The pinion bearing on the GMT900 trucks has been improved, and it no longer has a step on the bottom, allowing GM-22912-A to be used alone to remove the pinion bearing. GM-47688 consists of two halves that encircle the bearing and are used with GM-22912-A and a hydraulic press to remove the bearing without damage. The bearing may need to be removed and reinstalled several times during the shim selection process.