Is it safe to shift from d to d3 while cruising at high speed?

2011 Ford Focus SE, Bought pre-owned a month ago, Transmission Problems @ 71k miles

• Bought a month ago and I've had nothing but problems from the 4F27E 4-speed. Last week, While cruising at 60-65 mph, It started slipping in and out of OD down into 3rd, then back into OD.. I drove the remaining 2 miles with OD off to keep it from slipping. CEL CODE SHOWED "P0751 Shift Solenoid "A" Performance or Stuck." Next day, Got back in the car to find it was slipping and jerking trying for 4th gear, Had to manually shift it from 2nd to 3rd gear with O/D off at this point. So bought the Shift solenoid A, New Filter, Gaskets, and Mercon V. Flushed the tranny, replaced the solenoid, filter, etc. With no results or improvements except for no CEL. No metal pieces or clutch bands thrown into the magnet, No leaks, No clanking clunking or squeeling, But the old fluid smelled and looked burnt. It was original. 6 days later, It only has 1st and 2nd gear. Sometimes burnt ATF smell, So I have to drop it down into LOW to keep it in 2nd. Wrench light comes on, 3rd grabs but slips. HELP ME

• Answer:

  once that fluid smelled like burnt wires thats bad news your trans is burnt up. trans overhaul time