Engine/Transmission (1998.5 - 2002) Trans Temp qauage, what temp range

[JCyrbok]

Thinking about putting in a trans temp gauage and I'm looking that the Isspro line. They have two temp ranges, 140-320 and 100-280, which do I want or which is better? Its for the truck in my sig line.



Thanks

J-

 

[Yo Hoot]

I think I would get the 140-320. Who cares about what the temp is under 140. 260 is way too high so you don't need to read over that.

 

[cerberusiam]

Use the 140-320 if you like the range pattern, the other if the range looks better. Depending on what you do you cna easily push the temp in the TC over 300, you WANT to know its at that temp.

 

[JCyrbok]

copy thanks guys, i'm gonna go with the 140-320 one then



J-

 

[Yo Hoot]

Sorry I meant 140-320

cerberusiam,

So what's the story on the high temps built up in the TC. Many are now saying these are normal temps. The Dodge manual states anything over 240 on the trans gauge should be addressed with modified driving until it cools. . I wonder if the Dodge gauge sender is in the cooler pan area. If it is the TC temps might be 20 deg more.

That means if your stock trans gauge is reading 240 you could be spiking the fuid to 260 or higher.

It looks like we are constantly on the upper threashold of degrading the fluid. I get 220 normal driving around town consistantly coming out of the convertor (trans cooler line reading) dropping to 180 or less in lockup. Long hills and minimum lockup generates 240-260

Looks like it would be a good idea to replace the fluid 25-30,000 intervals.

 

[cerberusiam]

Sorry I meant 140-320



cerberusiam,



So what's the story on the high temps built up in the TC. Many are now saying these are normal temps. The Dodge manual states anything over 240 on the trans gauge should be addressed with modified driving until it cools. . I wonder if the Dodge gauge sender is in the cooler pan area. If it is the TC temps might be 20 deg more.



That means if your stock trans gauge is reading 240 you could be spiking the fuid to 260 or higher.



It looks like we are constantly on the upper threashold of degrading the fluid. I get 220 normal driving around town consistantly coming out of the convertor (trans cooler line reading) dropping to 180 or less in lockup. Long hills and minimum lockup generates 240-260



Looks like it would be a good idea to replace the fluid 25-30,000 intervals.

A lot depends on where you measure temp when discussing threshold temp. The OE temp sensor is in the pan, part of the gov pressure transucer on 2000 and newer trucks, when it is reading 240 degees it is HOT and in the danger zone.



Most of the heat generated in automatic comes from fluid shear in the TC, the looser the TC the more heat is generated because it is fluid coupling longer to get up to speed for lockup. In fluid coupling only a max of 50 psi is routed to the cooler so a lot of the fluid is being dumped right back into the pan after being heated by the TC, in lockup you have line pressure routed to the cooler so the bulk of the flow is being cooled and then returned, not to the pan, but as cooling and lube for the drive train part of the trans.



Trying to come up with a hard number that says you have overtemped things is tough. The fluid goes out of the TC at say 260 degrees on a hard pull, then thru the heat exchanger which will bring that close to coolant temp to around 200 degrees, then thru the front cooler which should drop about 40 degrees. That gives us return at the cooler at 160 to run thru and lube the trans and cool off the thrust washers. That could easily add another 50 degrees back to pan temp. We could now have pan temp around 210 degrees and everything is fine. Thats within parameters for the trans and the fluid. IIRC, in the Dodge\Cummins Talk it was stated 140-260 degrees is normal operating range. Check that as I am not positive on the top number.



Keeping that in mind, if you see 240 degrees in the pan the temp out of the trans could very well be 300 degrees or higher. Its not a perfect calculation becuase other factors influence the cooling. By the time you get to 240 in the pan the TC has been dumping a lot of heat into the fluid, I opt to watch the cooler output temp and when it goes over 260 degrees change driving habits.



Yes, if you are pushing the trans hard then a fluid exchange every 25-30k is a good idea becuase the volatiles eventually get cooked out of the fluid.

 

[Yo Hoot]

I guess my concern is the local temp spike that occurs coming out of the tc. 280-300 degrees is real hard on the fluid. When a fluid is rated a say 240, won't constant 280-300 deg spikes destroy the fluid in short order?

 

[cerberusiam]

ATF+4 is rated at 320 degrees for 1500 hours to meet ISO test standards for fluid shear, lubricity, etc. The operating range of the trans is different and what is referenced when talkng about say 240 degrees. The seals and frictions suffer when the temps go out of the operating range too long inside the trans. The temp spikes in the TC don't normally get to the internals becuase the hot fluid is dumped back to the pan to mix with cooler stuff and the rest is routed thru the cooler.



Really, if you see temps in the cooler output line going over 260 its time to gear it down and lock the TC. It would be an extreme case if they went over that and one has to make changes to limit the temp rise.



That is the nice thing about the gauge in the cooler line, you can react a lot quicker to extreme conditions and do something about it.

 

[JCyrbok]

thanks for the additional info guys. I would like to put the sender in one of the cooler lines with a tee fitting. SHould it be in the input to the cooler or the outlet of the cooler? Also when looking at the cooler from the front, which is the input and which is outlet?



Thanks



J-

 

[cerberusiam]

Sender goes in the output cooler line. Thats the front line on the driver's side of the transmission. It will have a rubber section that is a vibration damper and makes and excellent place to intall a fitting to put the sender in. Genos has the fitting that will make the job easier.



Otherwise, you can get the whole line form Mass Diesel and maybe others with the fitting already in the line. If you do opt to install a seperate fitting be careful tightening the fitting on the lines as they crush easily then leak.