How do you adjust the drive cable on a troybilt self pro pelled md# 12A-446A711?????

Unfortunately, you cannot adjust it. If you have an extra space to move it lower than it was on the handle you can do that. You might have to get a new cable. Or the belt may need to be replaced. Do you hear a grinding noise when you try to engage the self propel? If so the transmission may have gone out. The most common problem is that the belt has jumped off from where it needs to be and it is no longer turning. To check to see if the belt is off, you will need to put the mower on its' side, the side with the oil level check is the correct one. You will need to loosen the cover over the drive belt. This is done by loosening one or two bolts that hold it in place.The bolts should have 3/8 hex heads. You may have to maneuver the cover a bit to see if the belt is in place. If the belt has jumped above the pulley for the self propel then you will have to install a new belt.