I have a '98 F150 4x4, stock size tires, E4OD. The problem I've been having for 4-5 years now is that my transmission goes into "Safe mode" and 100% line pressure when the truck gets over 55mph. The transmission shop & Ford tell me there is a code coming from the speed sensor on the transmission. It has been replaced twice and nothing has changed. The problem also causes my speedometer to read incorrectly after 50mph or so. At interstate speeds I can let off the gas (with a load in the bed) and the speedometer will show that the truck speeds up by 3-4 mph then will jump down. When the speedometer reads 65mph I'm actually going 75mph+. A while back when the dealership had it for a week they said there is a TSB regarding the fuse panel and that called for it to be replaced, however everyday they tried to get the truck to get some sort of speed sensor code or error they couldn't. They didn't want to replace the fuse panel and not be the issue. Has anyone ever had this problem or heard of it? The transmission has been rebuilt a few times in the past. Once it goes into 100% line pressure it will stay that way until I turn the truck off and restart it. The trans shifts so hard that it jerks the truck. I do not have a chip in it either. Any help would be appreciated.