My 73 has a turbo 400. I just got it and it wont kick down into passing gear no matter what speed I'm going.
Any thoughts?

Down shifting is controlled by a switch on the accelerator pedal. There is a fuse, but I'm not sure where, so you should make sure there is power at the switch. Then there is a orange wire that runs from there to the side of the trans. Check to see if you have 12volts on the wire at the trans when you push the pedal to the floor. It is common for the switch to either break or not get pushed enough to activate it. If you have 12volts at the trans then the solenoid could be bad. Drop the pan and you will see where the wire goes to it. It is easy to replace.
You might want to check the cowl flapper door while you are checking the switch on the pedal. It is suppose to open when the pedal is flooded from the same switch.

You might also want to check the vacuum modulator on the passenger side of the trans. It's connected by a piece of tubing to the intake manifold. If the manifold vacuum changes, it can change your shift points. (I had this happen when I went to a high performance manifold.) You could possibly have a crack in the hose (or maybe a hole) that could be effecting vacuum. Good luck!!

My 73 passing gear did'nt work either.I had 12 volts at the switch and vacuum at the trans.I took the switch atop the gas pedal down and put a piece of 3/8 fuel line on the switch rod,so the switch had more movement cause there is no adjustment.There is 2 5/16 metal screws holding the switch inplace.Try this, this should do it, mine works great now.

Dave,Easton,PA

Thanks for all the feedback! I'll check them out and hopefully fix the problem.