Looking in hindsight, I probably should have picked up on the fan clutch failing. Wife had been complaining about transmission hunting at highway speeds. When it did drop down a gear you would hear the roar of the locked up fan. Internet searches produced tons of complaints about the 4R transmission hunting. It’s my wife’s truck, so I don’t drive it much. When I did drive it down from Montana to SoCal in early September, it only happened a couple times, so I dismissed it as normal.
I have never seen this happen and I work on all sorts of vehicles. Currently own 5 vehicles, including two K2500 Suburban 6.5 diesels, both of which have upgraded water pumps, fan clutches and fans from the early Duramax to enhance cooling. Those fan clutches will come on infrequently, but the fan roars when it does. The fan blades are fiber infused black plastic riveted or bolted to a metal hub. It’s a much more robust build than the Toyota which uses a blade one would expect to see on an electric fan.
So I feel like this is on me and I’m not happy. I drank a bottle of Napa Cabernet with my NY Steak and wild rice last night. Should be pulling a manual transmission from my Honda Accord today, but watching football instead.