Community Forums

ricksue · 11-24-2020, 11:05 PM

I have an Allison/Cummins ISL combination (2003 and I notice that my transmission temp gauge hardly moves. Regardless of outside temp or climbing a hilll it rests on around 150 degrees. Once when stopped at a very long traffic signal with the trans in D, I did notice it move up a little so I am assuming the gauge works. Is it just a matter of calibration? Should I be concerned?
ricksue

CountryB · 11-25-2020, 05:26 AM

On my Coach the transmission temperature "dash gauge" has its own sender unit mounted on the transmission cooler hose at the rear of transmission. You doint say what model/make Coach you have, but for a 2003, I think your coach would be the same. You can test the wiring and gauge by disconnecting the temp sensor wire at the transmission and with the wire disconnected the gauge should peg out(cold) - then ground the wire and the gauge should peg out in the other direction (full hot). If it does that then the wiring and gauge are okay and the sensor is bad.

I had to replace my sender unit once already. But I consider the dash gauge jut to be ornamental. I don't rely on it for accurate information.

The trans temperature that the computer sees is from an internal sensor in the transmission and the most accurate way to monitor temps.

If you don't have engine/trans data monitoring (like with a Silverleaf or Aladdin or such) you can add a "Scan Gauge D" display unit. It plugs into the engine/trans diagnostic plug under the dash and gives you the readings that the ECM sees. Then you will see the "actual" trans temp, engine temps, ect., and it reads fault codes.
https://www.scangauge.com/products/scangauge-d/

TowDawg · 11-25-2020, 06:31 AM

Mine stays pretty constant about 165, but I added the Scangauge display module that CountryB mentioned because my speedometer was off by a good bit and my oil pressure gauge quit working as well. Trying to find replacement gauges that match, with the correct resistance settings to be accurate was a nightmare, so I went with Scangauge and have it set to show water temp, trans temp, speed, and oil pressure.
Not only was it easier, but it's whole lot more accurate than the typical analog gauges.

flamebuster · 11-25-2020, 06:47 PM

The reason the gauge hardly moves is because Monaco uses a sending unit that reads as high as 450 degrees. The reason for this is because it is the only sending unit made that is flush with the bottom threads of the sending unit.. I think they were worried if they installed a sending unit that the probe hung below the threads it would restrict the oil flow in the main oil line to the cooler..
I replaced mine with a Stuwart Warner 245 degree sending unit and now the needle moves to just under halfway of the gauge, very much similar to the engine temp gauge.. It is at least more reliable if the trans. should ever start to get hot.. My Aladin says the trans. temp is around the 165 degrees at normal operating temps.. Also I say no increase in operating temps. with the longer probe sticking in the oil flow according to the readout on the Aladin.
I will try and look thru my records and see if I have part# for the SW. sending unit.. There was a post on here earlier this summer on the same subject that with it's photos explains it much better than I am able too.

flamebuster · 11-25-2020, 06:53 PM

https://www.irv2.com/forums/f125/tem...er-267331.html Here is a link to a discussion on the sending unit location you are looking for post #4 is a photo of the sending unit in the large trans. cooler line..

96 Wideglide · 11-25-2020, 07:08 PM

Quote:

Originally Posted by flamebuster

The reason the gauge hardly moves is because Monaco uses a sending unit that reads as high as 450 degrees. The reason for this is because it is the only sending unit made that is flush with the bottom threads of the sending unit..

Makes sense!
If I want to see my actual trans temp, I bring up the Aladdin screen.

And to the OP, what you are see'ing when sitting in traffic, or crawling along in drive is real. Lot's of heat in your transmission in these conditions with the torque converter slipping. If possible, put your transmission in neutral.

flamebuster · 11-26-2020, 11:09 AM

Ok slap me silly...

After I looked thru my records the sending units are VDO. German made, the original sending unit installed by Monaco is part# VDO 323-086, it is a 400 deg. unit.. I switched to part # VDO 323-057 it is a 300 deg. unit... I had tried a lower temp unit VDO 323 -500 which is a 240 deg. but it made the gauge read higher than I wanted, they do show a variety of temp.s in their selection but you will need a 1/8" 27. thread body the wire connection is easily changed if you choose a threaded stud style.
I am quite happy with the 300 temp. range unit...
You can get these thru a automotive supplier such as Napa or Jeggs, Amazon etc. Roughly in the $20.00 range.