I forgot to mention my 2004 Itasca Horizon 40AD came with a TripTek System that provides a digital readout of your engine sensors -- including the Transmission Temperature.
The TripTek plugs in behind the dash and reads the ECM, Transmission Data Center, and VDC/MMDC so it can output those readings to a digital display.
Coretronics makes "TripTek" but they are longer supporting this system. Still, I think you can reach someone in tech support (Larry seems to be the name I remember, but that's a long shot)... but someone there will know all about the 2004 data bus used by Freightliner and how the TripTek System uses this data.
Note: My tranny temp gauge is sourced through Freightliner, but the TripTek device displays the same digital information on its display.
Here's some more info in my tech library that may help you pursue this.
Coretronics, Inc Trip
Tek Motor Coach Computer & Smart Tire Pressure Monitoring
http://www.triptek.net/trouble.html 1/1
1251 E. Iron Eagle Dr.
Eagle, Idaho 83616
Ph: 208,938.6331
http://www.triptek.net/triptek.html
KEY PART NUMBER U/M DESCRIPTION
1 143591-02-000 EA
WIRE LOOM - COMPUTER TRIP/ENGINE MONITOR-TRIP TEK 02-04007
2 143591-05-000 EA COMPUTER - TRIP/ENGINE MONITOR - F/COLOR MONITOR - #2500-3 (SERIES 2500-3)
3 143591-04-000 EA CABLE - CAMERA INTERFACE - F/COLOR MONITOR