I had the same problems as you with a 2010 F150. And after reading about others over on the F150 forums you're not alone. Mine also did the slam thing coming to a stop. Took it to the dealer twice and the last time they said to just drive it cause they didn't know what was wrong. Basically they said I had a warranty and when and if it broke they would know what to fix.
IMO the 2009-2010 Ford 6sp is the worst tranny for towing. No way to select gears or even lock out OD. It was always hunting for gears and either down shifting or up shifting when not necessary.
Traded the 10 F150 in on a 12 Ram 2500 CTD and after 15,300 miles the tranny is working like a hot knife thru butter.
I've been a Ford lover all my life (60 yrs) but after the 08 and 10 F150's I owned and the issues with the CP4 in the 6.7's I just didn't feel comfortable getting another Ford.
My Ram may not be as quiet, drive as smooth or handle as well as a Ford but so far it's been rock solid for reliability.
I don't think Ford knows how to fix the issues or at worst they do, but won't till it breaks.
