It sounds like one of the "pins" on the bar is missing if a nail is being used to hold the transmission on. If you aren't comfortable with that, you need a new motor or yours repaired by having the bar replaced.
On the vacuum wiper motor, the transmissions are held on by a single spring approx 2 1/2" long that has eyelets on both ends and when installed it stretches between the 2 "pins" on the bar. The 2 pins are grooved for the eyelets to ride in keeping the spring from moving up or down the pins. It slips on over the arms and the tension will hold the arms on.
The part that shown on the American Classic page is for electric wiper motors.
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Last edited by Cablesmill; 04/27/2016 10:49 PM.
