Assemble

Exploded View Of Type 8, Hummer (ET) Transmission:

Installing Shift Rail Seal:

1. Seat new shift rail seal in rear of case.
2. If shift rail bushing was removed, drive a new one into place with a 9/16 inch socket and extension.
3. If 1st-2nd synchronizer was disassembled, slide the sleeve over hub making sure shift fork groove is toward front of shaft. The sleeve and hub are select fit and must be reassembled with etch marks in same location. Locate an insert in each of three slots cut in the hub. Install insert spring inside sleeve beneath the inserts. The tab on end of spring must locate in the section of an insert. Fit the other spring to opposite face of synchronizer unit, being sure spring tab locates in the same insert as the spring just installed and is in the same rotational direction. Looking down at the synchronizer, the tab end of one spring should be in line with the tab of the spring on the opposite side. Oil all parts at time of assembly.
4. Assemble a blocker ring on 1st gear side of 1st-2nd synchronizer. Apply grease to cone surface of 1st gear. Slide 1st gear onto output shaft so that cone surface engages blocker ring.
5. Position spacer on shaft making certain large diameter is toward rear of shaft.

Determining Snap Ring Thickness:

Output Shaft Bearing Snap Ring Thickness Chart:

6. Place master spacer tool T70P-7154 in output shaft bearing bore of extension. Determine thickness of snap ring required to remove all endplay from master gauge. Then measure width of output shaft bearing outer race with a micrometer. The difference in thickness between master gauge and bearing outer race will determine thickness of selective snap ring. If bearing race thickness is more than that stamped on master gauge, the snap ring thickness must be decreased to closest available ring. If the thickness is less, the snap ring thickness must be increased.
7. Position selected snap ring and the bearing on output shaft. Position tool T69P-4621A on shaft, then place assembly in a press and press bearing into place. Secure bearing with thickest snap ring that will fit groove in output shaft.
8. Slide synchronizer sleeve over hub and locate an insert in each of the three slots cut into sleeve. The sleeve and hub are select fit and must be reassembled with etch marks in same relative location.
9. Install an insert spring inside synchronizer sleeve beneath inserts. The tab on end of spring must locate in the U section of an insert. Fit other spring to opposite face of synchronizer unit, being sure that spring tab locates in same insert as spring just installed and is in same rotational direction. Looking down at the unit, the tab end of one spring should be in line with the tab of the spring on the opposite side.
10. Position the 2nd gear and blocker ring on output shaft so that dog teeth face rearward. Install washer and snap ring. Position 3rd gear on output shaft so dog teeth face forward. Apply grease to cones of gears and assemble blocker ring on 3rd gear cone.
11. Position 3rd-4th synchronizer on output shaft with hub boss facing forward.
12. Position tool T69P-4621A so that it butts against boss on synchronizer hub.
13. Place entire unit, extension end up, in a press and push synchronizer unit onto output shaft as far as possible.
14. Retain 3rd-4th synchronizer to output shaft with snap ring. Pull up on synchronizer assembly so snap ring is tight in its groove.
15. Prior to assembling output shaft and extension housing into the case, apply lubricant to cone of gear and place 4th gear blocker ring on input shaft gear cone.

Installing Speedometer Drive Gear:

16. Press speedometer gear onto shaft with tools shown, until dowels just contact bearing outer race.

NOTE: The dowels must contact bearing outer race to properly locate speedometer gear on shaft.

17. Coat bearing bore of extension housing with lubricant and install output shaft in housing. It may be necessary to tap shaft with a plastic hammer while holding the two synchronizer sleeves firmly to prevent sleeve separation from hubs. Secure it to extension with selective snap ring that was previously installed.
18. Press bearing on input shaft with snap ring groove toward front of shaft. Secure bearing to shaft with thickest selective snap ring.
19. Slide spacer and dummy shaft into countershaft gear. Position a thin bearing retaining washer at each end of dummy shaft. Coat bearings with lubricant. Load long bearings into small end of countershaft gear and short bearings into large end of gear.

NOTE: The 74WG transmission has 19 bearings at each end and the 74WT, 75WT & 78ET transmissions, have 21 bearings at each end.

20. Fit a thick retaining washer over each end of dummy shaft. Coat each thrust washer with lubricant and on 74WG, 75WT & 78ET models position one on each end of dummy shaft and on 74WT models, position two thrust washers on ends of dummy shaft. Make sure the tabs are in the same relative position so they may engage slots in case when gear is lowered into place. Loop a piece of rope or wire around each end of gear. Carefully install the countershaft gear with rope through rear end of case and lower the gear into place being careful not to disturb thrust washers and making sure that tabs engage slots in case.
21. Apply lubricant to reverse idler gear shaft. If selector lever relay was removed, position on pivot pin. Secure lever on pin with spring clip. Hold gear in the lever with long hub toward rear of case. Slide reverse idler gear shaft into place and seat shaft in the case with a copper hammer.
22. Install a new seal in input shaft bearing retainer.

Installing Input Shaft Gear:

23. Assemble input shaft to case using a new retainer O-ring. If necessary, tap outer race of bearing with copper hammer evenly until outer snap ring is seated against case.

CAUTION: Do not tap on input shaft as this may damage races or bearings.

24. Carefully slide 3rd-4th speed synchronizer sleeve into 4th speed position (forward to provide clearance).
25. Position new gasket on extension housing.
26. Lubricate input shaft pilot bearing and install in shaft. Slide extension housing and output shaft into place being careful not to disturb 3rd-4th synchronizer.
27. Align cutaway in extension housing flange with countershaft bore in rear of case.

Installing Countershaft:

28. Lift countershaft gear into place with cord or wire, then slip countershaft into place making sure both thrust washers are in place. Make sure that flat on countershaft is toward top of case and in horizontal position. Then tap it into case with brass hammer until front of shaft is flush with case.
29. Place shift forks in synchronizer sleeves. Position interlock lever and install new retaining pin. Lubricate shift rail oil seal and slide shift rail through extension housing, transmission case and 1st and 2nd speed shift fork. Position selector arm on rail, then slide rail through 3rd and 4th speed shift fork, then through front of case until center detent is aligned with detent plunger bore. Install new retaining pin in selector arm.
30. Install detent plunger, spring and plug with sealer.
31. Install new access plug in rear of case.
32. Rotate extension to align bolt holes, then install bolts loosely. Before tightening bolts make sure shift rail slides freely in bore.
33. Position new oil seal in input shaft retainer so tension spring and lip face the case. Drive seal into position.

Installing Input Shaft Gear:

34. Position new O-ring in groove in face of case. Install input shaft bearing retainer to case. Be sure that oil passage in case is in line with oil groove in retainer. Apply sealer to bolts and attach to case.
35. Reinstall clutch release bearing.
36. Apply sealer to new extension housing plug and install it.
37. Install top cover with vent toward rear. Make sure that sealer is applied to bolt over detent plunger bore.