Tranny temp gauge sensor; where to put it?

   / Tranny temp gauge sensor; where to put it? #1  
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RobertN

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New Holland TC40D
I bought an Auto-Meter tranny temp gauge. I am not sure though, where to put the sensor?

I have an '01 Dodge Ram 2500 diesel 4x4 with an auto tranny.

Should it go in the pan, or in-line with either the in or out line for the cooler? I'm guessing there is not a port on the tranny case?

Also, has anyone added a secondary cooler to one of these trucks? I have the heavy duty tow/camper package already.
 
   / Tranny temp gauge sensor; where to put it? #3  
I mounted an aftermarket tranny cooler on one of my previous trucks. Bought it at Advanced Auto, mounted it in front of radiator, connected lower trans line from radiator to new cooler then ran new line from cooler back to transmission. My temp gauge was inline and additional cooler dropped temps while towing about 20-30 degrees. Your temps may vary depending on size of cooler you buy and placement.
 
   / Tranny temp gauge sensor; where to put it? #5  
   / Tranny temp gauge sensor; where to put it? #6  
I installed the Mopar line with the sender port in it (1/8" NPT) on my old 2001 Dodge diesel.

WH401 gives good advice, the sender in that location records the max temp of fluid, pan temps are often much lower.

The test port(s) are not designed to have anything screwed into them beyond a certain depth. I believe the test port on the pass. front corner of the trans will interfere with the movement of an internal cylinder. Don't remember the technical name of the part but do remember seeing pics of the temp sending unit in the path of moving parts inside the trans. Plus the temp at that location may not give you the max reading you would like to see.

If you get the new Mopar line, you should remove the fitting or the checkball on the inlet side of water to trans fluid cooler located on the pass. side of the engine compartment. The new Mopar line has a checkball installed (at least mine did back in 2001) where the line connects with the cooler. The checkball prevents trans fluid from draining back when the truck is not running. Two checkballs could prove troublesome.

I had a devil of a time removing the fitting from the inlet port of the cooler on the side of the motor. No easy way to get to it except from under the truck with an extension. I could feel the extension torquing/flexing and no movement from the fitting. Finally got it out but that sucker was in there and the truck only had about 14K miles on it at the time.

Some folks cut the line from the trans to the cooler inlet and install a compression T with a 1/8 NPT port on it. I wouldn't do it, the tranny line doesn't seem thick enough to support a compression fitting and it is a high vibration environment, the Cummins like to shake everything even remotely attached to it.

Not worth it to me, I spent the $80 on the new line and it worked fine, no worries about the integrity of the line while pulling 12K down the road.

Dave
 
   / Tranny temp gauge sensor; where to put it? #7  
I would not install the temperature probe into the cooler line. While the cooler line will report the highest temperature fluid it is not an accurate measurement of the temperature of oil supplying the critical components of the transmission - clutch packs, bands, seals, valves, solenoids, etc. It is at the end of the fluid path and can be readily heated up from torque converter slip.

I'd suggest to measure the temperature of fluid within the pan. A test port certainly is a convenient location to mount the probe but again is often in a location not accurate for measurement. The test port is designed to accept a pressure guage, not temperature. Using an adapter from the drain plug is an accurate location so long as it cannot be caught on the ground!

Otherwise I would suggest draining the fluid and having a bung installed on the pan (drill a hole and weld a nut to the side).
 
   / Tranny temp gauge sensor; where to put it? #8  
Josh61513 said:
I would not install the temperature probe into the cooler line. While the cooler line will report the highest temperature fluid it is not an accurate measurement of the temperature of oil supplying the critical components of the transmission - clutch packs, bands, seals, valves, solenoids, etc. It is at the end of the fluid path and can be readily heated up from torque converter slip.

I'd suggest to measure the temperature of fluid within the pan. A test port certainly is a convenient location to mount the probe but again is often in a location not accurate for measurement. The test port is designed to accept a pressure guage, not temperature. Using an adapter from the drain plug is an accurate location so long as it cannot be caught on the ground!

Otherwise I would suggest draining the fluid and having a bung installed on the pan (drill a hole and weld a nut to the side).
Click to expand...

Problem with putting the sender in the pan is that the fluid can take much longer to read accurately on the gauge, and by the time you do eventually see a high number, it's too late. Putting it in the cooler line is the best place because it gives you an almost instant reading to the fluid temperature. Torque converter slip is what will create the most amount of heat in an automatic transmission. As long as the TC is tight and efficient, or you are monitoring the fluid directly from it so as not to create an excessive amount of heat, than you'll be fine. And, if you keep the amount heat down from the TC, than you won't have any problems with the internals of the 47re.
 
