There are a few things you need to do in order to adjust a John Deere hydrostatic transmission. The first thing you will want to do is check the oil level. You will want to make sure that the oil is at the correct level, as this will ensure that the hydrostatic transmission is working properly. Next, you will want to check the drive belt. The drive belt should be tight and not loose. If the drive belt is loose, it can cause problems with the hydrostatic transmission. Finally, you will want to adjust the pressure relief valve. This valve controls the amount of pressure that is released from the hydrostatic transmission. If this valve is not set correctly, it can cause problems with how well the hydrostatic transmission works.