94' E150 c6 trans will not shift into P or R

Upon arriving at the resteraunt last saurday night my wifes van developed a problem with the transmission. It wont shift out of drive and into either park or reverse. I've allready checked the linkage, by taking it off of the shift lever on the side of the trans. the linkage works fine. The trans lever itself will only click through three detents, 1st,2nd,and3rd gears. It will however go into neutral.
Im stumped, the only thing I can think of, is that it might be tied in with the brake pedal releas mechanisim for the shifter
Also it needs the Intermediate band adjusted,(wich I can perform) I dont know if these two could possibly be related or not.:banghead:

sounds like something came apart on the inside causing the detent not to go toward reverse and park. you can see the detent when you take the pan off.