So my 2003 Signature which I have owned since new, I was told by the main Allison dealer here in the Chicago area , needs to have a new transmission installed. (Ouch) The transmission is a Allison HD4000MH and the engine is a Cummins ISX525. My coach has 60k on it and I have always stored it indoors and heated indoors during the winter. I have the coach serviced regularly by my diesel mechanic and had the oil in the trans changed at least twice since owned. I know that the last time the trans oil was changed we installed "Transynd" . I have complained to my diesel mechanic that the trans temp seems to run high. I will see temps on the road for the Trans read on my digital readout get up around 240. Which is 40degrees+ higher than my engine temp. I will drive 65-68mph and see these temps. I was told that the reason for the high temp could be the location of the digital sensor, The digital sensor does read about 10 degrees higher then the dash analog trans sensor. I even had my regular mechanic clean - wash the radiator to help improve the cooling of the radiator/transcooler. To little to no help. So I have learned how to work with the hotter transmission. When outside air temp is hot and I am driving longer distances I will slow down 58-62mph. This would reduce the trans temp. If I end up in stop and go traffic I would shift trans to neutral as I coast or have to stop. This would help with cooling. Someone had suggested I take the coach to Allison to have the trans checked out. I made appt with Allison and they said it sounded like I needed the fluid and filter changed and I would be good. I told Allison my concern about the Trans temp and they said they will check it out after the service. After the fluid change they tell me the trans is still running hot. They need to yank the Radiator to check the cooling. They next tell me they didn't have to yank the Radiator, they were able to check the trans cooler and it works good. I get to speak to the Allison tech( who has worked there 20 years)and he tells me he has never seen a trans get this hot. Just an added note I have never noticed that the trans slips, runs out of gear or any performance problems. But breaking down on the road is the last thing I want to do. Anyone have any good thoughts or suggestions?