I have a 88 F150 long wheel base. The other day in town my trucks transmission went out on me. Apparently all of my fluid leaked out and I can no longer engage D 3 2 or 1 BUT the reverse still works. The transmission shop said it needs to be rebuilt but my granddad thinks my linkage is broken. Any opinions ?

 

Think about this.
If the linkage was broken, you wouldn't be able to start it, or shift it into the other positions , it would be stuck in reverse. Simple check would be to go under the vehicle and look.