When i drive on the highway for 65 to 80 the transmission is shifting hard and often from 3rd to OD when i get on it , when i drive around under 50 no problems!
This just started a week ago i was driving along on the highway at 70 and all of a sudden when the truck downshifted the engine shut off, it started right back up again but continued to shift alot and hard all the way home.
I did not get any check engine light but i am going to have it scanned for codes this week.

My truck is a 2001 supercrew 5.4 with only 35,000 miles
Any help would be greatly appericated