2008 Tahoe - Windshield wipers started acting up. First they would move very slowly (at any setting), now not working at all. When I turn them on it attempts to move (1/8" or so) then it stops. Motor?

Possible wiper linkage has broken/seperated from wiper motor. The wiper cowling covering the linkage assembly will need to be removed to inspect/repair

because thats when your motor went or the motor was repaced in the wrong postion

You will need to find where in the linkage the problem is. I would start taking it apart to see what is and what isn't working correctly. Autozone website has free repair manuals available online.

Put the right side wiper on only. Turn on wipers. When the wiper moves all the way to the left and starts to go back to the right turn off the ignition with the wiper switch still on. Remove the right wiper arm and install the left wiper arm in the far left of the wiper movement. Turn on ignition and allow the left wiper to go all the way back to it's rest location at the bottom of the windshield. Turn off ignition and install the right side wiper arm. This will give you a start to properly set the wiper arms.

The windshield wiper circuit has an circuit breaker in it, under heavy load this breaker trips to protect the wiper motor, when the motor cools, the breaker resets automatically restoring proper wiper action.

the relay that runs the motor

Check the fuse for windshield wipers, that's the first point you can start looking for fixing the them.

The wiper arm could have worked up off the stem? mabey their is a set screw that worked loose that would keep it tight on the stem?

My tahoe has a plastic piece just to the left of the metal attaching arm. It is easiest to see on the driver side wiper. There is just enough room to slip a flat blade screw driver into and then pop upwards. After this clip is popped, slowly move the wiper blade to the right as you pull that clip further upward. The blade can now be removed. Of course if you have a different type blade this will not work.

its either the windsheild wiper switch, or the wiper moter....