| Transmission Tmp gauge - should I ? where? [message #351440] |
Mon, 20 January 2020 06:53  |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
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I've always had a trans temp gauge in vehicles i was working hard. Most machines get warm right before they turn into a pile of scrap. Seems like a cheap warning that might reduce the cost.
So, has anyone installed one on the TH425? Has it been useful?
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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| Re: Transmission Tmp gauge - should I ? where? [message #351450 is a reply to message #351449] |
Mon, 20 January 2020 10:05  |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
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Thanks, that's impressive.
For now I am really digging the fact that all my original Stewart Warner gauges work. And they make a matching trans temp gauge that will fit right in. I'll probably relocate vacuum or amps off the main instrument cluster.
I'm not a luddite though. I like technology. I may look at a high temp alarm for the trans.
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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| Re: Transmission Tmp gauge - should I ? where? [message #351459 is a reply to message #351440] |
Mon, 20 January 2020 12:12 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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I use a Digipanel. My Mac dash (original opening fit) has a gauge but no sender connected. On my 'to do' list. Note that you can actually mount the digipanel out of sight - particularly if you've already got gauges either OEM or aftermarket working. The value is in the queeper (Sonalert) which makes enough racket to get you to look.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: Transmission Tmp gauge - should I ? where? [message #351461 is a reply to message #351441] |
Mon, 20 January 2020 12:19 |
6cuda6
Messages: 975
Registered: June 2019
Karma: -6
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Russell,
Is there an actual casting hole in the pan for the sender or did you add your own?
Russell K. wrote on Mon, 20 January 2020 08:10Dave,
Yes, a transmission temperature gauge is a good idea to monitor tranny temps and hopefully avoid burning up a transmission. Many GMCer's have installed tranny temp gauges. My tranny temp is monitored in the pan (ragusa). Others have installed a Tee in the cooling lines and monitor the temp there. I had to replace my gauge this past summer. Here is a link to my pics.
http://www.gmcmhphotos.com/photos/g7225-new-transmission-temperature-gauge.html
Safe Travels,
Russell
Rich Mondor,
Brockville, ON
77 Hughes 2600
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| Re: Transmission Tmp gauge - should I ? where? [message #351469 is a reply to message #351462] |
Mon, 20 January 2020 16:10 |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
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I'm not sure i want it at the pan. On my tow vehicles i always put it on the return line from the trans cooler. The idea being that you measire how well you are removing heat.
Does heat in the pan tell the story?
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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| Re: Transmission Tmp gauge - should I ? where? [message #351485 is a reply to message #351440] |
Tue, 21 January 2020 08:32 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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An external contact type thermistor sender is the only type I would consider. Plumbing in any sender adds a fail point, by the plumbing or the sender itself spewing hot oil (fire hazard). Similar type fail to Onan oil pressure switch which is common. Since the factory used a liquid to liquid cooler, I simply use coolant temp as a guide to trans temp.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Transmission Tmp gauge - should I ? where? [message #351487 is a reply to message #351440] |
Tue, 21 January 2020 08:44 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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John, on my coach, coolant temp only shows me what temperature coolant is going into the radiator. I use the transmission temp gauge to find out what temp is going into the transmission pump and hence the transmission works, particularly the clutches. Note that Tom Pryor has mounted a temp sensor at the output of the radiator which activates his cooling fan. That temp is relative to the transmission cooler temperature, but the transmission oil is probably a bit warmer.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: Transmission Tmp gauge - should I ? where? [message #351491 is a reply to message #351485] |
Tue, 21 January 2020 09:42 |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
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JohnL455 wrote on Tue, 21 January 2020 08:32 I simply use coolant temp as a guide to trans temp.
I'm thinking if the coolant is entering the radiator at, say, 210F, and it's returning to the engine at 190F then you might not know if the trans temp is climbing. Or, you won't know it until it goes past the point where the radiator can remove the heat.
For the price of another gauge, maybe i'd want to see the temp going in and going out? Probably overkill but i see transmission failure as the most disruptive thing that can happen.
- can't see it coming
- can't get parts quickly
- can't work on it myself
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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| Re: Transmission Tmp gauge - should I ? where? [message #351494 is a reply to message #351440] |
Tue, 21 January 2020 09:53 |
6cuda6
Messages: 975
Registered: June 2019
Karma: -6
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Not to steer this thread a bit sideways but what is the "ideal" trans operating temp of a 26' with 403. 26' with 455 and the same for the 23' units? I'm not a "gauge" guy but do see some value in having this one providing i know what i should be seeing on the gauge.....
Rich Mondor,
Brockville, ON
77 Hughes 2600
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| Re: Transmission Tmp gauge - should I ? where? [message #351495 is a reply to message #351494] |
Tue, 21 January 2020 10:15 |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
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6cuda6 wrote on Tue, 21 January 2020 09:53Not to steer this thread a bit sideways but what is the "ideal" trans operating temp of a 26' with 403. 26' with 455 and the same for the 23' units? I'm not a "gauge" guy but do see some value in having this one providing i know what i should be seeing on the gauge.....
Good question, so i did a search. The broad general rule across a bunch of transmissions, according to random people on car forums is 180-210 - same range as the engine.
And there is broad consensus that the cooler it is the longer it lasts.
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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| Re: Transmission Tmp gauge - should I ? where? [message #351507 is a reply to message #351440] |
Tue, 21 January 2020 17:23 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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My point is since it's a liquid to liquid heat exchanger, if the Dexron is much above 260F it would be boiling the coolant in contact with the heat exchanger in the right hand tank. Remember we only run at 9 PSI. If there is boiling you will be venting coolant to the overflow in short order and you've got bigger issues than your TH 425.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Transmission Tmp gauge - should I ? where? [message #351510 is a reply to message #351507] |
Wed, 22 January 2020 07:19 |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
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JohnL455 wrote on Tue, 21 January 2020 17:23My point is since it's a liquid to liquid heat exchanger, if the Dexron is much above 260F it would be boiling the coolant in contact with the heat exchanger
That's a really good point.
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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| Re: Transmission Tmp gauge - should I ? where? [message #351514 is a reply to message #351440] |
Wed, 22 January 2020 08:58 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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There are Dexron life vs temp charts on line. It's a sliding somewhat log scale where it is fine, then quickly degrades as temp exceeds threshold points. When it hits 305F it's pretty much done with zero time constant. The problem is measured average temp vs peak temps that SOME of the molecules are exceeding in key critical hot spot areas of the trans. Those oxidized molecules are then diluted into the fluid capacity. Eventually the fluid becomes overall darker. Hotter areas might be found in the converter, leaving the pump or sandwiched between friction materials during shifts.
John Lebetski
Woodstock, IL
77 Eleganza II
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