89 F-150 4.9 manual transmisson/overdrive
 

Hello
I can not get my 5 speed manual transmission to shift into overdrive. Someone once told me there is a white plastic piece that is broken inside the top of the shifter that would also make it difficult to shift into reverse. This was true for one or two times but is okay now (that is, shifting into reverse). Is this true? Can I fix this myself or leave it for the pros? Is this a common problem? Need some help.

Big Daddy 51