GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 GMC K Sierra - 4WD 🢒 Transmission/Transaxle 🢒 Manual Transmission - NV 3500 🢒 Mainshaft and Synchronizers
  1. Clean all the parts in a suitable cleaning solvent. Air dry all the parts.

    2. Important: Do not spin the bearings without a lubricant.

  2. Lubricate the mainshaft bearings with GM P/N 12345349 Synchromesh Transmission Fluid (or equivalent).
  3. Inspect the bearings for rough rotation.
  4. Inspect the mainshaft gears for the following conditions:
    5. • Cracks
    • Nicks
    • Chipped gear teeth
    • High spots (small-shiny spots on the gear teeth mating surface) that could cause gear noise
  5. Inspect related gear surfaces like thrust faces and bearing surface diameters.
  6. Inspect the synchronizer sleeves for a sliding fit on the synchronizer hubs. The synchronizer hubs must have a force fit on the mainshaft splines.
  7. Replace a synchronizer hub that does not require a force fit on the mainshaft splines.
  8. Inspect the synchronizer springs and the keys for damage.
  9. Inspect the synchronizer rings for excess wear.
  10. Inspect the synchronizer clutching teeth for the following conditions:
    11. • Scuffs
    • Nicks
    • Burrs
    • Damage

    Object Number: 38591 Size: SH
  11. Measure the cap between the vertical faces of the blocking ring teeth and the synchronizer clutch gear as follows:
    12. 11.1. Assemble the correct blocking ring with the correct speed gear.
    11.2. The blocking ring must be fully seated on the gear.
    11.3. If dual cone, install both cones. Ensure the top edge of the friction cone is parallel to the gear face.
    11.4. Use a feeler gauge to measure the gear gap.
       • 1st gear 1.45-2.38 mm (0.057-0.094 in)
       • 2nd gear 1.42-2.40 mm (0.055-0.094 in)
       • Reverse, 3rd, 4th, and 5th gear 1.44-2.12 mm (0.057-0.083 in)
  12. Inspect the mainshaft drive gear clutching cones for synchronizer ring metal transfer.
  13. Inspect all the gear teeth for excess wear.
  14. Remove nicks and burrs with a soft stone or a crocus cloth.
  15. Replace any components that are bent or show signs of excessive wear. Inspect the mating parts.
  16. Inspect the bearings and the bearing surfaces for the following conditions:
    17. • Nicks
    • Burrs
    • Bent cages
    • Wear
    • Overheating
    • Scoring
    • Pitted condition

Synchronizer Assembly

    Object Number: 4732 Size: SH

    Important: Do not mix the parts for the synchronizers.

  1. Install the synchronizer detent balls, springs and keys to the hub.

    2. Object Number: 4810 Size: SH
  2. Align the scribe marks on the synchronizer hubs and sleeves.
  3. Install the synchronizer rings to the synchronizer hubs.