wolfe10 wrote:
hzjcm8 wrote:
mci7 wrote:
Reference to the 4000MHR transmission, using the Detroit TranSynd oil, What would the max safe temp allowed when decending a mountain using the retarder ?
So far, have not let it go above 220F.
Many thanks
MCI7,
I would say you could let it get to 250F but only intermittently. The transmission will allow a max "converter out" temperature of 330F so 220F sump temperature is not too high. The transmission will go into the "inhibit" mode to allow better cooling once it reaches a pre-set sump temperature but I'm not sure what that point is. I'm thinking it's probably around 250F though.
Tom,
Let's back up a minute. There are three different (very different) location for the transmission temperature senders on RV's I have worked on. I have seen them at the transmission sump, line into the transmission cooler and the line out of the transmission cooler.
Each will have a maximum recommended temperature, with the sump temperature likely being the most "accurate" and critical in reflecting what is happening in the transmission.
If you could share temps for each of these locations, it would be of assistance, as the readings are so different.
mci7,
Converter out ("To Cooler") will be the highest temperature. Allison allows 330F max converter out temperature before the electronics will inhibit functionality to try to cool the transmission. Sump will be typically between 180F and 220F. The lowest temperature should be "From Cooler". The temperature drop across the cooler is dependent upon air flow, surface area and cooler flow. I would pay the most attention to the sump temperature since it is a function of the cooler circuit design and flow. It should be the most stable since cooler in and cooler out temperatures vary more depending on how much you operate in converter mode vs. lockup mode and have less of a "heat sink" affect meaning the heat disipation rate (heat transfer) will be more efficient in the smaller mass of the converter in and out sensors.
I really can't give you much info on typical cooler in and out temperatures.
