1992 voyager 3.0 questions

2 questions. My speedometer and odometer do not work? i disconnected the negative battery cable and this did not fix it (im lost)?? other qeustion. Sometimes when i am driving, when i hit the brakes hard the van will stall? it restarts fine, but i am very confused on this one.

Well, the second question.....I think it has to do with the power break booster. not sure what exactly though, sorry.