Classic/Antique Car Repair: Passing gear, 66 impala, depressor

Question
Hello.

Last year I got my hands on a 66 Impala 4dr Sedan w/ a 350 block in it.

I have been doing alot of other work on it so this is something I only recently decided to investigate.

When I first drove it, the first couple months I had it, it seemed you only had to barely touch the gas for it to shift into passing gear.

Now, it seems it doesn't want to do it no matter what.

I am assuming I have the Aluminum Powerglide, it has a Carter 650CFM carb, and I can see and adjust the linkage that goes down to the tranny but don't want to mess anything up, so decided to ask before I break something.

Any ideas? Thanks!

Answer
you first need to make sure the passing gear linkage is operating and actually moving the shaft at the transmission. Second, make sure the normal foot "throw" on the gas pedal operates it. If all on that checks out,(which I doubt), run a string into the passenger compartment that is tied on the linkage depressor and take the car for a spin. See if you can "manually" shift the passing gear with it.

If all this fails, you have an internal problem such as lower band adjustment.