My fan clutch almost made it to 100K, same scenario. Coolant did not rise but due to decreased CFM's through cores the A/T did. I used NAPA P/N 272313 lifetime warranty (NOT a product endorsement, just the facts - do not work for NAPA or their affiliates). It looked to me to be built better than the OEM, which per Cummins, it not a Cummins part and not available there. Has been above 95¥ here recently, Starting from a light I sound like Midway until I reach about 1500 RPM, then the air chill apparently shuttles the clutch - smoothly, not abruptly. Getting the old one off is fun - keep the belt in place and use impact (punch, wrench, hammer) to loosen the nut - a BFW and gently torque won't do it. Remember Left-hand thread!! I Never-seized the new one just in case. As far as locking the fan in completely, maybe it won't matter at our engine speed ranges, but doesn't a fan clutch disengage based on temperature and/or centrifugal force?? What happens if you overspeed a non-flex fan???