First rule of externally heating your transmission is you can not add heat to the transmission in an uncontrolled manor. You will fry it. The #1 killer of transmissions by far is heat.
My current transmission is the GM TH700R4, its current cooler setup does what its name implies.
It cools the transmission, too much at times in the winter.
Also being a light duty transmission it has proven to me that it can not pump enough fluid through its cooler circuit to properly cool its self during the hot summer. I am going to fix all that in the next revision.
Any one up north or on the east coast is thinking what I was thinking before I moved to New Mexico and that is they don't really even have winter.
Well so far every year has produced numerous winter nights at, near or below 0'F. Some years more than others. The coldest year so far has had a full week of -10'F nights in a row with a -16'F night that froze almost everyones pipes.
I am going to harness 2 sources of heat for the transmission, internal and external. Keep the internal heat in side the transmission when its cold out and add external heat when the transmission is in need of warm up.
When it gets near freezing my temperature gauge doesn't move past the lowest mark, 100'F. This should fix that.
External transmission heating will be accomplished 2 ways. With engine heat and external vehicle power.
Trapping internal heat will be accomplished by installing a thermostatic valve on the transmissions existing cooler circuit. When the transmission fluid coming out of the discharge port is below 120'F it will all be looped through the hot side of the valve to a plate heat exchanger and right back into the transmission.
My suburban has a "transmission cooler" on the hot side of the radiator. So it is useless for warming up the transmission at the same time the engine is warming. This set up will only give up heat to the transmission only once the thermostat starts to open, as the engine reaches operating temperature. On very cold days the thermostat doesn't even open or doesn't stay open.
On the flip side New Mexico gets well above 100'F every year.
The thermostatic valve will have a cooling side in addition to the hot side of the valve. Once the transmission heats up above 120'F the thermostatic valve will start to activate and the cold side of the valve will start to include more fluid from the front mount coolers (already installed) as it closes off the hot side of the valve and its hot fluid.
The thermostatic valve will function to maintain fluid temperature between 120'F and 140'F.
Heating with external power will be done by direct heating of the fluid with a repurposed engine block heater. I have found the stick on heaters to be almost useless.
I will use a 400 watt Kat's engine block heater. The one I found uses a 3/4NPT connection. So you could use this block heater almost any where.
I need to test this to make sure it wont scorch the fluid.
To add heat from the engine coolant to the transmission I am going to put a plate heat exchanger on the hot side of the thermostatic valve.
I impulse bought a 30 plate heat exchanger off ebay just before typing all this.
Its 316SS, pressure rated for 445psi and temperature rated for 300'F. Which should be sufficient. It has male 3/4NPT ports on all 4 corners. The 3/4NPT ports are perfect for hooking up coolant, but I will weld a 304SS 1/2'' pipe coupler cut in half on to the ports I am going to use for hooking up transmission fluid.
The vessel that I am going to use to house and attach all this new equipment is a Moroso aluminum transmission pan. The Moroso has 2 drain plugs. Why they put 2 drain plugs I do not know but I can reuse them.
The pan is going to be painted black to increase infer red emissivity.
That little problem I mentioned in the start of the post where the transmission doesn't pump enough fluid to cool its self will be fixed by adding an external 3.2GMP seaflo oil pump to a stand alone cooler. Controlled by 150'F Reznor fenwal thermoswitch and manual switch.
This thermoswitch will also disable the external powered fluid heater.
I already have the horizontal mount auxiliary trans cooler with fan installed, just need to get a good supply of hot fluid to it.
Kat's part number: 11409, $40
These Reznor fenwal switches are cheap on ebay right now. $10 each
30 plate heat exchanger $82.
Seaflo oil transfer pump $80 (only for cooling)
Thermostatic valve $?? (I have not found the one I want to use)