Pinion Shaft Locking Tool
Here's a clever idea for a tool to lock the pinion shaft so its bolt can be tightened. It is a worn-out slider welded to a two-foot length of 3/4" square steel tubing. I got this idea from Mike Lesniak's excellent video on 901 transmission rebuilding. This works only on a five-speed box; the reverse-slider hub of a four-speed has different dimensions.