Recently went through this on 67 Gtx, 2 /s wiper , no park ! On the motor you will see round plastic cover , mark two reference marks if never removed , then take wires loose, remove this cover , watch out for the big oring seal , and clean and sand brass points well but gently! Reinstall, using your reference marks ! There is a decent explanation of the points operation, in the FSM ! If this cover has been previously removed, you may have to adjust it some what ! Oh , forgot, what I found under the cover is a plastic cam which engages the large driven gear to cause the points to cause a park effect! Not making sufficient contact between this cam and the appropriate spot on the driven gear , gently pushed pin in center of white cover out saving the small retainer clip and found thin spring washers collapsed, cleaned up used white lube and polished stainless washed to reshim , placed retainer clip back on ! Reinstalled correctly! And the sucker works like new , after adjustment for correct park position ! Be careful, none of these parts are available, but some repair guys have the cover , but are very proud of them ! If I can help you more , pm me ! JC
