I have a 88 d 100 and the bench seat does not go all the way back. I had a 86 d150 and that seat did. I have nothing blocking it and have enough room for what is behind the seat. Why can't it go back more? What about your seat? thanks

 

Are both catches releasing? Might want to pull the seat out, remove the tracks and clean them.

 

Just to elaborate. The drivers side catch is operated by the seat adjustment lever directly because they are the same piece of metal. The passengers side catch is operated by a wire that connects the two catches. This wire can stretch or even break causing the passenger side catch not to disengage. This wire is just twisted around on itself at the attachment points and is made of very hard metal and therefore it is very brittle. It will almost always break if you try to adjust it.