Transmission Charge Pump Centerbodies Can Be Modified To Improve The Life Of Pumps With 8-Tooth, Powder Metal Gears Caterpillar

WHEEL LOADERS

Problem:

Some powder metal charge pump gears have fractured without any evident galling or seizing. Improvements have been made in both the basic material and in the geometry of the gears. However, a few failures are still being reported.

Solution:

To increase the life of the pump, the centerbody can be modified to reduce the loads that are imposed on the gears. To modify the centerbody, machine a relief on the two shoulders at the inlet port. (See Illustration 1.)

In production, the relief is cut as a radius, but a small flat made with a file will produce most of the benefits. Illustration 2 shows dimensions and a reference angle for a small flat that approximates the production geometry.

Some benefit could be obtained without removing all of the identified material. The angle shown in Illustration 2, is not critical, but is provided as a target. Ideally, the flat produced by the modification should be perpendicular to the flat faces of the centerbody (the flat should not follow the draft angle of the shoulder).

The modification should be made when pumps for the listed models are rebuilt (until the improved centerbodies are available from the factory). If desired, the same modification can be applied to transmission charge pumps for other models that employ 8-tooth gears.

Illustration 1

Illustration 2

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