I'm running a Rotary works Gilmer pulley on my s4 t2 with an fd alternator. I've replaced the alternator pulley twice, if I drive the car for about 2 hrs, the pulley strips around the nut and becomes wobbley. The first time I put it on myself it lasted about 1 month. 2nd one was put on by alternator shop after they rebuilt the alternator, this one lasted maybe 50 miles. Someone point me in the right direction as to whats wrong

 

Sounds to me like the pulley from the alternator is cheap and bad manufacturing

 

I have a couple friends with it set up the exact same pulley. Only mine keeps breaking lol

 

use a lock washer??