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Old 03-21-2021, 07:46 AM   #1
Winnebago Owner
 
Join Date: Sep 2020
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Transmission Temp - 2004 Meridian

Is there a way on this RV to monitor transmission temperature? I have a working FMC display, as well as a Scan Gauge D, but cannot locate any way to monitor the transmission temp.

Thinking about it right now, there may be a wa on the transmission selector, so I will dig in to that.

Can anyone suggest a "better way"?
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Old 03-25-2021, 10:01 AM   #2
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I use to monitor my temp on transmission on my LD E450 Ford chassis on a scan gauge. You tube should have the code. Or go to the Lazy Daze forum and obtain the code there. Travato John
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Old 03-25-2021, 11:26 AM   #3
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All you need to do is monitor the ATF level of the RV and look under it periodically to look for ATF leaks on the pavement. The flash point of ATF is 440 F degrees and I have never seen a temp reading even with heavy tow loads that exceeded 240F degrees. If your vehicle has a tow haul mode then use it when fully loaded or pulling a trailer as that will minimize ATF temperatures.
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Old 03-25-2021, 02:58 PM   #4
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My understanding is that transmission fluid breaks down with heat more so than with time. And that running above 200F is not advised.

I also know my engine thermostat is set for 180F and typically I motor down the highway at 183F water temperature and 160-170F transmission temperature, depending on how hot it is out side. (I have a 2004, Itasca Horizon 40AD with a ISC-350, and a deep pan Allison 3000MH tranny.)

And on hot days over 105F while climbing a 5-6% grade, with a toad behind me, my engine water temp can climb to 215F, and the tranny will slowly climb to 200. ...So I back off the peddle. And ever since I put an EGT (pyrometer) in my dash I also know to downshift the transmission a lot sooner than I used to. Also, I think my tranny temp commonly runs about -10F from my engine temperature if that helps.

===

Anyway, if you want to install a separate Transmission Temperature Gauge then you need to know more about the data bus the tranny sensor uses to pass this information along. (I think it's on the J1587 data bus, but I am not an expert in these matters.)

And somehow you probably want to know if your wire harness used in your Meridian is the same as used in my Horizon?

Note: I think the ECM does receive transmission temperature and then sends it to the gauge, but I don't know if this information goes thru the Medallion Message center or not?

Hopefully, your Medallion Message Center will have a wire harness with wires already there for a transmission temperature sender... and all you need to do is buy a salvaged transmission gauge out of an Horizon and connect it. Wouldn't that be nice!

OP: What chassis and engine is in your RV?

I have a an early model year 2004 Horizon 40AD (sold before April-2004) and FYI 2004 was a pivotal year for dash gauge control. I.e., my coach came with a VDC (located near the engine) vs late model 2004 Horizons that came with an MMDC (located under the dash).

Note: Both VDC and MMDC do essentially the same thing; so maybe you can look at my 2004 Horizon gauges (see pictures below) and then figure out how you can tap into your J1587 data bus so you can install a separate Transmission temperature gauge.

Question: Does your Scan-D pick up the J1587 bus? ...I'm guessing it does, but maybe the transmission temperature data is a customized protocol (by Freightliner) and that explains why you can see it on your Scan-D.

Anyway, now that you are armed with this information, maybe you can get a Level 2 Tech at Freightliner (800-Freighliner) to help you understand more about the J1587 data bus and where you can tap into your wires to install a separate tranny temp gauge? ...or maybe under your dash you will find a floating connector just waiting for you to come along and plug in a temperature gauge!

I thing the more you study the 2004 Horizon system the better you can understand what Meridian modifications you can make (if any). And again I'm assuming you have a Freightliner chassis.

Further, I don't know if it matters if your engine is a Cummins or a Cat, but it might.

Alternatively, you might be able to find a SCANNER that will tell you what your Transmission Temperature is on the J1587 data bus, but what good is that if you can't read it when driving on hot days... up a grade.

Doesn't that Scan-D product just interpret OBD2 Heavy Duty Truck Protocols? Does it read the J1587 bus?

I think the transmission temperature information you are looking for is found the J1587 data bus, which talks to the 1939 data bus which talks to the ECM and your OBD2 port specific for Heavy Duty Truck applications. (Not to be confused with OBD2 ports or scanners used on cars.)

OP: Do you have any concerns your tranny fluid is burned?
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Old 03-25-2021, 03:44 PM   #5
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...Or you can install a GlowShift Transmission Temperature Gauge if you can find an access port to your Allison you can tap into... and you don't mind having a separate instrument cluster.

...Maybe then will be a good time to add an EGT-Pyrometer; and if you have a Cummins-CAPS injection system, I would also add a FASS or AirDog Electric Fuel pump and bypass that CAPS Lift Pump, which is a real priority if you ask me!

Here's a video on how this person added a Transmission Temp Sensor for cheap:

And below is where I added some gauges next to my left knee. And BTW, you do want these gauges to be lower so the lights don't bother you at night.
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Old 03-25-2021, 07:33 PM   #6
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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
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