I recently rebuilt my (1951 3100) wiper system with all new rubbers and cleaned out my vaccum motor and lubed it. When i hook the vacuum motor up to the engine with no linkage attached it works fine and takes quite a bit of force to stop it from moving. When i hook it up to the wipers it barely moves them even when reving the engine. Based on how the motor preformed im thinking that some of the new rubber in the wiper linkage is causing extra friction, mainly where the hex on the motor swing arm enters the linkage. Are the hexes supposed to rotate because mine do not and the rubber is a tight fit on it which doesnt make much sense to me. Also are there any other spots that i could lubricte the linkage.

P.s. this is a fair weather car
that i want to keep original as possible. So electric is a last resort.