I called a Toro dealer yesterday and spoke w/one of their technicians. He told me they have an updated fan clutch thats supposed to make the fan sound like a jet engine when it locks up fully. Here is the part number in case anybodies interested. 115-1562. I'm going to see if there is a reverse fan blade as well. Since we service all the equipment for L.A. city golf courses, there's a lot of fine garbage that restricts these screens in front of the radiators. Especially if its dry grass clippings. I'll post my results when I get the fan clutch. This is either an engineering issue (i.e. radiator not large enough, not enough air flow, coolant flow speed). If replacing the fan and clutch doesn't work, and this thing is moving massive amounts of air across the radiator....then the problem has to be in the radiator itself (airflow restriction, radiator not large enough, not efficient enough of a design) or in how fast the coolant is flowing in and out of the radiator.