transmission temp sensor placement

[aaronwilliams]

This is my first post so let me know if I'm posing/ formatting this question properly.
I have a 1988 Chevy V30 dually cab n chassis
454 4bbl
turbo 400 hd
NP 205
corporate 14 rear Dana 60 front

I do a lot of towing and hauling and I plow and sand with the truck as well. Ive had multiple people driving the truck over the past few years and its now on its third tranny. ( a couple long/painful stories short, the second one was due to insufficient cooling)

originally the tranny fluid was cooled using just the stock intercooler in the radiator. when I put this 3rd TH400 in last year I added an aftermarket air cooled heat exchanger mounted behind the grill. (got rid of the ac condenser along with the compressor and air pump and a bunch of other plumbing "extras".)

I recently bought a oil/water electrical temp gauge and have installed it nicely in place of the common "blank" in the bottom left instrument  bezel. I have it wired to turn on with the ignition and even got the light to dim with the rest of the panel.

I know they make tranny pan plug kits and I think the pan is the standard location for a fluid temp measurement but it would be much easier for me to install the sensor in the return line between the aftermarket cooler and the transmission. Is this an appropriate place to get a good reading? 

Any info or insight would be much appreciated - thanks

 

[frotosride]

As long as you check and double check that you put it in the supply  and not return side (leson learned) there wont be any problem with getting an accurate temp. I'd just reccomend plumbing the sensor in-line as close to the tranny as possible to get the most accurate reading.

[frotosride]

Another thought,....i'm not sure how the sending unit you have works but the only forseen problem in plumbing it in the cooling lines would be if the sensor requires the body as a ground path and you are using rubber hose to connect the cooler. it would take a little soider and a wire to fix if you still want to run it that way.

[roger97338]

B&M makes a tranny temp gauge kit. It comes with fittings to splice into one of the fluid lines, and install the sending unit there. I'm going to go out on a limb and guess that B&M has done that sort of thing more than once, so that location must be just fine.

Since I've never installed a transmission temperature gauge in any of my vehicles, I can't offer any personal experience to you.

Here's a link to the gauge I mentioned, if you want to take a look at it: http://www.summitracing.com/parts/BMM-80212/

[beastie_3]

It needs to go in the "hot" line. That will be the most accurate reading.

I used this http://www.summitracing.com/parts/ATM-2287/ for my transmission line because I already had a gauge.

[aaronwilliams]

Thanks for the input, The guage i have only goes up to 290 and i think I'll go with the hot output from converter line for the location. Ive got a feeling that will be the most informative. However out of curiosity and a desire for backing up information with data im really considering putting a second $20 temporary temp gauge in the return line for comparison.

I am curious about what my aftermarket cooler is doing to my return temp...

found this after i posted my question last night and thought others might appreciate.

Here is a quote from the Orange ($8.95) GM manual:
--------------------------------------------------------------------------------------

"OIL TEMPERATURE MEASURED AT CONVERTER OUTLET TO COOLER.

300F is the maximum temperature. (Workhorse says 350F). This is the normal place to install a temperature gauge or signal. The temperature in this location will vary significantly with each vehicle start-up or hill. If the temperature reaches 300F (350F), reduce throttle. To lower the transmission temperature with the transmission in NEUTRAL, run the engine at 1,200 RPM for 2-3 minutes to cool the oil. Do not allow the converter outlet temperature to exceed 300F (350F).
Keep a close check to prevent the engine cooling system from overheating.

300F would be typical of rocking the vehicle in mud, snow, or sand, or a transmission in stall (full throttle, no vehicle movement). When the transmission is in stall, the transmission will develop heat at a rate of one degree per second of stall.

OIL TEMPERATURES MEASURED IN THE SUMP

150F -- Minimum operating temperature for continuous operation. It is possible in low ambient temperature to overcool the transmission with oil to air-type coolers; it is hard to overcool if used in conjunction with oil to water coolers installed in most standard automotive radiators.

190F-200F -- Maximum oil level checking temperature. Beyond this, readings are not reliable because of expansion.

285F -- Maximum sump/oil pan temperatures for short duration such as a long hill climb.

300F -- Metal parts inside the transmission begin to warp and distort in varying degrees, seals melt rapidly, and transmission fluid life is extremely short due to oxidation and distress.

AUTOMATIC TRANSMISSION FLUID OXIDATION Automatic transmission fluid
can provide up to 100,000 miles of service before oxidation occurs under normal operating temperatures of about 170F. Above normal operating temperatures, the oxidation rate doubles (useful life of the fluid is cut in half) with each 20 degree increase in temperature. The approximate life expectancy at various temperatures is a follows:
Degrees F Miles
175 100,000
195 50,000
212 25,000
235 12,000
255 6,000
275 3,000
295 1,500
315 750
335 325
375 80
390 40
415 Less than 30 minutes

After-market temp gauge should be installed in the lower (hot) line entering the lower fitting of the radiator.

After-market external oil to air cooler should be installed in series. The hot oil line should go first through the aftermarket cooler then into the radiator to maintain proper minimum temp of the trans in low ambient temps.”

End of GM copy from orange manual.
------------------------------------------------------------------
Note: Later (green) manual says run through radiator heat exchanger first. Don't know why they changed.'

this info was quoted from http://www.ifsja.org/forums/vb/archive/index.php/t-134261.html

[aaronwilliams]

so to follow up on this ive done a little experiment I thought some might find interesting: I installed my primary guage on the output from the tranny to the radiator and a secondary $20 guage on the return line after my secondary cooler.

to clarify the fluid goes from torque converter, past guage 1, through radiator, through aftermarket air/fin cooler, past second guage and back into tranny.

So without load under normal driving 30-50mph flat roads tranny temp guage 1 is around 130-160deg with return guage bottomed out(100deg min). keep  in mind air temp in new england has been in the 30s and 40s during these tests so with cold air going past the second cooler the return temp could be quite low

flooring it up a hill with a trailer i get guage 1 up around 200 depending on duration but return line guage 2 remains very low around 100 -110 but it is reading.

At idle not moving guage 1 will rise to 180-200deg with the return reading between 110-130. if i put in drive, gas it and hold the brake to simulate a stall condition  i can dramatically raise guage 1 and slowly raise guage 2 readings.

I was plowing the yard ( less than 10mph) last night and it was around 30deg ambient. I had a tranny temp upwards of 250 deg with the return running around 180.

Cant wait to see the numbers during the summer, in the pic you see the two sending units. note the extra ground i thought i needed on the return line T. forgot i was putting the single wire on the hard line and the 2wire on the rubber.

[bake74]

      That is the correct way to document trans temp, both out going and incoming.  Just make sure to document outside temp. and diving condition also as you have been doing, it would make for some interesting data after a year of documenting if you put it in a spread sheet type read out for information purposes.
     I would be interested in seeing the results like I said after a year or so.