Thanks. Stock trans cooler uses engine coolant to help get up to temp, but it's still just the little box down there catching whatever wind comes off the fan. X5 4.4 runs it's coolant at 108C which is 225F. I'll be changing that this spring - and I'll post how I do it with minimum of hassle, etc. Otherwise, thermostatically controlled or not, I would be surprised to see under 210+ trans temp on a hot summer day..............