I thought I had a transmission problem and found that a new trans was no longer available. I was able to find a used one and recommend Joe's Outdoor Power. 4 bolts removed the seat, 6 bolts and pedal retaining pin removal took off the body. 4 bolts and center bolt removed the trans fan and driveshaft from engine and trans. Uncoupled 3 hydro fluid lines and bottom linkage, then 4 bolts allowed the removal of trans.
After install of replacement trans and added fluid, I started it up and found the same problem. "It was the driveshaft and boss connector that had stripped out!" I was able to obtain these two parts from Kubota and installed.
The machine has never sounded so good... It's better than new. I mis-diagnosed the problem because of non-movement and noise I thought was coming from trans.
After body was off and trans replaced, I could then tell it was the drive shaft spinning inside of the boss near engine. Still pleased with the outcome and hope many more years of service from a great machine.