They did give me the thicker severe duty model which is what the truck had originally.
I've learned quite a bit about clutch fans in the last day or two. It looks like there are two models, heavy duty and severe duty, that would fit my truck with a 3.73 getting a severe duty and 3.42 getting heavy duty. The bolt patterns are the same but the severe duty is noticably thicker. Both my 93 and 94 GMT400's are 3.73 and the factory original clutch was the severe duty model on both. My 93 still has the factory original as far as I can tell. It makes no noticalbe fan noise and neither did the factory clutch on my 94. I replaced the 94 clutch last winter because the bearing was shot and the clutch started wobbling and making noise. On the 93 the factory orignal clutch is stiff when cold if it has been sitting but if you spin it by hand for a minute or so it loosens up quite a bit. The Hayden severe duty I now have on the 94 never loosens up, it is always really stiff, even after driving it down the highway today on a cool day (when the clutch should not have been engaging much) it is really stiff. I went to the parts store and looked at the other model, the heavy duty. I spun it by hand for a minite and it loosened up a lot, like my factory orignal severe duty model on the 93. I'm going to see if Advance will swap my the malfunctioing severe duty for a heavy duty. I dont ever tow and I line in northern MN where it donest get really hot so I dont need a severe duty one anyway. I sure hope this fixes it. I have to run it in OD at any speed over 45 unless I want to go deaf. Anthing over about 2500 RPM sounds like an ariplane and every time you start out from a spot sign the shift points are in the high 2000's so this drives my nuts. What really puzzles me is the the first Hayden severe duty clutch I got last winter to repalce my factory orignal initally only made the fan roar for a few minutes when it was cold and had been sitting a while. I could live with that but it seemed to get worse over time until recently the roar never stopped. The second Hayden severe duty I just got the other day had the fan roar all the time from day one and now has about 100 miles on it and no change.