   / Tranny temp gauge sensor; where to put it?
  • Thread Starter
#9  
The Autometer directions are vague "Oil and Tranny temp: Hole may need to be drilled and adapter nut(included) welded or brazed in pan."

So, my truck has the tranny cooler that is integrated with the motor.

If I add an additional/aftermarket cooler, I have to either break the line from the tranny to the motor and "T" in, or get a new line that is meant for this. I can "T" in the temp guage there.

If, I add a tranny cooler, where? The front of the truck is already packed with the radiator, intercooler, air conditioning.

I just had the tranny serviced, and a week later decided to get a temp guage. If I drop the pan, can I save the synthetic fluid? Do I have to drop the pan if I put the sensor in with the the new cooler hose and aftermarket cooler?
 
   / Tranny temp gauge sensor; where to put it? #10  
The Autometer directions are vague "Oil and Tranny temp: Hole may need to be drilled and adapter nut(included) welded or brazed in pan."

So, my truck has the tranny cooler that is integrated with the motor.

-> Tranny cooler is located on the passenger side of the engine, below the exahaust manifold. Is about 18" long, maybe 6" round. Follow the line out from the tranny, it runs to the cooler. It is a liquid to liquid cooler. Coolant from the engine also runs through the tank to help cool the AT fluid, much like the cooler built into the standard AT radiator.

If I add an additional/aftermarket cooler, I have to either break the line from the tranny to the motor and "T" in, or get a new line that is meant for this. I can "T" in the temp guage there.

-> I don't think you really need another cooler, buy the Mopar line or another line with the fitting for the sending unit already in place. The Mopar line is a nice piece, should be around $100, can probably find it for less. Compression tees are not the best idea for this application, lots of guys do it and never have a problem, I'm not that lucky. They way I look at it is you are adding two additional potential failure points with a T. I would install a one piece line with a fitting for the sending unit.

If, I add a tranny cooler, where? The front of the truck is already packed with the radiator, intercooler, air conditioning.

-> Not much room for an additional cooler, I would run the gauge for a while and see what your temps look like. If you temps are still high I believe DTT make a nice auxiliary cooler than fits inside/behind the front bumper. Not sure if they still just sell the cooler, you may have to buy the kit which includes the auxiliary cooler, line with port for sending unit, additional line, brackets etc.

I just had the tranny serviced, and a week later decided to get a temp guage. If I drop the pan, can I save the synthetic fluid? Do I have to drop the pan if I put the sensor in with the the new cooler hose and aftermarket cooler?

-> Don't have to drop the pan if you get the new hardline with the fitting for the sensor, see my earlier post. You remove the existing line and the fitting it connects to on the bottom of the cooler. There is a check ball in that fitting and I believe there is also one in the end of the new Mopar line, only need one. Some guys just remove the checkball from the fitting on the cooler using whatever means necessary, I would just remove the fitting.

When I did mine I lost less than a quart of fluid.

Here is some info from another web site discussing using the test ports for temp sender location.

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On the passenger side of the transmission there are 4 pressure ports and the driver side there is one port.

1st. or Front Port is the Front Servo Port; I have seen guys ruin their transmissions by putting a temp sensor in here. If your temp sensor probe is long enough it will actually make contact with the spring in the front servo, causing problems in 2nd gear apply cycle. This pressure port only has oil in it when you are in 3rd gear, & 4th gear. Since your tranny will build its max heat in 1st, 2nd, or reverse this pressure port is pretty much useless for accurate readings.

2nd or Middle port is your mainline pressure or what is referred to as your accumulator port, this pressure port has oil in it in 1st, 2nd, 3rd, & 4th but not in reverse. If you do not have an RV trailer chances are you are not going to overheat it when trying to back up your truck but if you do have a trailer again or want to monitor accurately it is a useless port.

3rd port is your low & reverse servo port. It is the one that faces towards the rear end. This pressure port has oil in it only during reverse & manual low applications. Making this pressure port pretty much useless to measure from as it has no oil in it during the 1st, 2nd, 3rd or 4th gear.

4th pressure port is the governor port. It is located about 4" above the 3rd pressure port. Basically this pressure port gets energized with vehicle speed. But it has no oil in it during reverse application.

# 5 pressure port is the 4th gear pressure port. It is located on the driver’s side of the transmission above the rear cooler line going into the transmission case.
It only has oil in it during overdrive apply. Hopefully after reading this you guys can see why we do not like customers using pressure ports to take readings from. A lot of customers use these ports because it is convenient; a lot of shops use these ports because it is a profitable & quick install.
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Good info, when I had my truck with the auto and tranny temp gauge I would usually see max temps while slowly backing heavy trailers uphill. It was surprising to see how high and how quickly the temp gauge would climb.

Good luck with whatever you decide.

Dave
 
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