Tedy, I'd try cleaning out and replacing the shifter gear box grease, if you haven't already. I've had no problem with it this winter since I replaced it before it got cold, but Yelostn78 (I think) took his truck with the three speed out on the road for a little while and couldn't get it to shift at all, and come to find out, the grease in the box was so old that it had froze solid.
Yes check this first, I bet the grease is old or overfilled, I would coat everything in the stearing gearbox with your finger, dabbing on the grease, and then check it from time to time, it is only four screws, and Since servicing mine it shifts like a dream in all temperatures.
