Jake Brake or Transmission Retarder, or Both

[davidbrady]

Ernie,

Heat is definitely an issue with the retarder. My H3 has a huge transmission cooler plumbed just upstream of the S60 water pump. With the retarder on, when the transmission fluid hits around 230 deg F the S60 radiator fan comes on which gives the system a lot of head room to absorb additional heat. I can say I Death Valley tested the system on my way home from Kamloops CN. I entered Death Valley on the west end and descended from 8500 ft to -200ft below sea level in about 3 miles and in 100+ deg F ambient temperature. It was a challenge to keep the transmission fluid below 250 deg F which is the point at which the Allison will throw a code. At one point I had to pull off the road to let things cool down. So, you do have to watch the temps on long steep descents.