Transmission temp sensor placement

AusOrion · Nov 24, 2009

Hi there everyone,

I have an Autometer temp sensor gauge. I was thinking about doing a whole transmission pump and cooler setup from NSN but have scaled back that plan (along with a few others) in terms of modding the car. Now, I just want to somehow place the sensor so it will read the transmission fluid temps (without any pump / cooler setup).

So, my plan is to mod the actual sender (sensor) unit for the gauge into one of the transmission drain plugs so that it will be sitting in the transmission fluid and read the temperature. Attached below are two images - the first is a schematic of the gearbox and the locations of the drain plugs shown in red, and the second is an image of the sender (sensor) itself.

By orion_3582 at 2009-11-24

One of my concerns is whether the sensor will interfere with any of the internal parts of the transmission. Can anyone shed some light on whether there will be a chance of interference between the sender and the moving parts inside the transmission?

Cheers.

TurfBurn · Dec 3, 2009

you should be able to get it in the drain plug without an issue and not hit anything. easy way to check though is to simply measure the distance and poke up in to see if you hit a structure. from what I recall though there is a fair bit of clearance above the drain plug area.

AusOrion · Dec 4, 2009

Excellent! Thanks for the info Steve!

I have a transmission bung plug being drilled and tapped to fit the sensor this weekend. Then its just a question of which bung will provide the best readings - the one at the front of the gearbox towards the drivers-side wheel or the one at the bottom of the gearbox towards the block??

From the look of it the sensor will sit about 5mm to 7mm out from the end of the bung. I was thinking of just poking something that was the length of the sensor to see if anything was in the way - good to hear that I was on the right track!

mp3-79bronco · Dec 4, 2009

one on the bottom will be the only one touching the fluid.......

AusOrion · Dec 4, 2009

mp3-79bronco said:
one on the bottom will be the only one touching the fluid.......

Really, I have seen several posts about replacing the gear oil and all of them say that the fluid should be sitting just below the level of the fill plug. If this is the case, how is another plug sitting at about halfway between the top and bottom of the gearbox not going to be covered by gear oil?

mp3-79bronco · Dec 4, 2009

u just answered ur own question....the fluid sits just below the plug....

AusOrion · Dec 5, 2009

mp3-79bronco said:
u just answered ur own question....the fluid sits just below the plug....

Well, not really. My understanding is that there are three plugs - one fill plug at the top and two drain plugs (highlighted in the red in the picture above) which are at the front of the gearbox towards the drivers-side wheel and down the bottom of the gearbox towards the block. Is this correct?

mp3-79bronco · Dec 5, 2009

nope just two. the one on the side is the fill plug. and the bottom is the drain

AusOrion · Dec 6, 2009

mp3-79bronco said:
nope just two. the one on the side is the fill plug. and the bottom is the drain

A-ha! Everything making sense now!

It also makes the placement of the sensor very easy too as there is only one logical place to put it.

Now I just have to wait for the tapped drain plug to be sent back to me, then I just have to install the gauge into my triple gauge din holder, and finally hook everything up.

Will probably switch from Redline to Royal Purple when I drain the gearbox to install the sensor.

AusOrion · Dec 13, 2009

So I got the transmission drain plug back at the end of last week. I found that the first half of the die-cut thread in the middle was fine but after that it was really hard going to get the sensor in.

So we ended up using two wrenches to turn the plug and sensor in opposite directions. The problem with this is that because we had to put so much force into the turning the wrenches, we didnt feel the sensor bite down onto the top of the plug. The end result was that we sheared the sensor in half

I have another transmission plug waiting in the wings and Im going to get the thread cleaned up a little so that the sensor will be a bit easier to put in. I also just ordered a new sensor and should have that later in the week. Will try it again on the weekend.

mp3-79bronco · Dec 13, 2009

need to tap the thread deeper

AusOrion · Dec 13, 2009

mp3-79bronco said:
need to tap the thread deeper

Yup, going to have the thread tapped all the way through the bung. There is plenty of meat in the bung, so Im not at all worried about tapping the centre of it. I'll post up some photos in the next day or so if I get a chance.

Then going to use a fibrous washer between the bung and sensor to form a nice seal.

