I just testdrove a 1998 F150 supercab with a 4.6 V8, automatic. It seemed well maintained at 102,500 miles. However, the overdrive was problematic. I noticed an automatic shifting back and forth of 4th and overdrive at speeds above 45 mph. Is this a serious transmission problem? With overdrive turned off, the truck shifted and drove smoothly. I can purchase it for $7,500. Is it worth it at that price even if the transmission needs rebuilding? I plan on towing 3000 lb boat and trailer. Thanks.

 

Were you driving up a slight hill when this was happening? Heavy truck with small engine often means a lot of hunting between gears when climbing hills. INHO, if you're looking at a truck of this age for towing, you should look for a 5.4 which has more reserve power and a heavier-duty transmission.

 

How high a speed and how was it on a flat suface.If it does it at 45-55 with light throttle it could be tranny shutter.I think it has to do with the torque converter slipping and can cost big money for a rebuild.You can't tell on hills like PaulC said.My 97 7700 had it and i was told by my mechanic to dump it or pay up.I traded at the dealer on a 98 XLT.The 97 was sent to wholesale as I couldn't sell it and screw someone.I was told it will get worse over time.Could also be a COP.Theres a lot of threads on tranny shudder so do a search.