How To: NAG 1 Dipstick and Temperature Measuring

[Hemissary]

Since the procedure for checking the automatic transmission fluid in NAG-1’s requires correlating to temperature, I thought of a way for folks to accomplish this without the need of your local service department. The cost of an application-specific dipstick from industrial suppliers like Miller is in my opinion, ridiculous.
For a few bucks more one can not only develop their own way of accurately measuring NAG1 fluid levels, but also measure temperatures of other stuff. Add to this some of you will already possess a digital volt meter (DVM), which will further reduce cash outlay.

First I went to a local wrecker’s and chose a nifty transmission dipstick out of a Ford minivan. The minimum length required is ~40”, so FWD vehicles are convenient as generally their length is longer. The one I chose has a locking feature (expanding rubber plug), but after a little more thought I elected to leave the dipstick longer and actually attach the thermocouple to the dipstick shaft itself.



I cut down the donor disptick to a suitable length, then using a Dremel scored a line every 10mm (up to 10cm) along the bottom:



The Type J thermocouple used to measure automatic transmission fluid (ATF) temperature is very common. To read more, go here: http://en.wikipedia.org/wiki/Thermocouple This particular unit is from Fluke, actually it came with the thermocouple module. The PN for just the thermocouple is 80PK-1.



One either requires a DVM “with” thermocouple capabilities (a separate receptacle to plug in the unique spade-type connector), or a DVM that measures millivolts (mV) or volts (V) and a thermocouple module (Fluke 80TK is what I have – with this unit I can employ different types of thermocouples to read temps in excess of 4000F).

Using a long length if heatshrink, I sandwiched the thermocouple lead to the dipstick itself. When I insert the dipstick, I get the ATF level and the temperature in one operation. This is not a requirement, in fact you could insert the thermocouple lead into the transmission’s dipstick tube until it bottoms out on the oil pan, observe the temperature, then insert the dipstick and note the fluid depth (in cm) and compare to the graph in the service manual.



I have included a representation of the graph to save folks hunting the service manual or TSB’s:



One bit of advice; add a small amount of ATF (say 1/3 of a litre), then wait 5min while the dipstick tube drains sufficiently to prevent erroneous readings as the dipstick picks up remnants off the inside of the dipstick tube during insertion/removal. Being out a couple of mm either side for a given temperature is not critical, as the descrepencies of the measuring equipment exceed this tolerance. I also confirmed that the onboard thermocouple sensor employed by the PCM measured within 2C of the J-type thermocouple (I have the Aeroforce dual gauge set which shows amongst other parameters transmission temperature, TCC lock up, slip, etc through the OBD II port – the same sensor is used by StarSCAN/MOBILE).

NOTE: Those of you who use devices like Aeroforce or DashHawk which display transmission temperature by way of the OBDII port; When the vehicle is in "PARK", the OBDII port output for transmission temperature is not correct, and is actually displaying coolant temperature! Therefore, to observe transmission temperature, engage emergency brake and shift into "DRIVE" or "REVERSE" prior to adding fluid!

[kingswingin]

Damn... now THAT'S a write-up. Thanks for the info Moebius!!

[SoCalRT]

Very nice and useful write up...

[JRob007]

Very good info! Nice write up!!! BEANS a comin'!

[Hemissary]

Thanks, forgot to mention those of you who already use the Aeroforce gauge/dual gauge system or the DashHawk will see transmission temperature, you just need a dipstick.

By the way...you don't REALLY need an actual dipstick either. A length of 16-18awg household wiring (use the lead with the white PVC insulation - trannie fluid shows well on white) will also serve adequate duty as a measuring device.

[Dejacks]

Very good info Moebius! Thank you for sharing this...your a true DIY'er!

[05 MAG RT]

http://www.custommagnums.com/forums/...-dipstick.html

[Hemissary]

I agreed to put together a kit of the above parts for someone, they have since backed out.

So, if someone wants a nice FLUKE 333 Digital Clamp Meter, a Fluke 80TK Thermocouple Module, a Type-J thermocouple, I will let the entire shooting match go for $250.00.

Along with the ability to measure transmission fluid temperature (actually ANY temperature in/on anything) you will have a great DVM for any other AC/DC voltage/resistance/current measurements your little heart desires.

[Hemissary]

...actually, make it $200 instead of $250...

[riperoo]

Nice write up, really well done!!! Beans to you my friend

[TheFOSS]

Good info.. thanks for the write up!@

[Hemissary]

Why thank you...thank you to everybody who has commented...

[firetech]

Excellent write up on the trans level procedure. If you don't mind I'll add one more twist to make it even a little easier. We use an infrared Temperature gun to measure the temperature of the brake drums or rotors on our firetrucks. You can simply point the laser dot at the transmission pan and the reading you get will be within a dergree or so of the trans oil temp. As you had pointed out earlier, it's not an exact science and we aren't measuring the level with a dial gauge here!!! If the car is not perfectly level it would have a far greater effect on the reading than being a degree or two out on the trans temp. These guns can be found anywhere, even on e-bay for about $30-$50, then you can check all sorts of stuff, check your brake rotor temps, if one is cooler than the rest you know that is the one that isn't pulling it's weight and causing your brake pull, check coolant temp in and out of the rad, make sure the temp coming out of you catalytic converter is actually hotter than going in, check oil temps, tire temps etc and on and on. You can even point it at your forehead and do a check up on yourself!!! The main thing is the convenience, you can check temps on all these things without ever opening a cap or even getting dirty. Hope this adds to your already great write up.

[Hemissary]

Thanks firetech;

One word of caution though when utilizing infrared measuring equipment is that the emissivity of the surface you are aiming at will significantly change the measurement for a given temperature.

[Hemissary]

Updated first post with an addendum which reads:

NOTE: Those of you who use devices like Aeroforce or DashHawk which display transmission temperature by way of the OBDII port; When the vehicle is in "PARK", the OBDII port output for transmission temperature is not correct, and is actually displaying coolant temperature! Therefore, to observe transmission temperature, engage emergency brake and shift into "DRIVE" or "REVERSE" prior to adding fluid!