The pinion nut has never been off of the truck before, I looked at it and the lock is still in place and it all seems tight. Would I be able to tell it is loose? The pinion turns about 1/2" back and forth, I though this seemed back, but I talked to some people and they said for an older truck that is alright. 
What do you guys think? 
That sounds about right. It will have some movement.
