Mine does too and it drives me nuts. I think the clutches have 3 speeds. My thought is that it is engaging at full speed when it should be on low?

I also wonder about the water pump, any chance it could be getting worn out and not moving fluid fast enough allowing the system to run hot??

89 ext cab 22re 4x4 267K miles (for sale)
94 Land Cruiser Factory lockers
95 T100 4x4 ext cab