2002 f150 4r70w, sometimes wont go in reverse, i also have a long 1st to 2nd shift, i am pretty sure that is the accumulator, but the reverse issue is confusing me, when cold goes in most of the time, but after a drive it wont go in, if i get out and rock the truck back and forth it goes in every time i do that, when i rock it, i think i hear a click in the transmission, any help would be appreciated......

 

Reverse is all mechanical linkage for operation.
Look the situation over for worn parts and adjustment..
The trans is mounted so it moves a bit.
Be sure the lever on the Trans is all the way engaged in Reverse.
Sounds like your affecting the linkage mechanically with movement.
Otherwise the trans needs some attention for the other issue.