The remanufactured hydraulic pump on the John Deere 4020 tractor is part of the hydraulic system. It’s easy to install and comes with many replacement parts. However, there are a few things to keep in mind before purchasing a kit. The following are some of the most important tips to remember when buying a rebuild kit for your tractor. You can also read our article about the different components of a new hydraulic pump to learn how to replace them.