[Richard]

The tranny temp increasing going down a long grade with the jake makes sense. The torque converter is acting as the brakes.

Your engine temp is a bit high according to the DD info on the thermostat operation for a series 60. The spec sheet I have says the thermostats close at 196 and fully open at 204. Your low engine temps at normal and high at temps under load do raise curiosity questions about what could cause that