If your speedometer doesn´t work that MIGHT mean something probably isn´t connected to it. Usually there´s a wire that goes down to your transmission which also controls your odometer, if it isn´t connected your speedometer will sit at zero, or it could be the same thing my uncle had a problem with... when he had his transmission rebuilt the shop had found the gear that connects to that wire sensor wasn´t spinning because the gear was stripped so his speedometer wasn´t spinning anymore. But since it worked before you took your faces off then it´s probably the wire going to the tranny. I think it´d be a good idea to take apart your dash anyway just to check on all those things and to get to the bottom of this.