I am changing out my fan clutch in my 00 suburban. Long story short I bought the Hayden heavy duty unit from Oriely's and when I try to thread it on it strips the threads off the water pump shaft. There are two different types used on my year model, the heavy duty and the severe duty. Is there a chance mine came with the severe duty and that they had different threads?

 

So I went back and got the "severe duty" fan clutch and it worked. Based on everything that I had read, it appeared that they were going to be interchangeable but I guess not. I am guessing that since my suburban has rear ac and the towing package that constituted them putting on the severe duty fan clutch.