Weird rear end lock up

[wjz]

Please help.... Driving home from work today in light sleet/snow. Got up to 50-55 mph...and it seemed like the rear end of the car locked up for a second which caused it to jerk the whole car. It only did this at that speed. I have auto 4x4 and it also did the same thing in 4 high. Any advice on what is wrong is appreciated.

The jerk corresponded with the shift from 4th to 5th gear. I'm guessing trans but hoping for the best.

Thanks for the help

 

[wjz]

I guessed right

Trans went....OD light was flashing on and off....Im in the club now. YAY!