I replaced the wiper motor on my '56 a few years ago with a rebuilt unit from Macs, I installed this unit and everything was fine was able to slow the wiper arms down to almost barly moving which was great.  After the first year of little use since I dont drive the car much in the rain but I do try to run the wipers for a little with some water on the windshield to use it from time to time, but this didnt help as after the first year the wiper motor slowed down where its no where near as fast as it was when I installed it.  Now this is the third year and it is a little slower than last year but the new issue is when switching the motor off the arms just hang in the up position as you hear the vacuum slowly venting.  It took running the wipers for about 5 minutes straight to get it to park a bit quicker but it still takes some 30 seconds to vent the vacuum before the arms park on their own.

I believe there has to be some kind of service that I havent done on this motor and my original shop manual says its a whole unit and doesnt make mention of servicing or repairing the unit and my owners manual makes no mention of servicing the wiper motor but it does make mention of servicing the clock.

So my question is what kind of service should I be doing on this wiper motor to get it back in proper working order?

I did some online reading and some have said clean the old grease out and apply new grease when this starts happening, some say to put some ATF or brake fluid in the unit and it will soften the leather seal back up and make everything work smooth again.  I dont know what to do in this case cause this is a rebuilt unit I got from macs some 3 years ago and I dont believe the leather seal could have dried out in 3 years and I dont know if there is grease in the unit or not from the rebuild.  I also hate taking the unit apart cause with 3 years I just know the gaskets will most likely rip apart trying to disassemble the unit.

1956 Ford Fairlane Town Sedan - 292 Y8 - Ford-O-Matic - 155,000 mi