This is the second time this has happened. The first time was about 11 years ago and the owner found a local guy to repair it. I wasn't around when the repair was made but was told that the guy replaced a broken or maybe sheared pin somewhere in the tractor where he didn't have to split it or do anything major to take apart the tractor. I was told this by the owner at the time. He didn't even know what the guy did or where the pin was located,only that it wasn't to difficult for the guy to repair and didn't take a long time to do. The repair lasted for approximately 15 - 20 hours of pulling a disc spread across 2 years until the 770 stopped moving again with the same symptoms as before,however now the owner was in his early 80's and lost the phone number for the guy who made the repair and also decided to not find someone else to look into it again and just stop using the tractor all together. That was in approximately 2008,he put a cover over the exhaust and never touched the 770 again. Now he wants to sell it and I am asking your advice to see if anyone has any insight as to what might be the problem/solution. This is a tricycle front 770. Thanks for reading this and for your help.