1999-1/2 & Later T-Series and W5 with Isuzu MLD6Q 6-Speed manual transmission The 5th/6th- synchronizer hub is press fit to the output shaft. GM-22873 is used to press the 5th/6th- synchronizer hub to correct depth for proper synchronizer and transmission operation. GM-22873 is required to install the 5th/6th- synchronizer hub without damage to the hub or the output shaft. After the 5th/6th- synchronizer hub is placed onto the output shaft, GM-22873 is installed over the hub, and used with a hydraulic press to install the hub into position.