Very true, Jerry. In a few words, if the gears are too tight they will whine. If they are too loose they will rattle. Gaskets come in .010-.030 thickness. Spacers come in .062, .100, 125, and .250. If one is expereinced a proper backlash "feel" can be used with good results. Spacers with gears in them are used on certain applications and for changing the rotation of PTO's. Most of the added specers or shims call for increased stud length. Copper washers should also be used with PTO's and not lock washers which can break the case flanges.
A great many of the new PTO's are aluminum cases but if direct mounting a hydraulic pump care must be taken to insure that the PTO is of sufficient strength to hold the weight of the pump. One thing sort of leads to another and that is why it is very important to not attempt just bolting something on. It can be extreemly expensive.
