Sounds like the axle bearings locked up -happend to me this past december. I was on my way to plow snow, I started slowing down for a stoplight and the truck got away from me like I was on black ice - startled I was!
After I came to one scary stop, I went to make a left hand turn and all it wanted to do was "donuts"!
After doing "donuts" to get my truck to the shoulder of the road, I had a buddy hook a chain to my truck and drag me a mile to my shop.
Finally got the thing in the shop and realized my left rear wheel wouldn't turn, hmmm, thats odd. Pulled the wheel figuring my shoes froze to the drum, nope. Pulled diff cover and drained oil, nothing odd came out. Finally went to pull my axles out, and then I noticed the drivers said was all jacked up.
I see you mentioned you had recently performed a rear diff service, sounds like it might not have been filled all the way - you need to jack the truck up side to side so you can verify outer axle bearings have been properly lubed.