I’d go with @Best4x4 and get one from a parts store. I ordered mine from Rock Auto and they did not come with hardware.

they are threaded so no lock nuts needed. What I found really irritating was that the severe duty and heavy duty clutches had different thread pitch holes and they were a different depth as well... Try to find one with hardware included and save yourself the trouble. Then it’s a super easy project.

 

FWIW I installed the Hayden 2991 Severe Duty fan clutch about a year and a half ago and just re-used the original bolts.

What's weird is that the cooling results are not as good as they were with the 20-year old fan clutch I replaced only because I was replacing the water pump.

I have the gray 180° thermostat in the truck, so cruising temps are generally 188.6° F, but before replacing the fan clutch the truck rarely got above 194° at stoplights. Now it's common for idle temps to get to ~204°, regardless of ambient temps. Not a problem, I know, but surprising to me. One of these days I may reinstall the original fan clutch and see what happens.

 

I'm sure you already know but that can happen with a tiny bit of air in the system. Have you double checked your bleed through the hole in the T? Again assuming you aren't running the inline mod.

 

There's no air in the system. It's well-bled, but thanks. Besides, a little air in the system wouldn't produce the results I described.

In fact, maybe I'll introduce a little air into the system to prove the point.

 

planning to order the 2781 heavy duty clutch this week. does anyone know what bolts to order? Planning to order from rock auto.