Replace a single worn or damaged synchronizer assembly in the manual transmission by disassembling the transmission, separating the case halves, and replacing the failed synchro on the affected gear.

Warnings

Tools required

Parts

• Synchronizer assembly (specific to failed gear) × 1 — Use OEM specification or Borg-Warner T10 equivalent
• Transmission case gasket × 1 — Use OEM specification
• Transmission side cover gasket × 1 — Use OEM specification
• Transmission input shaft bearing retainer gasket × 1 — Use OEM specification
• Transmission rear seal × 1 — Use OEM specification
• Shift fork pads (if worn) × 1 — Use OEM specification
• Gasket sealer (Permatex Aviation Form-A-Gasket) × 1 — Permatex 80019
• Thread locker (blue, medium-strength) × 1 — Loctite 243

Fluids

• 75W-90 GL-5 Gear Oil — 3.5 qt

Preparation

1. Identify which gear has the failed synchronizer through test driving or disassembly inspection notes
2. Raise vehicle and secure on four jack stands positioned under frame rails
3. Disconnect negative battery cable
4. Remove exhaust system from manifolds back to permit transmission removal clearance
5. Remove driveshaft: mark rear yoke to differential flange relationship, remove 4 U-joint bolts, slide driveshaft rearward to clear transmission output shaft
6. Disconnect speedometer cable from transmission
7. Disconnect shift linkage at transmission side cover
8. Support transmission with transmission jack centered under transmission case
9. Remove transmission mount-to-crossmember fasteners
10. Remove crossmember-to-frame fasteners and remove crossmember

Procedure

1. 1

   Remove transmission from vehicle
   Remove the 4 bell housing bolts securing transmission to engine. Slide transmission rearward on transmission jack until input shaft clears clutch assembly. Carefully lower transmission and remove from under vehicle. Clean exterior of transmission case thoroughly before disassembly to prevent contamination of internal components.
2. 2

   Drain transmission fluid
   Position transmission on work bench with drain plug accessible. Remove drain plug from bottom of transmission case and drain fluid completely into drain pan. Inspect drained fluid for metal particles or debris that may indicate additional wear. Reinstall drain plug hand-tight for now.
3. 3

   Remove transmission side cover
   Remove the 8 side cover bolts. Carefully lift side cover away from case, noting positions of all detent balls, springs, and shift forks. There are 3 detent assemblies (one per shift rail) that must be documented. Place detent components in organized containers to prevent loss or mixing.
4. 4

   Remove input shaft bearing retainer
   Remove the 4 bolts securing the front bearing retainer to the transmission case. Pull bearing retainer forward off input shaft. Remove and discard the gasket. Inspect input shaft bearing for roughness or damage.
5. 5

   Separate transmission case halves
   Remove the 11 bolts securing the main case to the extension housing. Use a rubber mallet to tap gently around the case perimeter to break the gasket seal. Carefully separate the case halves, keeping the gear train assembly with the main case. Remove and discard the case gasket.
6. 6

   Remove countershaft and cluster gear
   Using a brass drift, drive the countershaft rearward out of the case. The cluster gear will drop to the bottom of the case. Carefully lift cluster gear out, keeping the roller bearings and thrust washers with the gear. Count and document all roller bearings (typically 28 per end, 56 total) for reassembly verification.
7. 7

   Remove output shaft assembly
   Tilt the output shaft assembly and maneuver it out of the main case. The entire mainshaft with all gears, synchronizers, and bearings will come out as one assembly. Place on clean workbench for further disassembly.
8. 8

   Disassemble output shaft to access failed synchronizer
   Remove the rear output shaft snap ring. Using snap ring pliers, remove snap rings securing gears and synchronizers on the mainshaft. Work from rear to front, removing: speedometer drive gear, rear bearing, reverse gear, 1st-2nd synchronizer assembly (if this is the failed unit), 1st gear, 2nd gear, 3rd-4th synchronizer assembly (if this is the failed unit), and 3rd gear. Note exact order and orientation of all components. Use transmission input shaft holder tool to secure shaft during snap ring removal.
9. 9

