Hello, this is my first post, so bear with me. I have a m51a2 5-ton dump, multi fuel that has always been very reliable. The other day went to start it after sitting for about a month and started right up, went to let the clutch out and felt like it was in Hi-5th and wouldn't move. Looked into it further and output shaft on transmission doesn't turn when clutch is let out. Did some searching on the site, didn't find anything directly related to this problem, didn't know if it had something to do with the sprag clutch or air valve in transfer case? Oh, forgot to mention could only get gear shifter to move when i moved the transfer case lever in between hi and lo and rocked the truck with excavator and brakes are free. Any thoughts would be appreciated, by the way great site with lots of info, glad i finally got a chance to post.