Went to Cushing Oklahoma on Fri and Sat to help Scott Kuhns Cat thirty.  It had developed a "growl" in the rear end region.  When it was unloaded off of the trailer, it locked up momentarily,  then went on.  
Scott had an old service book, and as it turns out, in order to look at anything on the rear end, the platform, seat and such,  the tracks and track frames need to come off. Luckily, the person whose shop we were at had plenty of tool, torches and hoists!
Platform seat and Tracks and frames out of the way, on to the trans top. With the top off, nothing out of ordinary was found.
Saturday morning and on to the final drives, again thanks for the torch! Both finals out of the way and nothing obviously wrong yet. Ring gear and steering clutches, nope not yet! Into the transmission!
More torching and discussing and top shaft out. Nope!
More torching and bottom shaft out. YEA!  Front bearing on bottom shaft had lost the cage around the balls in the bearing. Bits of bearing cage floating around the bearing retainer.
I think Scott is in the market for gaskets, seals, and bearings at least.  Maybe a parts tractor with "good" transmission.