Trans temp

With the trans temp sender in the pan what is the ideal trans temp and what is to hot?

150-180 I'd call ideal.

I have buried the trans temp gauge on mine twice (250) when hot lapping multiple classes with no ill effects. Tom Bogner @ Lucas Oil said their trans fluid is good to about 275 before he would start to worry.

I would agree in a bracket car somewhere from 160-180 would be a ghreat target. I too have buried mine hot lapping the car. Could feel it through the tunnel. Had a couple times I just taped over the gauge so I couldn't see it. Never had any ill affects from it.

The pan is the correct place to get that temp. Putting it in the line right off of the converter is like putting a water temp gauge sender beside an exhaust port in the head.

Temperature chart.

Well good thing my trans temp gauge only went to 250 then...

I have my sender unit in the return line from the cooler. 6k stall converter with a brake, the highest I've seen is 220*. So the trans itself would be cooler than that

If its the return from the cooler then your seeing the cool side not the hot side ?

The hottest fluid is the line from the converter to the cooler.
The cooler fluid is the return line.

Think turbo intercooler.

The trans sees the return line fluid temp - not the converter to cooler temp.
Very little fluid from the converter gets pumped directly in to the trans.

The red dye in most standard ATF, not synthetics starts to change color at 275 F, it will start to go from bright red to brown above 275 and go solid black at and above 325 F according tp literature I read years ago in a college auto shop class, it was on one of the test questions
My airplane oil cooler thermostat was set at 190 F before opening, it would run from 195 to 220 F once it was operating at or above 1500 RPM for 20 minutes or more regardless of outside air temps. or altitudes
If I could control both my oil temps and tranny temps. precisely I would be happy to see from 180 to 240 F
Hot oil moves easier and quicker than cold oil as well as the volume increases at the same time
I put my tranny temp sender in my old Ram 2500 CTD in the left front corner of the tranny pan, the guys on CTD web site said to mount it in the front servo on top in the 1/8 NPT pressure check boss, I saw no differences in temps between the two

I disagree. I want to know how hot the transmission is. So to me that means measuring the fluid after it flows brought the transmission. Once it’s in the pan it’s been through the cooler. Essentially, if you measure in the pan, you’re measuring how cool the fluid is at it’s coolest point, not how hot it is. . Think about where your engine coolant temp is measured..... do you measure it where it comes out of the radiator?

To the OP: Pat Blaise, one of the foremost torqueflite guys in the nation, once told me that 250 is the point where fluid starts to foam, so you want to shut it down if it gets up around there.

I Change mine every 20 runs, Or when it smells like sulfur. LoL. Turbo on the trans break is hard on stuff. I run CAT wet clutch hydraulic fluid in the converter drive and 30wt in the Lenco.

At Chrysler (FCA) we check the fluid temperature in the trans pan in production transmissions.
That’s because we want to know what the trans sees for fluid temperature.
Cooler line temperature on the converter side out will always be hotter than sump temperature and everyone knows that.

The focus of development of coolers for transmissions is on heat extraction and getting the efficiency to a point where the fluid temperature coming back to the trans is sufficent to protect the trans.

You can stick your sending unit where ever you like but the sump is the correct spot if you want to protect the trans.

BUT!!! .....in the 46/47 RH family the fluid temp sensor was IN the line coming off the converter pre heat exchanger. I actually used this line on my RE trans as it made a great place to add an aftermarket sending unit.

On my race car I have an aluminum log style heat exchanger, and then added another cooler via a new radiator with a stock style in tank cooler. In my pea brain I like to see where the fluid is hottest as it’s temperature that can break the fluid down. If I can manage the fluid at its hottest point, I know the sump is fine.

You are correct J Body.

Some trucks (diesel I believe) did have an additional sensor in the line - for one reason and one reason only.

They get driven hard for LONG periods of time and to protect the trans from sustained over temp they force the trans down in to 3rd gear and then force lock up so you slow down and cool the fluid IN the trans.

The chart included above is missing one explanation.

It’s called “time at temperature”.

Going to 300 degrees for 5 seconds then dropping to 200 a hundreds times will cause very little fluid degradation. What kills the fluid and the seals is keeping it at 300 for extended periods of time.

For those really worried about it my Friend makes and sells these.



http://jonestransmissionpumps.com/

Just one thing to think about is the fluid flow path. Almost everything we worry about with temps (bands, clutches, and seals) are all fed directly from the filter pickup in the pan. Obviously these are the components to be most worried about when temps get high. The last thing to be fed internally is the converter, which creates the most amount of heat. If you measure the trans cooler line out of the trans, you’re measuring a lot of heat created from the converter that will never directly get back to the clutches/bands/seals.

The converter by construction can take a lot more heat than the other internal components.

Measuring the hot side of the trans line will tell you the converter output temp, which might be important to you, but I would think that knowing the temp of what the more vulnerable parts are seeing is more valuable information.

That all being said, I would say I probably push these things as hard as anyone bracket racing a turbo car on a full tree. I end up being “on the converter” for a LONG time sometimes trying to get the turbo to spool, and chasing most people I race, which builds a LOT of heat. Aside from the first pass or two, my trans is NEVER UNDER 200 degree’s (pan measurement).

The ONLY time I’ve ever had an issue is a few years back when I was running a trans blanket. I think it was 2014’ish? At monster mopar in Norwalk I went to the last 3 cars in the 10’oh shootout, and the last 7 in pro. It was like NASCAR hot lapping the thing, and finally with the temps continuing at 300 degree’s pass after pass, the front pump seal finally gave up the ghost.

Since then, I switched to a carbon shield, and deeper pan. Now it usually runs around 250-275 degree’s on hot lap situations, and it’s never hurt a part. Is it ideal? Probably not. Do you guys need to keep your trans around 180 degrees? Probably not either.

Mine runs right around 150-180. 240 hot lapping. Just checked the frictions and band at 360 passes. Looked excellent. Still running the same seals, frictions, and band. Now at 400 passes.
Doug

I’ve gotten thousands of transmissions back with 150k miles or more out of gas and diesel trucks in the Reman program.

The most common failure mode was people not adjusting the front band.
The vast majority of transmission could have been bench repaired with a front clutch and band.

The seals and everything else were fine.

The architecture is fine as long as you perform some maintenance.

Then again there are people out there that can ruin an anvil in a sandbox with a rubber hammer.

Thanks for the replies guys. I run a plate style on my car and it usually stays in the 140-180 range, might get to 200 on a really hot day if I make it to the final. My wife car this past weekend pushed a little tranny fluid out for the 1st time was a hot humid weekend and she made it to the finals.). I have just a tube/fin style on her car and being a C4 (car is a 63 Falcon) it only holds about 1/2 the fluid of a 727. I ordered a plate sytle cooler that is the next size up from mine and going to put a gauge in it and see what temp it is running.

True. Oil returns to the trans from the cooler and is routed through the lube circuit in the rear of the trans, then falls to the sump along with oil being shed by internal components. Oil in the cooler lines has either been heated by the converter or cooled by the cooler. Oil in the sump has been returned from internal use and is being picked back up by the pump. Just like an engine with the sensor in the pan or dry sump tank, I want to know the temperature of that oil in the trans.

I'll stick with knowing what the actual oil temp is in the pan. Afterall that's where the fluid being circulated is coming from.

A guy I know, with a Chevy 454 TH400 dualie pickup, placed numerous temp senders in various parts of the system and hooked them to s single gauge through a rotary switch to monitor the temps while towing; wish I woulda written down the numbers cause now I have CRS.

you can check both locations, converter and sump with a single electric gauge and two pickups, using an on/off/on toggle switch to the sending units. best of both information wise.

My thinking is the tranny operates on the fluid that is sucked up from the filter correct?
Not from the converter
If you want to know the fluid temp coming out of the converter and then when it comes out of the cooler measure both

Most of the heat in a transmission is from the converter. Converter design, stall speed and slippage, sprag or not, etc. effects it. How you run the car, foot or transbrake, 2-step or not, etc.,is the biggest influence.

Why monitor trans temp? Just to try to avoid or detect damage? Change the dial according to how hot the oil is? Or to try to maintain a specific temperature for consistency?

The oil coming from the converter is what it is and usually spikes on the starting line when it's slipping the most. I don't know anyone who monitors just that. Bracket racers may monitor the trans temps with a sensor in the pan and adjust the dial or throttle stop accordingly. But some of the guys who bracket and .90 race seriously, monitor oil temps in the engine and the trans, and have heaters and coolers for both so they go into the water at the same temp - or as close as possible - from the first run of the day to the last.

Slightly O/T: is the ATF pick-up uncovered when the front wheels are airborn? It's certainly a concern for engine oil.

not if you are running a deep pan - a stock pan possibly

Since my deep pan didn't have provision for a temp sensor I monitor the line temp from the converter. At first I wasn't sure this was the best place for it. It sure goes up quick making a pass and the 8 in converter makes for more heat than the 9 1/2 in converter that I've tried in my current 580 combo. Obviously this is due to more slippage. I'm guessing if the converter started to go bad, temps would increase 60ft would drop off, trap rpm would increase etc. If one were to log such data it's just another tool in the arsenal for comparison and would help to identify any issues occuring in the entire package we call a race car