66 mustang Speedo conversion 289 V-8 C-4 Automatic Trans

Put a set of electric gauge set From new vintage also got the 16 pulse generator to put in the trans for the speedometer when i had the cable drive stet up in there with the manual speedometer had bad Bounce put new gears and cable worked for a while and than also got bad bounce. So i switched to all electric gauges and Speedometer but now the pulse generator and the Speedo is not working speedometer does nothing gauge lights up other functions work fine Any Ideas here could the gear on the tail shaft be bad ??? please give me what you come up with
THANK YOU
Clyde