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NAG 1 Dipstick and Temperature Measuring - DIY

66K views 44 replies 26 participants last post by  gfr-300SRT8 
#1 · (Edited)
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. In fact with my method you can leave the vehicle in PARK during the entire measuring process.

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 dipstick 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).
 
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#9 · (Edited)
Thanks for the compliment folks;

Another has asked about the relationship between the service tool sold by Miller and my graduated measurements added to the donor dipstick, so I'll elaborate further;

Both the Miller shop tool (PN9337 I believe) and my method measure fluid level from the bottom of the dipstick, in other words the fluid level is measured from the bottom of the transmission's oil pan. Both the tool I made and the Miller version have graduations every 10mm starting at the end of the tool, such that they must bottom out on the inside of the pan to achieve an accurate measurement.

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.

EDIT: some folks came up with using a long white zip tie...great idea and the darker fluid will shoe up that much better.



I hope you meant marks every 10mm and not cm
 
#4 ·
I did, and thanks for pointing out I needed an "m" and not a "c"
 
#8 · (Edited)
very nice write right up. I'll be putting this in my favorites. where did you get that thermocouple from? wonder if northern tool has one.
 
#10 ·
J-type thermocouples are as common as 3-gig megapots...joking of course :^)

Actually, any electronics supply, maybe even Radio Crap/The Source (what they are called here in Canada) will carry the actual thermocouple. If this is so, then it is likely they sell the module as well.

If you live in anything larger than a small town, the yellow pages will point the way to a dedicated electronics vendor.

There are lots of places online, not the least of which is Digikey (or Mouser, FAI, Future, Active, Electrosonic are but a few). Copy/paste the PN's I refered to and google them. At which point you will be inudated with many vendors and various price-points...

very nice write right up. I'll be putting this in my favorites. where did you get that thermocouple from? wonder if northern tool has one.
 
#13 ·
..not yet.
 
#15 ·
Will this method be close?

Fluid level should be measured with transmission in D or R (I believe?)

Drive around level parking lot a few min. when tranny is cold.
Stop on level, remove tranny tube cap.

Use any dipstick type device, as mentioned above, with a mark at 65MM and 70MM from bottom.
Block tire and parking brake on.

Idle in gear, with hand on upper and lower trans cooler lines.

As soon as the transmission cooler bypass closed, hot fluid will be sent to the upper trans cooler line. The tranny fluid has been recirculating and bypassing the cooler up to this point.
Immediately stab your device in the tube to bottom, remove and look at level.
Should be between 65 and 70 MM mark.
Should be well within serviceable range.

Best performed under a shade tree.

Pulling off the freeway, after a easy 65 MPH run, I've shot the pan and cooler inlet with a heat gum. temps are consistently at 168-170F at the Trans cooler inlet line.
My assumption is the cooler bypass closes at about 165, routing fluid through the cooler.
 
#18 ·
I'd go with the 12 guage wire first, before I stuck anything I spray painted into my transmission.

But that's just me.

Mike
 
#19 ·
Not having a temp gage, would a cold measurement be of any value? Say the car has sat 2 days in a garage at 90F, from the chart I would expect to see a measure of 35MM, correct? Does this do me any good, or is a hot measurement only accurate?
 
#22 ·
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.
 
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#23 ·
...actually, make it $200 instead of $250...
 
#24 ·
Great write up!!!!!!!!!!!!!!!
 
#25 ·
...actually, make it $200 instead of $250..
Not a bad price. I just paid 120 on the bay for 87 III with clamp. But I still need a Thermocouple Module. Infra red thermo will have to do for now.

I have looked hi & low for one of my cpl fish tapes, like we use for pulling wire in conduit etc. and can't find one. Grrr
I figure 40" of that would make a nice dip stick after marking appropriately.

Thanks for write up, good job.
BillyD..
 
#26 ·
awsome write up looks like its off to the store tomorrow
 
#27 ·
Thanks, I still have an extra DVM if anyone is interested...
 
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#29 ·
Nope, do you have the DCX service manual (pdf)? If not let me know. From that you can read up on the ATF fluid level test...
 
#30 ·
fnky? Park? Did the procedure change? The PDF I have says in Drive, wheels chocked, parking brake on. What page you on?

About the paint, I would never stick anything painted into the trans. Heck, Id even keep an eye on the insulation of the wire after every use for deterioration. I use a normal dodge dipstick, I straightened it in a vise, which made it too long, trimmed down to just hit the bottom of the pan, then marked my 10mm increments with small marks at the 5mm halfway points. I use my Dashhawk for the temp.
 
#31 · (Edited)
Setting transmission in D or R will accellerate ATF temperature increase (to within temperature-measuring range) and allow OBDII port reading to actually show ATF temperature (reads coolant temp only in PARK). Vehicle must be placed in "PARK" for actual fluid level measurement.
 
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