1999 Chevy Silverado windshield wiper

one motor runs both wipers. if the wiper is seated on the wiper transmission, then you either have linkage popped apart under cowling or the wiper is stripped where it fits on the wiper transmission. remove the entire wiper arm and see if the transmission sticking out of the cowling is turning. if it is, check the hole on the wiper arm and see if it is stripped. if the transmission is not turning, you have linkage that has popped apart or broken. remove cowling and see what the problem is. good luck