OOPS! I just know you didn't remove the driveshaft for that trip did you? Not all, but most transmissions are lubricated by the engine running (you can do that too for towing) and without that the wheels on the ground still turn the driveshaft into the trans and then without proper lubrication burns stuff up.
Check your owner's manual for that exact vehicle, STD trans, auto, 4X4 or whatever for the towing recommendations. I'm sorry that I don't know the extent of damage but wouldn't be surprised if it was a complete loss for the transmission.
In general vehicles should only be towed for like 10 miles or so and only so fast with wheels on ground. A tow company would know fast what vehicles can be towed what way and might know of the damage extent possible.
Tough way to learn that - sorry,
T
Tom Greenleaf - MetroWest Boston - USA
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http://www.autoacsystems.com/tomgreenleaf/