RV Repair: 1999 4R100 ford transmission, triton v10, ford transmission

Question
Hi Bill, driving on the level in overdrive at 59 to 61 mph the trany will shift down into third, then back into overdrive. Doesn't do it all the time, every couple hundred miles. Has done it in both cruise and peddle driving. (engine is Triton V10).            Thanks for your time, Wayne

Answer
Hi Wayne:
That transmission goes into overdrive right around that speed. Try driving at a speed higher or lower. If it does it then also then there is a problem with the speed sensor or the overdrive control. If it does not do it at a higher or lower speed then you are driving at a speed too close to the overdrive shift point. At that speed any change downward with the fuel lingage will force the transmission to shift out of overdrive, whether you do it manually or the cruise control does it.
Bill