Got a 2000 7.3L I'm working on. You can pull her into reverse...the engine will lug but you can literally count 1001-1005 before it will even think about pulling. This is the first ford I've messed with as I'm used to Allison's. what could be the cause/causes.

 

So your saying you have a 5 second delay when you put it into reverse before it moves correct?

 

I would venture to say that if the tranny drives fine forward and you have a problem going in reverse it's probably a dirty passage in the valve body and it just needs to be flushed. But if you're having problems shifting after the first shift then I say that you have a tired tranny and it needs servicing I would drop the pan and try and do a filter swap and see what's going on inside by the debris left on your magnet.