AusOrion · Dec 20, 2009

Engine mount problems aside, I did manage a bit of progress tonight. After one failed attempt to thread my transmission temp sensor into the bung, I gave it another go with the help of my bro. Look below:

The one on the right is the first (err, unsuccessful) attempt - the disc on top of the sensor head is a washer. We originally thought that the we would need to create a seal at the top, but it turns out that the thread is tapered (slightly smaller at the bottom) and will seal up on its own. What happened was that it was so hard to screw the sensor in that we did realise how close we were to the bottom of the thread. So when the head of the sensor hit the washer, we didnt feel it bite and as we turn a bit more we ended up shearing off the top of the sensor

The one on the left is the good one - I was keen for one more half turn, but my bro was a bit more gun-shy after the first try. We can always tighten it up a bit more if it does leak a bit (not likely). Just have to change the transmission fluid now so that I can swap the bungs out and then I just will have to connect the sensor and all done. Easy peasy. Got some Royal Purple sitting in the garage, so will give that a try this time around. Then just have to get my DIN triple gauge holder sorted

AusOrion · Jan 7, 2010

So on New Years Day, I finally got around to changing the gearbox oil. I jacked the car up and put pan under the transmission. I put the spanner on the drain plug and give a mighty heave, and the bolt loosens immediately. So as the old transmission fluid is draining I went to work on the fill plug - whole different story. We now suspect that the transmission shop used an air tool (i.e. rattle gun) to put it on as it was a b!tch to get off with the breaker bar. It came off eventually and we saw that it had been put on so tight that the washer had basically fused to the plug. See below:

Lucky I was installing a new plug with the sensor in it and could use the stock drain plug to replace the fill plug. The old gearbox oil had some metal filiings in it and Im hoping that a change or oil will help to prevent that and make shifting a bit smoother:

Hopefully the Royal Purple will prove to be a better gearbox oil and there wont be as much metal filings when it next gets changed. Finally, here is a pic of the sensor sticking out of the gearbox, just to one side of the main support bar that the front and rear engine mounts are attached to. Sorry about the pic quality as it was late when I took it.

Now I just have to monitor the sensor for a bit and make sure that no gear oil is slowly leaking out.

slavrenz · Jan 7, 2010

Maybe it's just me, but that looks awfully susceptible to being ripped out of your transmission by road debris catching on it.

Joost27 · Jan 7, 2010

wow yeah that sticks down there, I would find a better way to mount it.

AusOrion · Jan 7, 2010

slavrenz said:
Maybe it's just me, but that looks awfully susceptible to being ripped out of your transmission by road debris catching on it.

IukekiniProtege said:
wow yeah that sticks down there, I would find a better way to mount it.

It is quite close to the main beam just there which will provide protection.

Also, when I sheared the head off the first sensor the probe part of the sensor body staying in the plug (threads and all) and maintained a complete seal.

Unless you drill and tap the transmission housing (nailbyt), I dont seeanother way to place the sensor.

Something like NSN's trans cooler kit would need an adaptor pipe coming out of the same location. I would think that it would be a depth to the sensor I have.

slavrenz · Jan 7, 2010

AusOrion said:
It is quite close to the main beam just there which will provide protection.

Also, when I sheared the head off the first sensor the probe part of the sensor body staying in the plug (threads and all) and maintained a complete seal.

Unless you drill and tap the transmission housing (nailbyt), I dont seeanother way to place the sensor.

Something like NSN's trans cooler kit would need an adaptor pipe coming out of the same location. I would think that it would be a depth to the sensor I have.

If you're fine with it, all the more power to you. Personally, the cost to drill and tap a new hole for the sensor slightly higher up would be worth the piece of mind for me. I'd be out looking underneath my car anytime I went to drive it somewhere to make sure nothing got ripped off.

AusOrion · Jan 7, 2010

slavrenz said:
If you're fine with it, all the more power to you. Personally, the cost to drill and tap a new hole for the sensor slightly higher up would be worth the piece of mind for me. I'd be out looking underneath my car anytime I went to drive it somewhere to make sure nothing got ripped off.

I take your point.

If was something else and not the transmission, then I would have considered drilling and tapping a new bung in. To my knowledge, no-one has put an extra bung in a G-series transmission. These transmissions need as much care as possible at the best of times and drilling the case is not a path that I am keen to go down.

slavrenz · Jan 7, 2010

AusOrion said:
I take your point.

If was something else and not the transmission, then I would have considered drilling and tapping a new bung in. To my knowledge, no-one has put an extra bung in a G-series transmission. These transmissions need as much care as possible at the best of times and drilling the case is not a path that I am keen to go down.

I guess I don't have a lot of experience with these trannies (I have an automatic), so I can't say whether you'd have any issues. But I suppose if the sensor did get torn off, you'd probably see something going on with the temp gauge to clue you in before you did any major damage.

Transmission temp sensor placement

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