Usage:
All Powershift Transmissions
A number of field reports have shown early failures of new transmission pumps installed in machines that have operated several thousand hours. In most of these failures, the drive gear in the pump wears into the rear manifold (cover) of the pump. See Illustration 1. This type of failure is caused by the drive gear being forced into the manifold or cover. This is due to a wear step in the mating, driving gear or shaft which restricts free float of the pump gear.
Illustration 1. Location where pump gear wears into the manifold (cover) of the pump. Typical pump shown.
This wear step occurred during the previous hours of operation, when the splines or tang on the shaft of the original pump wore notches in the splines or slot of the mating driving gear or shaft. See Illustrations 2 and 3.
Because of tolerances in shaft length, the end of the new pump shaft can make contact with the shoulder at the end of the notches worn in the drive gear or shaft when the pump is installed. Under load, this contact causes an axial force against the pump shaft and gear. As a result, the pump gear cuts into the face of the pump manifold (cover).
To prevent this problem, carefully inspect the driving gear splines or the driving shaft slot for wear before installation of a new pump. When enough wear is found for the new pump shaft to hit against (approximately 0.38 mm - .015"), install a new driving gear or shaft. In an emergency, the end of the new splined pump shaft (including the chamfer) can be ground off approximately 0.25 mm (.010"). Generally, this will be enough to prevent possible problems. Do not shorten the driven tang on a tang type pump.
Illustration 2. Location of wear in tang slot of drive shaft for shaft driven pumps.
Illustration 3. Location of wear in splines of drive gear for gear driven pumps.