I am still on the fence with my Trans. Retarder. I was not using it correctly to begin with, and then when i knew more about it and the Heat issue , I became more frugel.
Troy at Liberty said I would really enjoy having the Retarder, and I can say it works great on off Ramps, Stop Signs, and Stop and Go Traffic, and emergency stops.
On down grades, I brake to about 55 or 50 MPH and then apply the Trans Retarder to the 1st or 2nd position. I then cruise until the speed exceeds 60 to 62 MPH , then I brake again and start the process over agan.
I leave it off most of the time except on grades.
The temperature climbs to 290 on long downhill grades.