Tools Required

1. If 4WD vehicle, install the rear case assembly.

1.1.	Ensure the reverse idler shaft is lined up with the hole in the case.

1.2.	Rotate the case back and forth while pulling down.




2. If 4WD vehicle, install a new main shaft rear bearing retaining ring.



3. If 2WD vehicle, install the following components:

3.1.	Install the J 36515-10 through the bolt holes in the rear housing.

3.2.	Screw the threaded cable ends into the mainshaft bearing retainer.

3.3.	Position the notch in the bearing retainer towards the oil delivery tube assembly.

4. Fill the countershaft rear bearing race with J 36850 or equivalent.
5. If 2WD vehicle, install the rear case assembly.

5.1.	Ensure the reverse idler shaft is lined up with the hole in the case.

5.2.	Align the shift forks shift rail opening with the rear case.

5.3.	Rotate the case back and forth while pulling down.

5.4.	Pull up on the J 36515-10 while installing the rear case.

5.5.	Loosely install a rear bearing retainer bolt in the open hole. This is to hold the bearing retainer in place when the J 36515-10 is removed.




6. Remove the J 36515-10 .




Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

7. Install the 3 mainshaft rear bearing retainer bolts.

Apply threadlocker GM P/N 12345382 (Canadian P/N 10953489) or equivalent to the bolt threads.

Tighten
Tighten the mainshaft rear bearing retainer bolts to 22 N·m (16 lb ft).




8. Lay the housing assembly down on a work bench.
9. Remove the rear housing assembly from the J 36515 , the J 36515-15 , and the J 36515-16 .



10. Install the reverse idler shaft support.
11. Apply threadlocker GM P/N 12345382 (Canadian P/N 10953489) or equivalent to the reverse idler shaft bolt threads.
12. Line up the bolt threads in the idler shaft support with the bolt hole.
13. Install the reverse idler shaft bolts.
14. Hold the reverse idler gear shaft against the idler support while tightening the bolts.

Tighten
Tighten the reverse idler gear shaft bolt to 22 N·m (16 lb ft).




15. Install the 3rd/4th speed gear shift fork onto the 3rd/4th speed gear synchronizer sleeve.



16. Slide the shift shaft through the following parts:

16.1.

The 3rd/4th speed gear shift fork

Ensure that the detent reliefs in the shift shaft point to the front of the transmission.

16.2.

The shift lever

16.3.

The block-out bushing

16.4.

The 1st/2nd speed gear shift fork

16.5.

The 5th/Reverse shift fork

16.6.

The rear case bushing and bearing

16.7.

The shift socket




17. Install a new short roll pin into the shift lever. The end of the spiral must face toward the direction of the thrust.

17.1.

Rotate the shift shaft and the shift lever/block-out bushing assembly. Ensure the roll pin holes are aligned and horizontal.

17.2.

Support the shift shaft while installing the roll pin.

17.3.

Install the roll pin flush with the shift lever.





Important: On the S/T trucks, the shift shaft has only one hole.

The C/K trucks have 2 holes on the shift shaft. Use the front roll pin hole (1).
18. Install the shift shaft, the shift shaft socket and the new long roll pin.

18.1.

Align the holes in the shift shaft socket and the shift shaft.

18.2.

Drive the roll pin flush with the bottom of the shift shaft socket.




19. Install the detent spring and the ball plunger into the hole in the shift lever.

19.1.

Rotate the shift shaft counterclockwise. The shift lever should be almost into the 5th/Reverse speed gear insert notch.

19.2.

Install the spring (1) and the ball plunger (2) into the shift lever.

19.3.

Rotate the shift shaft until the shift lever aligns with the 3rd/4th speed gear insert.

Important: The transmission must remain in 3rd or 5th gear in order to prevent losing the shift shaft lever spring and plunger.

20. Shift the transmission into 3rd or 5th gear.




Important: The smaller diameter of the bearing cage goes into the bearing race.

21. Install the countershaft bearing onto the counter shaft.

Ensure the smaller diameter side of the bearing is positioned toward the front case half.

22. Fill the front countershaft bearing race with J 36850 or equivalent.



23. Apply gasket maker GM P/N 1052943 (Canadian P/N 10953491) or equivalent to the front housing sealing surface.
24. Align the dowel pins in the clutch housing to the rear case.
25. Install the clutch housing to the rear case.



26. Install the housing bolts.

Do not tighten the bolts.





Important: Do not scratch the sealing surface on the input shaft while installing the retaining ring. Minor scratches may cause premature seal failure.

27. Install a new retaining ring on the input shaft. It may be necessary to pull out on the input shaft in order to install the retaining ring.




Important: Do not allow sealant into the oil return hole in the housing or bearing retainer.

28. Apply RTV sealer GM P/N 12345739 (Canadian P/N 10953541) or equivalent to the inside edge of the bearing retainer mating surface.



29. Install the input shaft bearing retainer to the housing with 6 bolts.

Align the retainer oil drain hole with the drain hole in the housing.

Tighten
Tighten the retainer bolts to 14 N·m (10 lb ft).

30. Rotate the input shaft a few turns to align the transmission bearings and to test for any excessive binding.
31. Tighten the front to rear housing bolts.

Tighten
Tighten the housing bolts to 35 N·m (26 lb ft).




32. Install the following components:

32.1.

The shift shaft detent plunger

32.2.

The shift shaft detent spring

32.3.

The shift shaft detent plug

Apply pipe sealant GM P/N 12346004 (Canadian P/N 10953480) or equivalent to the detent plug.




33. If 2WD vehicle, coat the speed sensor O-ring with Synchromesh Transmission Fluid GM P/N 12345349 (Canadian P/N 10953465) or equivalent.
34. Install the speed sensor, O-ring, and bolt.

Tighten
Tighten the bolt to 16 N·m (12 lb ft).




35. Install the backup lamp switch.

Apply pipe sealant GM P/N 12346004 (Canadian P/N 10953480) or equivalent to the threads of the backup lamp switch.

Tighten
Tighten the switch to 37 N·m (27 lb ft).




36. Install the shift shaft detent pin.

Tighten
Tighten the detent pin to 25 N·m (18 lb ft).




37. If S truck, using the J 45379 , install the output shaft seal.



38. If C truck, using the J 36503 , install the output shaft seal.



39. If 4WD vehicle, install the J 36502-2A on the output shaft.
40. Install the output shaft seal using the J 36502 .
41. Remove the J 36502-2A from the output shaft.



42. Fill the space between the seal lips with chassis grease.
43. To prevent the transmission fluid from spilling while installing the transmission into the vehicle, fill the transmission after installing with Synchromesh Transmission Fluid GM P/N 12345349 (Canadian P/N 10953465) or equivalent.