bebbetufs

This is an alternative to installing a sensor in the drain plug for those who prefer a pemanent installation. It uses a VDO 1/8NPT (VDO 323.057) temperature sensor in the transmission casing. It is nice to know if the temp is in check when running at the track. This sensor will also tell you if you have lost the transmission fluid as it will no longer show the correct temperature.

I did this with the transmission on the bench, but it can be done with the transmission in the car. If done with the transmission in the care the casing must be properly flushed before the sensor is installed and new transmission fluid is added. The safest, cleanest way is to do this on the work bench when doing other maintenance.

NB! Proceed at your own risk, and make sure not to tap too far as you will not get a good seal that way.

1. The placement of the sensor in the bottom of the differential casing sump.


2. The hole is drilled at the bottom of the case at shallow angle pointing forwards. This is to avoid it protruding from under the case making it vulnerable to impacts.


3. There is plenty of material for tapping.The correct metric drill bit for 1/8 NPT is 8.6mm. The aluminium is soft so my 8.5mm bit worked fine


4. This is how the sensor should sit in the casing. It will protrude further when properly torqued.


5. Some material needs to be ground away to make room for the hexagonal head of the sensor and allow it to sit deeper in the casing. This also helps shield it from impacts. Back the 1/8 NPT tap out frequently and check the fit to make sure the threads start to become snug when there is still 1-2mm left before the head of the sensor makes contact with the casing. A Dremel with a ball-tipped carbide burr works well for this


6. The final result. The sensor sits deep enough to be out of harm's way, but I will add a shield to the bottom of the transmission casing anyways to further protect it. I will add to this post when the shield is done.

KevinGross

I've seen it done this way. My preference is to install a smaller temp sensor in the drain (bottom) plug. No chance of messing up an expensive case, easily reversed process (replace plug).

Kevin
Catellus Engineering

Tom M'Guinn

bebbetufs, thanks for the post and pictures! What are you using to read it?

bebbetufs

If you mean browser I use firefox!

Regarding using the plug vs drilling the case i guess it is a preference thing. Personally I do not like the sensor-in-plug installs, although I run that in the oil pan. To my mind they look like afterthoughts, and they tend to get in the way and get messy when servicing the car. My transmission was leaking and had to be taken apart to be sealed to hold the synthetic fluid I will run. I took the oportunity to do what I consider a clean install, and perhaps others may find it usefull somehow.

This can be done without dropping the transaxle for those who prefer a more permanent installation.

f1rocks

I think he's asking what gauge to read the temperature.....

bonus12

This is a unique thing for a 944. The job looks well done, and the car now has the equivalent of a factory-installed temperature sensor in the transmission. Cool project! Thanks for showing in any case.

StoogeMoe

Does anybody know what the normal tranny temperature is for an NA without a cooler at the track? I never pointed my infrared at it because I'm too busy with tire pressures and stuff.

Tom M'Guinn

Sorry, I meant to ask what you were wiring the sensor to -- a stand-along gauge, spare zeitronix input, etc.? And I agree re the drain plug approach -- cheap and easy, but not quite the same...

bebbetufs

I've been working on an arduino based digital gauge for quite some time now. Progress is slow at the moment as this is a winter project but every time I do maintenance on the car I add sensors when needed. The gauge/logger will read all the car's sensors and display the information on a single LCD panel. I am able to switch between primary, secondary and so on, views to display related information at once. It will also have customizable audible alarms to warn when things go out of whack. I'm planning to integrate it with the M-tune as well. Further down the line it will be a data logger. User input is via extra buttons in the button wells in front of the gear shift as well as a rotary encoder.

Until this is completed I will display the information on the same analogue gauge as the one reading the engine oil temp. I will just wire in an alternating switch to select either transmission or engine temps. I use the same sensor for the engine. I have not bought this yet as my car is stripped down to the torque tube at the moment.