Random question. Transmission cooling.

[Fitz]

Originally Posted by big_al_71

I live in South Florida and it is super hot during the summer months ....

Everything is relative and South florida ain't hot....not compared to the Sonoran Desert it ain't. There's a lot of folklore in this thread so I ran a little experiment this AM on the way into the office. Before the engine size argument comes up you should know I'm running a 67 stepside with a ZZ572 powerplant tied to a JW Performance built Turbo 400. It takes a big Rad to keep that beast cool. My truck has coolers and temp guages for trans fluid and engine oil as well as the normal engine coolant temp.

First off, the temp of the water in your radiator does not affect the trans oil temp in a radiator with a built in trans cooler. Not at all. The Trans cooler built into your radiator is cooled by the same mechanism as the engine coolant. It is a two fluid heat transfer path; fluid in the tube through the fins to ambient air. AIR is the second fluid not the water on the engine side. The temperature differential between the air and fluid in the tube sets the heat transfer rate through the thermal resistance of the fins. That is why after running 30 miles at 75 MPH on I-10 this morning my engine coolant is steady at 195 degrees, engine oil is rock solid at 220 degrees and the trans fluid temp was steady at...144 degrees. That's 56 degrees cooler than the engine coolant in a BeCool 4 row Rad with built in trans cooler only (no external trans cooler) and it stayed that way for half an hour. What keeps the trans fluid temps down is the radiating SURFACE AREA of the FINS connected to the tubes carrying the trans fluid. My rad is 16 in high and the four vertical tubes carrying the trans oil are spaced 1.5 inches apart and 1/2 in behind the tubes carrying engine coolant. That's 0.75 sq in / fin and there are 108 sq inches in the cooling area of the rad with 10 fins per inch for the trans giving 1080 square inches of radiating surface for my trans cooler. That's why my trans temp is steady and 56 degrees cooler than the engine coolant. If you want to make comparisons between coolers you need to determine the surface area of each fin and multiply that by the number of fins.

You will find that the frame mounted trans coolers can help keep you out of trouble but will never be as effective as a cooler mounted in front of your Rad or one built into your rad...size matters but not the size you think...it's the area of the radiating surface that matters and that's the total area of the fins not the length times height of the cooler you're running.

When it's 115 here in the summer (and yes, Big Al we average 87 days a year above 105 degrees so it's more than a little bit hotter here in the Arizona Desert than South Florida...no ocean here to moderate the temps!) my trans runs cool!