The drivers side wiper on my 72 Riviera seems to be out of alignment it goes off the edge of the windshield when they are running it also fails to go all the way down below the hood level when you turn them off. The passenger side seems fine. Also this may be related or not but every so often the drivers wiper will decide to take about six inches off each end of its travel when on and go a bit slower (maybe hard to tell if its really slower but seems it). Turning the wipers off and back on again makes it go back to normal.
There is nylon bushings in the joints and pivot points of the wiper transmission assembly. Its all under the cowl screen. sort of a pain to get into. Most Likely worn out.
