So I've been searching for an answer for a couple months with no success.
My Trans will not go into Reverse or Park. It stops at Neutral. No the cable isn't messed up as I still can't get it into Park or Reverse with the selector arm on the trans. I've pretty much condemned the trans unless someone knows what's up. Also it drives fine in all of the forward gears.

 

You might get lucky,.... If it's NOT the cable or Park-Lock cable than the linkage inside the tranny might have busted. I had something similar happen to me before. Once I dropped the tranny pan I found that the linkage/arm (where the cable attaches ) was screwed up and I needed to replace it before the tranny should shift properly again.

First - re-check the cable to BE SURE ! disconnect it at the tranny and then work it though it's full range - just to BE SURE ! If the cable really is OK;
get yourself a tranny filter and some fluid,... drop the pan and inspect the linkages to see if that stuff looks OK. Fingers crossed for you dude !!! I've got some spare 700R4 internals stashed in the garage 'just in case' so feel free to send me a PM if you need any of those small parts. ( Pics help ! )