I have a 2007 f150 with a 4.6 and an automatic transmission. When I accelerate and the truck tries to shift it starts shaking violently. The entire truck starts shaking and hopping like the rear tires are locking up. If I stop and put the truck in park and then restart it doesn't happen again until the truck tries to shift under acceleration. I got it home by just starting slow and then very gradually gaining speed. When I did this it worked fine and drove for several miles. I don't know much about automatic transmissions but it seems like the truck is in 2 gears at once or like it is trying to put itself in park. Does anybody know what could cause this problem or what I can do about it. The fluid is at the proper level.

 

Mileage? Have you ever changed the spark plugs? My 5.4 acted like the transmission was slipping and turned out to be a misfire.

 

It has 142,000 or so miles on it. I had a problem with the truck shaking a couple months ago and had all of the plugs and coil packs changed. That solved that problem. This turned out to be the midship bearing on the driveshaft going bad. The only problem with this is you can't replace just the bearing, you need a whole new driveshaft. But $650 for a new driveshaft is far better than having a major transmission problem. Thank you for the help