Transmission temps.

[Oh-one]

While using the engine brake on a long 6% grade the transmission temp. when high( 212deg). What is the design temps for such operation? Afterward the temp came down to 199. At what point is the temp considered too high?

[EngineerMike]

Allison should be good to near 240.

[dbarton291]

Quote:

Originally Posted by Oh-one While using the engine brake on a long 6% grade the transmission temp. when high( 212deg). What is the design temps for such operation? Afterward the temp came down to 199. At what point is the temp considered too high?

Actually, it depends on where you're reading the temp. The max to cooler temp allowed is 300 deg F. Output retarder models are allowed to hit 330 intermittently.

Max sump is 250 deg F.

Remember though, heat is one of oil's enemies. The more you run at elevated temps, the shorter the oil life. In an oil to water cooler system, the trans oil temp with run close to engine water temp after the cooler and slightly elevated before.

[Crusingator]

According to Allison the MH3000 normal operating temperature is 140 to 220 degrees F. This is also what is programmed into the OLS oil level sensor, any thing below 140 and you get a oil temperature too low code and any thing above 220 you get a oil temperature too high code.

[dbarton291]

Quote:

Originally Posted by Crusingator According to Allison the MH3000 normal operating temperature is 140 to 220 degrees F. This is also what is programmed into the OLS oil level sensor, any thing below 140 and you get a oil temperature too low code and any thing above 220 you get a oil temperature too high code.

http://www.allisontransmission.com/s...t=OM3349EN.pdf

Here's a link to the Allison MH series operator's manual. It lists the various temperatures published for normal operation, checking oil using the OLS, etc. Page 52 lists the max temps I quoted above.

Be careful not to confuse max temps with the temperature range the oil level sensor operates in, or "to cooler" temperatures with sump temperatures.

[Techie]

FYI -- if you need to know the exact temps you will probably have to have an Allison dealer compare the the internal readings to your gauges. When I recently had my 3-yr service I asked as our "normal" temp on the trans (vis Silverleaf) is 220 +/- 5 and we have hit 240 on more than one occasion; our dash gauge has hit 300 which we believe is the sump output. WHen they did the service they checked and our fluids were fine, the trans never reported a temp problem and they told me that the temp sensor that they use was not the same as either where our analog dash guage or our Silverleaf read from...so go figure!

[Crusingator]

I am a user of the VMSpc program from Silverleaf Electronics. This is my third chassis I have used the program with. My 2002 Freightliner chassis with the system III electronics package would report the Allison transmission oil temperature, transmission output shaft speed as well as the gear attained and gear selected. All of this was reported on the SAE J1587 protocol and the J1939 protocol.
When Allison upgraded its software to the next generation it reported ONLY to the J1939 protocol. The VMSpc software can ONLY listen to the broadcast of the J1587 protocol. So since the VMSpc CAN NO LONGER listen to the NEW GENERATION Allison transmission I no longer can display that information on my PC.
However, the Freightliner XCR chassis with the MMDC and the LBCU can read the information from the databus and display it on its screen. The various engine, transmission, ABS and other systems which report on the J1939 databus ALL use the same sensors. One of the three lines I monitor on my LBCU is the transmission oil temperature. That temperature is reported by the Allison oil temperature sensor in the transmission to the J1939 databus.

[dbarton291]

The trans temp reported on the datalink is the sump temperature. That's where the temp sensor that's part of the transmission control system is located.

Dash gauges are normally, but not always, hooked to temp sensors in the transmission cooling system. These temp sensors should be in the "to cooler" line, which is the hottest point in the system for transmission fluid.

The sump temp should always be cooler than the "to cooler" reading because the fluid passes through the cooler on its way back to the sump.

Crus: What do you mean the various vehicle systems all use the same sensors?

[Crusingator]

When Allison connects their laptop to the transmission it is accessing the same sensors which report on the ASE J1939 databus. Now I have no doubt that Allisons software has the capability to access more information (sensors) then what is reported on the J1939 databus. I am just saying the oil temperature sensor that is reporting to the J1939 databus can be read and displayed by any instrument capable of reading that databus. And they will all get the same information. I agree IF the oil temperature sensor reporting to the J1939 databus was installed after the torque convertor the temperature would be higher.

[dbarton291]

Quote:

Originally Posted by Crusingator When Allison connects their laptop to the transmission it is accessing the same sensors which report on the ASE J1939 databus. Now I have no doubt that Allisons software has the capability to access more information (sensors) then what is reported on the J1939 databus. I am just saying the oil temperature sensor that is reporting to the J1939 databus can be read and displayed by any instrument capable of reading that databus. And they will all get the same information. I agree IF the oil temperature sensor reporting to the J1939 databus was installed after the torque convertor the temperature would be higher.

I see what you mean now. You are correct any instrument capable of reading the SAE J1939 databus will read the same sensor info Allison DOC will. What's on the databus is the sump temperature. That sensor is part of the transmission control system.

The temp sensors that are typically installed by the OEM or an end user in the "to cooler" line are analog sensors used to drive dash gauges. They are not normally connected to the transmission control system, so do not show up on the J1939 databus.

[Ronnie Bledsoe 2006 Dutchstar 43']

I too have reached the 212 degree temp while using the Pac brake on long downhill grades. I do not believe that to be unusual and the temp resumes its normal operating temps once on flat ground which is in the 203-208 degree range. When the dash heater is on this temp drops about 12 degrees. I have the aqua hot ready hot water system which may attribute to the normal 203-208 degree range

[powerboatr]

man you guys have me confused as well.
when i use the exhaust brake, my temps have dropped to 140F from 200
and running down the road at 65 mph is usually 190-200F

[rmmpe]

powerboatr,

I use the Silverleaf VMSpc program and mine runs just about where yours does.