I'm having a strange problem where after my Falcon has sat for a while, it won't shift from 1st into 2nd until it's been driven for several miles. It just stays in first gear and revs really high. I've tried manually shifting to L and then back to D, and it still won't shift. After a while it will eventually decide it is ready to start shifting like it should be. Another issue that may be related is I have had it slip from second down to first and then rapidly shift back to second again every now and then. I drained all the fluid, and replaced it with Type F, and have made sure fluid level is correct. It looks like the vacuum modulator on the rear of the transmission has been replaced by the previous owner. Anyone have any suggestions on adjustments I can try?
You have a 2 speed aluminum transmission.
Given the age internal seals are probably hardened and shrunk.
Getting parts may be quite a chore.
Nothing other than adjust the bands is possible.