Was using the Case 2090 to pull gravity wagons one night last week. All short distances at slow speeds - tractor wouldn't have even gotten warmed up. Pulled up to the auger and shut tractor down for the night and heard a large bang. Sort of a haze/smoke around the tractor. Thought it have been a hydraulic hose or pipe under the tractor. It was late so I just quit for the night. Next day I started the tractor up and everything worked fine. Later in the day I noticed the transmission filler cap was off. So, I assumed the bang was the cap blowing off and letting some kind of pressure off. The next day while pulling a load I smelled an odor and and smoke was coming from the transmission filler (no cap - can't find it after it blew off). I would have basically just started the tractor up and would have moved a couple hundred feet. I stopped and smoke was still rolling out. I wondered if it was related to the PTO so I moved the knob and could hear a difference in the engine and after pulling it up and down it seemed to disengage and not drag the engine down and the smoke went away. Now the PTO runs constantly. I have not tried to hook up a large PTO load to see if the PTO stops or if it will carry a load. The PTO hasn't been used in years. I did pull the knob up a couple weeks ago and lubed the cable when I was lubing the engine stop cable. I assume I moved it up and down to work the cable lubricant in and that I left it in down position. This smoke event also must have happened the night the filler cap was blown off. Any idea what has went wrong. Transmission works just fine. Did need to change the transmission/hydraulic filters fairly soon as I had weak/no power steering, etc. Hydraulics worked excellent after filter change. Haven't had any smoke coming out of the transmission filler, but the PTO runs continually. Could this happen if the PTO knob was slightly engaged? What happened? Did the PTO brake work against the PTO clutch? Is this something that happens? What did I damage? What are the repairs? Thanks guys.