C6 tranny gauge

[tekrsq]

Hi there,

I know this is a little outside of this forum's "technical area", but I'm hoping some of you more experinced techies can help me. I have an 87 E350 (motorhome) with a carb'd 460 and C6 . It's a 3 spd with no overdrive. I'm trying to install an electric tranny temp gauge, but can't find the test port to install the sensor in. Does anyone know where it is ?

Thanks

[PhantomoftheBumpside]

At the hardware store?

Drill the pan near the front and install a fitting for the sensor. Use good some nice gaskets too.. don't go mucking up your trans vb by using sealers or rtv.

[tekrsq]

If I HAVE to drill the pan I will, but I was hoping there was a test port. I know it's an old tranny, but it still should have a test port shouldn't it ?

BTW: If I drill the pan, I sure as heck won't be using gaskets or sealant. The only way the bung should be mounted in the pan is to be welded.

[Donnie]

The test port that you are looking for is on the right front of the case , if you are comfortable using that to install your sensor, the thread is 1/8 pipe...If you want to see the most heat generated, that would be the front cooler line as 90% of your heat is generated in the converter. On hi perf builds , we always watched the temp in 3 places...The line to the cooler, the line from the cooler ( to see how well our cooler was performing) & the pan for a general idea.....You can wire 3 sensors to 1 gauge using a multiple position switch, or separate switches...
I am not a big fan of using the test port, although a lot of others do.....Donnie

[72BahamaBlue]

There are aftermarket stock type C6 pans with a drain plug built in. Can that be used with a sending unit?

[Donnie]

Don't think so, different thread.........Donnie

[tekrsq]

Thanks for the info, Donnie !!!!

Is there a certain type of fitting that I need to put the sensor in the cooler line? I would think there would need to be some type of "T" fitting that goes inline, or is there a better way?

[Donnie]

You are correct, a T fitting would go in the line if you are going to read your cooler . Other wise, for a general idea, just take your sensor to the hardware store and get a fitting to fit & braze or tig it into the pan....NOTE: some gauge mfgs. supply a pan mount kit with their gauge HTH.
.....................Donnie

[tekrsq]

Well, for what it's worth, a Ford tranny engineer (on another forum) said a test port was the best place to get an "average" temp, and the pan was the 2nd best because supposedly temps vary in the pan depending on location. He did agree the output line would show the hottest temps, but supposedly the fluid coming from the converter is the only fluid that will be that hot, and I should be looking the "average temp". Im not in a position to argue with him, so who knows.

Regardless, I've used test ports on various trannies before and had decent results. Anyway, I was finally able to get mine in the air a little bit so I could get a GOOD look at the tranny today. I have a test port !!!!!! HOORAY !!!!!!!!!

It is on the passenger side, just above the pan, near the rear of the pan. I pulled the plug out, and got fluid leaking. So I screwed in the temp sensor, and let it eat. I wasn't able to take the rig out to see what kind of temp I get, but idling it only went up to about 105-110F (I'm running a 180 F thermostat). Granted, ambient temps aren't that hot yet, and I didn't have the trailer hooked up, but I'm happy none the less. Atleast the gauge is hooked up !!!!!

[Donnie]

I'll take exception with your Ford"Tranny Engineer" from another site.....Test ports are just that... TEST PORTS, there is no fluid FLOW involved in these ports, they are DEAD end test ports meant to measure pressure only and will give you an average reading of the case temp & the fluid that is trapped in that area,, You will get a lower reading than you want if you are serious about tranny life... The life of your trans is related to the temp of the fluid in the holding units: that is, bands & clutches....Different fluids break down at diff. temps & when the fluid overheats past it designated point it loses it's ability to lubricate bearings, bushings & MOST IMPORTANT___THE VALVE BODY ! This is the beginning of your trans failure.....I know it is easier to screw a 1/8 pipe sensor into a test port, same threads.......EASY,, But I think you are more interested in your trans fluid life????? NO ????...........What you are reading at the test port is actually the case temp + or - a few degrees....Donnie

[basketcase0302]

Donnie,
I always wanted to monitor this on my slushboxes too. Thought about doing this so that in the coldest part of winter I'd have a bypass with a solenoid to take the cooler out of the equation.
Would installing a "T" at one of the cooler lines be a good place to read the temp then?

[Donnie]

Good Question....Basket, I'm not sure where to start...Lets Go---Organic fluids or mineral vs Synthetics.....The older fluids used to start to vaporize at around 220 to 240 degrees F At 260 some of the older seal compounds would harden and failure was coming...Some things have changed E.G.....the seals inside the trans are now made of a diff material, some of these I spoke of earlier,Buna, Nitrile, Silicone, Viton, etc..
They all have diff. properties..Some will wear better, some will tolerate heat better & so on.The older C6's used Buna in the foreward drum inner seal which was very close to the input shaft which would transfer a lot of heat from the converter & the seal would get hard & not seal, thus a slow foreward apply, or if forced to move before apply occured, the foreward clutches would fry ....We used to use a viton seal from a GM trans which would take the heat......A few years ago the kit mfgs. caught this & all kits now have upgraded their O rings.
The rest of your question was about bypassing the cooler in cold weather & temp reading.
Since 90% of trans heat is generated in the converter (fluid shear) the higher the stall of the converter, the more heat is generated.. If you are concerned about your fluid temp (Very impt.) the best place to monitor this is the line going to the cooler. C4 & C6 the front line is the line to the cooler. This is where you will find the most heat.
Something else that you may want to check out is a TRU COOL brand name cooler.. These are passive by dezine...When the fluid is cold & thick , it passes over the top of the down tubes in the cooler & returns to the trans. As the fluid warms up it will dribble down thru the tubes a & get cooled by the air flow..Sort of like a radiator..The Tube & fin design does not allow this. A lot of newer vehicles use the Tru Cool design. Using this type of cooler would eliminate your need to use a solenoid unless you were in a very cold climate.........Donnie

[Donnie]

Basket, I just reread my ramble, I'm not sure that I answered your question...BIG LAUGH
If you are just going to loop your cooler lines, you could probably just read the pan temp, but I would still use 2 sensors, so you could watch the converter output.........

[basketcase0302]

So would a "T" at both cooler lines be a good place to take that reading or elsewhere?

[tjm73]

I can't speak for anyone else, but I am only concerned about the hottest temperatures. If I know the hottest temps, I know the rest are lower and thus ok. I'd put the temp sender in the out to the trans cooler line. If you don't have a trans cooler, you should (especially in a heavy motor home).

When it comes to fluid temps, I'm not interested in average.