727 Shift question?

I had the exact same problem when I had my 727 rebuilt. I put a kit in it years ago and the trans probably had 100,000 mles on it when I put the B&M kit in it, so everything was very loose. When I had it rebuilt last year mine did the same thing yours is doing. Here is a link to the thread I started and all the responses and what I ended up doing to fix it. Hope this helps:

http://www.forabodiesonly.com/mopar/showthread.php?t=169957