Auto tranny temps

crash2 · Dec 2, 2006

So---when you auto guys put a temp sensor in (cooler line style) what do you wanna know--The temp coming out of the trans or the temp coming into the trans after the cooler has tried to cool the fluid down? Since all the auto's I know the cooled fluid goes into the valve body/clutch packs so I would assume you would want to know what the temp coming into the trans would be..

thanks.

TreeClimber · Dec 2, 2006

Just buy two senders, and one guage. Put a toggle switch in line with the guage, and read both temps.

BTW, if it's an in-line sender, make sure it's grounded.

crash2 · Dec 2, 2006

TreeClimber said:
Just buy two senders, and one guage. Put a toggle switch in line with the guage, and read both temps.

BTW, if it's an in-line sender, make sure it's grounded.

Its one of those styles thats built into the guage/hardwired to it...

TreeClimber · Dec 2, 2006

crash said:
Its one of those styles thats built into the guage/hardwired to it...

bummer,

I've been told that the correct way to measure is BEFORE you've cooled the temp, that way if the tranny is overheating, you really know it and are not fooled into thinking that the tranny is fine just because you have a steady flow of cool fluid being poured back into the tranny.

The correct way to measure (or so I've been told) was to install the sender directly into a port of the transmission pan and measure the temp of the body of fluid.

T

no excuses · Dec 2, 2006

I've got my temp sender in the pan and it works for me.:kiss:

Roccrawler · Dec 2, 2006

leaving the tranny

Bunk1 · Dec 2, 2006

Roccrawler said:
leaving the tranny

Good to know..This should be in the " tech sticky "

archer1965 · Dec 2, 2006

Roccrawler said:
leaving the tranny

x2. that's what's in the trans.

Tankota · Dec 2, 2006

Ditto ditto ditto. Put the sending unit in the pan fluid. The OBS PSDs have a plug that you remove to put the sending unit in the pan fluid.

FYI, putting my truck in low range on those long steep gravel roads dropped my tranny temps to normal and my egts by half.

crash2 · Dec 3, 2006

Roccrawler said:
leaving the tranny

Thats how I would want it butr was not sure how it was being done. Since the crital temp is the incoming to the trans I would think you would wanna know when it was critical....

As for in the pan--I fully agree but this is on a TJ and there is no implement for that type of setup from what I have been able to find...

So for the second/important question---anybody know what line on a TJ is in/out on the cooler lines?

Digger 5 · Dec 3, 2006

I have gauges set up both ways. 1 Jeep has it in the line exiting the trans and the other Jeep has it in the pan. The Jeep with the gauge in the pan reads much more contant temps. You'll see the gauge rise but it's slow. With the Jeep with the gauge in the output line it's SCARY. That gauge moves fast. You can watch it climb as you power up a long grade. I've been tempted to do as Treeclimber said and add another gauge in the pan. Then I could see how efficient the cooler is operating.

Bunk1 · Dec 4, 2006

Digger 5 said:
I have gauges set up both ways. 1 Jeep has it in the line exiting the trans and the other Jeep has it in the pan. The Jeep with the gauge in the pan reads much more contant temps. You'll see the gauge rise but it's slow. With the Jeep with the gauge in the output line it's SCARY. That gauge moves fast. You can watch it climb as you power up a long grade. I've been tempted to do as Treeclimber said and add another gauge in the pan. Then I could see how efficient the cooler is operating.

HHHHHMMM, Maybee after cooler. But really i wanna see gages move so im thinkin outlet...It will look like im doing sick sh!t all the time

TreeClimber · Dec 4, 2006

crash said:
As for in the pan--I fully agree but this is on a TJ and there is no implement for that type of setup from what I have been able to find...

Pull the pan, drill a hole, weld in a bung, mount sender, reinstall pan.
While your at it, good time to do a tranny service.

Travis1 · Dec 4, 2006

crash said:
Thats how I would want it butr was not sure how it was being done. Since the crital temp is the incoming to the trans I would think you would wanna know when it was critical....

I would have thought the critical temp would be leaving the tranny, as close to it as possible.

Isn't it possible with a big enough tranny cooler to have fluid leaving the tranny at 250* but coming in at 170-180*?

Grama · Dec 4, 2006

My 2 cents. I have a built th350 in my buggy with a couple high dollar pieces in there. For this reason i researched where the best place to put the tranny temp gauge is to closly monitor my temp. IF you want to mount it in line, I was told it needs to be on the return line from the trans cooler. Tranny People ive talked to both hotrod and diesel advised me to put it into the pan or through one of the fuild ports on the tranny. If you buy the autometer tranny temp gauge you can mount the sender in one of the ports and it will not effect fuild flow in the tranny. There is one that is advised and if you want to know i can double check on mine for you.

wheelinjp · Dec 4, 2006

Well I installed mine inline with fittings on the 700r4 I used to run on the out to cooler line. It wasnt good for flow, so I found that the tranny had a bung in the side of it that fluid ran past but didnt effect flow. It read accurately there in the outgoing fluid(was told this). I now run a th400 and dont use the temp sensor.

skrause · Dec 4, 2006

Travis said:
I would have thought the critical temp would be leaving the tranny, as close to it as possible.

Isn't it possible with a big enough tranny cooler to have fluid leaving the tranny at 250* but coming in at 170-180*?

Exactly! You don't measure engine coolant temp at the return, why would you with an auto?

Roccrawler · Dec 4, 2006

crash said:
Thats how I would want it butr was not sure how it was being done. Since the crital temp is the incoming to the trans I would think you would wanna know when it was critical....

As for in the pan--I fully agree but this is on a TJ and there is no implement for that type of setup from what I have been able to find...

So for the second/important question---anybody know what line on a TJ is in/out on the cooler lines?

My first pick would be in the pan in the side port, but otherwise in needs to be from the tranny to the cooler, after the cooler is a false rep of what the tranny is running at.
As others have stated :;

Harvester of Sorrow · Dec 5, 2006

Roccrawler said:
My first pick would be in the pan in the side port, but otherwise in needs to be from the tranny to the cooler, after the cooler is a false rep of what the tranny is running at.
As others have stated :;

Actually Mike...

The guage needs to go POST cooler. As in the pan...or if there is not enough pan space, then as Graeme indicated, in the return line FROM the cooler...

The purpose of the guage is to read the temps of the fluid entering the tranny...which is an indicator of the cooling systems efficiencies and the "running" temperature of the tranny. If said cooling system becomes over worked and incapable of cooling the load on the fluid...it will be visible on the guage.

The fluid temperatures leaving the transmission will be well above 250-280 in a wheeling situation...but this fluid is only the worked fluid.

Anybody that doubts that should take a thermal IR heat gun on a run with them and take a minute to poke around their rig for temps...

After the cooler Mike.

PUO-BANNED · Dec 5, 2006

skrause said:
Exactly! You don't measure engine coolant temp at the return, why would you with an auto?

I agree that you should measure Engine temp at the source but an auto tranny has no thermostat to regulate the overall temp. It relies on the fluids ability to carry the heat away from the transmission to the cooler.

If I had only one guage it would be in the pan near the fluid pickup if possible
This would give the best overall reading of the system as a whole.