’56 Jetaway transmission problem

I have 1956 olds with a hydramatic jetaway transmission. I have had the car for a couple of months and have been driving her around on the weekends. Recently I noticed the car is having troubling shifting into second gear. It just doesn’t want to shift and will let the engine rev up too high before it roughly jumps into second. It is nothing awful, just noticeable and a little annoying. It doesn’t seem to do it as much in the higher gears. I have been forcing the car to shift by letting off the gas when I think the car should change gears. This seems to be working pretty well. Anyway before the problem gets any worse I wanted to find the cause. I was hoping it would be something simple to do with the carburetor. Or is it more likely a problem with the transmission itself? If it is the tranny, does this mean its time for a rebuild or is there an easier fix?

Thanks for the help and happy driving
-Anthony

Usually, I would say its a problem with the modulator . This is a simple replaceable device that relys on engine manifold vacuum to help tell the trans when to shift. Its stuck in one position, or the vacuum line going to it has either fallen off or has a hole in it.
That being said, I am not sure if this design actually has one. I will see if I can do a bit of research. If I find out anything new, I'll post an upate.