Remove your Governor and make sure it is working. I had one where the pin on the shaft broke and the gear just turned in place.
To test the governor secure it in a vise and insert the shaft in a drill motor. Hook up an ohm meter, one wire to the contact and the other to ground. Spin it up and it should peg the meter. If not its not working.
Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine