How much difference in temperature is there between an auto tranmission sensor placed in the pan vs in the hot line coming out of the tranny heading to the cooler?

I just put a sensor in the hot line on my D250 extended cab pickup. I am running close to the max GVRW with my camper on the truck. Driving highway speed (65) it is running about 195. It seems a bit high but I have nothing to compare to other than being told "220 max for a sensor in the pan".
I figure I can manage it by slowing down in the mountains but am wondering how much cooler the pan is than the fluid leaving the transmission.

Rocky

 

You have the best location now. Search DBF's posts. He has multiple sensors switched to one gauge for that excessive monitoring moment...

If you want to know how hot the transmission is actually getting for the purpose of preventing damaging heat, then you have the best location for detecting that heat. Trans. fluid in the pan has been thru the cooling circuit, not much sense in monitoring cooled fluid IMO.

You might want to consider an auxiliary cooler, just my opinion.

 

don't know what the difference in temps are but i too have mine in pan. i run about the same temps as you when pulling my camper. highest i seen on my trip this weekend was 195 going up some pretty big grades (for PA at least).

 

Not quite. I finally got around to cyphering that part of the hydraulic circuit (FSM and dealer service manual use the same hydraulic schematic).


That fluid in the pan has been through the transmission (clutches, servos, etc) and reflects the temperatures there.

That fluid coming out of the trans (and running past that sensor), is that from the pan that has been picked up, and run through the trans oil pump on its way to . . . . . .

In Park ~ the valvebody's pressure regulator valve, manual valve, and boost valve. Nothing more. No flow through the heater/cooler(s), etc.



In Neutral, and otherwise ~

(1) ~ the valvebody's pressure regulator valve, manual valve, and boost valve.

AND

(2) ~ From the pressure regulator valve to the torque converter and front clutch lube, then to the heater/cooler(s), then to lube the trans bearings.


Reference pages 21 - 121 ~ 122 of the FSM and 1993 dealer service manual no 81-370-3108 (typical of the 32RH, 36RH, 42RH, and 46RH).
NOTE: The Switch Valve of the valvebody is omitted as it relates to the lock-up trans and is not applicable here.



I wish there was a genuine schematic of the A518 specific was available . . . . .

 

The correct gauge placement is the front hot oil out line, The fluid in the pan is returning from the cooler circuit, the back oil line.

 

Go on over to DTT's site and ask where the gauge should be and why. Might as well ask what the difference in temps are since that was the original question here. Bill will set you straight...