I have a question on trans temp steady state.. I just got my 79 RC pretty much done last night. I drove it for a few hundred miles prior to tearing it apart for paint/body 2 years ago. I had the trans rebuilt professionally before then, and didn't see anything abnormal afterwards. Now after putting it back together, I'm running down the freeway at 70 on my way to PowerTour, and the trans temp is about 200F. I have an external cooler, as well as the radiator one.

Is that temp normal? In my dads GTX with an external cooler, we rarely saw 180, and only when we were working it pretty hard. Truck has 35s with 3.55 gears if that matters. 360 with mild cam and aluminum heads, stock replacement converter done when the trans was.

What do you think? We thrashed the last two months to get this thing done for this trip, so if you have any ideas on things to check let me know. We are on our way from Detroit to Madison WI right now, and hoping it doesn't climb any higher. Thanks!

-Dave

It'll be whatever your coolant temp is, plus a bit. I ran coolers without the radiator, as the air temps will always be less than the coolant temps.

Where is the sensor located?

On my 2002 cummins I ran a deep pan 2 quarts extra with the sensor in the pan. On the road pulling about 9,000 pounds I was at 140 to 150. Without the load 110 to 120. 200 degrees is on the very high side of what I would like to see. If your sensor is on the output line it will read a lot warmer.

Sensor is in the line feeding the cooler from the trans. Thanks for the thoughts here. I'm going to disconnect the radiator cooler this evening and just run the external to see if that helps. Talking in the car, the other 727 car we have only has an external, so that will be apple's to apple's.

-Dave

You're reading the fluid temp straight from the converter, that'll be the highest temp reading, not the average temp and probably won't change much with a cooler change.

If the trans is a non-lockup, you are going to see higher temps with that gear and 35" tires especially in the square nose old trucks. They are like pushing a barn door into the wind.

Where should the temp sensor be installed? Right in the pan?

Hotly debated topic... but I think a bung in the pan is best and most common. Also, this location is the reference for most operating temp guidelines. The line to the cooler is the right after the torque converter... hottest point in the system. Pan temp will be lower and better reference.

You can also run one gauge with two probes [line and pan] and with a switch toggle between them.

My deep aluminum pan was easy for me it had a tapped bung ready for a probe when I bought it. Also a deep aluminum pan will cool and with the added fluid keep it cooler yet.

Well after the feedback here and talking to the guy that built my trans, I moved the sensor to the line leading back to the trans (post both radiator and external cooler). That reading seems pretty steady and acceptable, within about 10 degrees of the engine temp. I ran just the external for a morning, and didn't like the temps I saw sitting in traffic with minimal airflow. Hooked both coolers back up, and it seems much better.

Thanks for the feedback!

-Dave