I replaced the alternator on my 2013 F 150 XLT 4x4 5.0 engine at 257000.
everything went smoothly although it was COLD and it too me 2 1/2 hrs.
Fired up charged all good. Now two days later my speedo will go to 0 and trans will shift int 5 while driving. pull over and stop start moving again (not shutting off) and trans shifts to 3 then right to 5. shut it off and all is good.
Has happened 3 times in 72 miles over 2 days

 

If the problem was not there before replacing the alternator, then we need to recheck our work.

Part of the recheck includes checking the fit of the contacts on the alternator plug. If the contacts inside the plug become loose, it can create this type problem.

 

That makes sense. Will recheck alternator plug and report back