Wiper problems

Just replaced the wiper transmission on daughter's 99 Sil....Not sure what i'm doing wrong, butwhen we try it out, it catches somewhere and losens the bolt holding it on the motor shaft.Sprayed lube on the linkage's as they seemed tight when working by hand...Still do but will work if worked hard.Could they be the cause?Thanks Oh, That L- shaped bracket that the switch thingie needs 4-6mm setting is worn. So I bent it out and up more with pliers until it caught better as the switch came around.