You will not find a woodruff key slot on any car alternator that i have seen or in the pulley either. Make sure the pulley is a good fit on the shaft,that it has not worn the shaft or pulley from being loose.When you are sure the fit is good(it should push on by hand but once it is all the way on NO perceptable play between shaft and pulley) The best way is with an impact wrench but if you dont have access to one you can use a box wrench for the big nut and an allen wrench in the end of the shaft to keep it from turning,get it as tight as you can and then check it againg after a few miles. Don

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Red Green "This is only temporary,Unless it works!"

97 E300D 157000 miles
87 300TD ?141k? miles