Well if your vacuum was way the heck off, your car would act like it was floored all the time and never shift into high. Similar to the kickdown being stuck on, which could also be the problem. You should check the inspection hole on the tunnel to look at the solenoid on top of the tranny to make sure it clicks into it's three positions properly: Idle, Floored, and Everything in between.

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1967 230S automatic
Boston, MA