Last Fall, I had the same problem. I'd been using a piece of mild steel dowel, cut to fit. Being mild steel, it wore pretty quickly, so the slop returned. A transmission guy in Dallas told me to take one of the bearing rollers that line the inside of the input shaft pocket (Where the nose of the output shaft fits in) and use it. Correct diameter, correct length. Also, it's hardened steel, so it doesn't wear. Did that seven months ago, and it's still going strong.