While in Florida on vacation, we were driving on I-75 when the Tow/Haul light began flashing, and the trans downshifted to a lower gear and stuck there. It wouldn't shift at all, even after coming to a stop and shifting in and out of gear. When I would take off it felt like it was in 4th or 5th gear and the idle speed was higher than normal when stopped also. We drove to the nearest Ford dealer and dropped it off. Turns out it was a SHIFT SELENOID, and they also replaced the INTERNAL TRANS HARNESS, along with the 2 filters and oil. Many posts on FTE have been about the TEMP SENSOR but not many on the SELENOID so I thought I would post this so others may take note if this should happen to them. Thank heavans for my extended warranty, this would have cost me $733, instead I only paid the deductible. I figure I'm ahead of the game, as the extended warranty cost me $1200. in 05, and have had repairs worth over $4000. so far, and still have another year and a half to go.
Thanks for posting Delawhere?. My truck was acting the ssame way last night, but did some running around this morning and everything ran just fine. No issues. The trans is over the limit for fluid, not sure if that would affect it. Unless if was making the fluid get real hot. Stupid gauge on the dash does not help. SCT will be on the truck soon to monitor it closer.