i was coming home getting on the highway and started to shift into 5th and it would go up but it just wouldnt pop in and stay there then i realized 3rd and 1st all are doing the same thing. this is a f series tranny. what could be the problem. ive heard the selector cable may be broke or just came loose. what do you guys think.

 

sounds like the shift cable either borke, came loose, or came completely off. check the cable at the tranny under the hood. if those look ok then go remove your center console and check the cables at the shift lever. if those look ok then you're screwed and its something internal part of the tranny F-ing up. good luck, and i hope its just a bad cable!