My F-150 , 5.0 v8 has 105,000 miles on it and I have had a intermittent shift problem since about 70,000 miles. I have had it to 4 different dealers and no one has found a solution. The last dealer seemed to have some clue and found broken springs in the 1/2 accumulator pistons TSB99-18-05 &TSB97-11-11. This truck has been well cared for since new, all service schedules followed including transmission fluid and filter changes every 30,000 miles and every 10,000 for the last 2 becuase of maintenance.The truck will shift down for no reason (decellerating, going up a grade, or on level ground, with O.D on or off) it shifts from 4 to 2nd and seems to hang there & not shift up again. This problem is intermitant. Does any one have some ideas? I and losing patience!

 

I've seen several 4R70Ws that do this. In each case it was the Transmission Range Sensor (TRS). That is the sensor on the driver's side of the transmission, where the shift cable attaches.

As the sensor ages the internal resistance increases, and it gets high enough that the PCM reads it wrong and causes the transmission to shift.

Change the sensor and you problem will be history.

Mark

 

my 4r70w does the same thing. But what about the speed sensor? Can it cause the same malfunction. The scanner said "check wiring and fuses" but no codes. !