The mule drive is located at the bottom of the mower and attaches to the underside of the John Deere's engine. When the engine is running, the mule drive is constantly turning. To access the mule drive, you must get under the front of the lawn tractor. A mule drive is generally two sheaves that look like pulleys but can be one sheave depending on the John Deere model.
The purpose of the mule drive is to turn the blades on the mower deck when the PTO (Power Take Off) is engaged. Once the operator pushes the PTO control on the John Deere, the mower deck pulleys tighten the belt. As the belt tightens, it tightens around the mule drive, which turns the blades of the mower deck. The number of pulleys located on the mower deck is determined by the number of blades.
The mule drive requires very little maintenance because of the way it is attached to the engine. The drive is not free-turning, like the pulleys on the mower deck, so there are no bearings to lubricate. The sheave or pulley of the mule drive slides onto the end of a shaft or is bolted down to the shaft. The only problem that can occur on a mule drive is wear. Most problems with the drive belt are not caused by a defective mule drive.
It is very difficult to get any publications from John Deere unless you pay for the manuals. Even the John Deere website limits access to the parts catalog and operator's manual unless you pay for access. The best thing to do is go to your local John Deere dealer for help. If you still want an operator's or parts manual, the dealer will have them available, but again, the manuals will probably not be free. You should have received an operator's manual when you purchased your John Deere lawnmower so keep it in a safe place to avoid having to purchase a new one.