears, R, D1, D2, and L initially engage very smoothly, doesn't slam into gear at all. There is good vacuum at the modulator and the line is connected. Shift linkage and manual downshift linkage have been adjusted, checked, and rechecked are functioning correctly. Could the modulator (which was installed new at the initial rebuild) have gone bad already? Governor problem? The car has been test driven about a mile so far with no change in the initial symptoms.