   Remove failed synchronizer assembly
   Once you reach the failed synchronizer, carefully remove the snap ring securing it to the mainshaft. Slide the synchronizer assembly off the shaft, noting the position of the shift fork groove. Disassemble the synchronizer by carefully removing the hub, sleeve, and 3 synchronizer keys with springs. Inspect the mating gear's cone surface for scoring or discoloration.
10. 10

    Inspect and clean all components
    Thoroughly clean all disassembled components with solvent. Inspect the gear cone surface, shift fork pads, mainshaft splines, and bearing surfaces for wear. Check synchronizer cone-to-gear clearance with feeler gauge; clearance should be 0.002 to 0.007 inches. Replace any worn components including shift fork if pad wear exceeds 0.020 inches depth.
11. 11

    Install new synchronizer assembly
    Install the new synchronizer hub onto the mainshaft with the shift fork groove facing the correct direction (match orientation of removed unit). Install the 3 synchronizer keys into the hub slots, then install the two springs 180 degrees apart with hooked ends engaging different keys. Slide the synchronizer sleeve over the hub, aligning key slots. Install the retaining snap ring, ensuring it seats fully in the mainshaft groove.
12. 12

    Reassemble output shaft
    Reassemble all gears and components onto the mainshaft in exact reverse order of disassembly. Install each snap ring and verify full seating in grooves. Check end play of each gear after snap ring installation; 1st and 2nd gear end play should be 0.004 to 0.018 inches, 3rd gear should be 0.003 to 0.014 inches. Install rear bearing and speedometer drive gear.
13. 13

    Reinstall output shaft into case
    Place the assembled output shaft into the main transmission case, carefully aligning all components. Ensure the shift forks will engage their respective synchronizer grooves when side cover is installed. Position input shaft into front of case, meshing with output shaft.
14. 14

    Install cluster gear and countershaft
    Coat cluster gear roller bearings with assembly lubricant. Install the 28 roller bearings into each end of cluster gear bore using heavy grease to hold them in place. Install thrust washers on each end. Position cluster gear in case bottom. Insert countershaft from rear of case, driving it forward through the cluster gear and case bore. Ensure countershaft is fully seated and cluster gear rotates freely.
15. 15

    Mate case halves and install side cover
    Apply thin bead of gasket sealer to case mating surface. Position new gasket on main case. Carefully align extension housing and install onto main case, guiding output shaft through rear bearing and seal. Install the 11 case bolts with thread locker and tighten in a cross-pattern to secure case halves. Install detent balls and springs in their documented positions. Apply gasket sealer and new gasket to side cover. Align shift forks with synchronizer grooves and install side cover with 8 bolts. Install input shaft bearing retainer with new gasket and 4 bolts.
16. 16

    Fill transmission and reinstall
    With transmission level, fill through side cover opening with approximately 2.5 pints (1.25 quarts) of GL-4 80W-90 gear oil until oil reaches bottom of fill hole. Install and tighten fill plug. Position transmission on transmission jack and raise into vehicle. Align input shaft with clutch disc splines and slide transmission forward into bell housing. Install 4 bell housing bolts. Reinstall crossmember, transmission mount, driveshaft (aligning marks), shift linkage, speedometer cable, and exhaust system.

Reassembly

1. Tighten all transmission case and cover bolts to proper specification using torque wrench in cross-pattern
2. Verify shift linkage adjustment after transmission installation to ensure proper gate engagement
3. Double-check driveshaft U-joint bolt torque and verify alignment marks are matched
4. Refill transmission to proper level after initial test drive and recheck for leaks

Verification

• Start engine with clutch pedal depressed and verify transmission shifts smoothly through all gears with engine running
• Test drive vehicle through all gears, confirming repaired synchronizer allows smooth engagement without grinding or balking
• Check for fluid leaks at case gasket, side cover, input shaft bearing retainer, and rear seal after test drive
• Verify no abnormal transmission noise in neutral or during gear engagement
• Confirm smooth shift action with no excessive effort required for the repaired gear

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