Synchros - All

Complete rebuild of the manual transmission synchronizer assemblies for all forward gears, including transmission removal, disassembly, synchronizer replacement, and reinstallation.

Warnings

Tools required

Parts

• 1st-2nd gear synchronizer assembly × 1 — Use OEM specification
• 3rd-4th gear synchronizer assembly × 1 — Use OEM specification
• Reverse idler gear (if equipped with synchro) × 1 — Use OEM specification
• Transmission gasket and seal kit × 1 — Use OEM specification
• Input shaft bearing retainer seal × 1 — Use OEM specification
• Countershaft bearing set × 1 — Use OEM specification
• Main shaft bearing × 1 — Use OEM specification
• Pilot bearing or bushing × 1 — Use OEM specification
• Clutch release bearing × 1 — Use OEM specification
• Rear transmission mount × 1 — Use OEM specification if damaged
• Manual transmission fluid (gear oil) × 1 — 80W-90 GL-4 rated

Fluids

• 80W-90 GL-4 manual transmission fluid — 3.5 qt

Preparation

1. Park vehicle on level ground and set parking brake firmly
2. Disconnect negative battery cable to prevent starter engagement
3. Drain transmission fluid into appropriate container while warm for easier flow
4. Remove driveshaft: mark pinion flange and driveshaft yoke for reinstallation alignment, remove 4 U-joint strap bolts, slide driveshaft rearward to disengage from transmission
5. Disconnect speedometer cable from transmission tailhousing
6. Disconnect shift linkage at transmission (varies by column vs floor shift configuration)
7. Support engine with floor jack and wood block under oil pan to prevent engine sag
8. Remove transmission crossmember mounting bolts and lower crossmember away from transmission
9. Disconnect clutch linkage at bellhousing or clutch fork
10. Remove bellhousing inspection cover if equipped

Procedure

1. 1

   Remove transmission from vehicle
   Position transmission jack under transmission pan and secure with transmission jack strap or chain. Remove the bellhousing-to-engine block bolts (typically 6 bolts — verify count for your specific bellhousing). Carefully slide transmission rearward on input shaft until input shaft clears clutch disc and pilot bearing. Maintain level orientation to avoid binding. Lower transmission slowly and remove from under vehicle. Place on clean workbench.
2. 2

   Remove bellhousing and external components
   Remove the bolts securing bellhousing to transmission case (verify exact count for your specific transmission). Separate bellhousing from transmission. Remove clutch release bearing and fork assembly. Remove shift cover assembly: remove the 7 bolts securing top shift cover, lift cover and shifter mechanism away as an assembly. Inspect shift forks for wear; replace if grooves deeper than 0.030 inch are present. Verified detail (Ford manual transmissions of this era typically use 4-6 bolts to secure the bellhousing to the case, but the exact count varies by transmission type (3-speed vs 4-speed). The 3-speed typically uses 4 bolts, but the 4-speed may use more. This should be verified for accuracy.): Remove the bolts securing bellhousing to transmission case (typically 4 bolts on 3-speed, verify count for your specific transmission).
3. 3

   Remove extension housing and output components
   Remove the bolts securing tailhousing/extension housing to transmission case (verify exact count for your transmission). Tap housing with soft hammer to break gasket seal and slide rearward off output shaft. Remove speedometer drive gear snap ring and slide gear off output shaft. Remove output shaft rear bearing snap ring from inside extension housing bore.
4. 4

   Remove input shaft and bearing retainer
   Remove the 4 bolts securing front bearing retainer to transmission case. Carefully tap retainer with soft hammer to break gasket seal. Pull input shaft and bearing retainer assembly forward and out of case. The input shaft bearing will remain pressed onto input shaft. Inspect input shaft gear teeth and bearing surface for scoring or pitting.
5. 5

   Remove countershaft and cluster gear
   Using a brass drift punch slightly smaller than countershaft diameter, drive countershaft rearward and out of case from front to rear. Have drain pan ready as needle bearings may fall. Lower cluster gear carefully into bottom of case. Remove cluster gear and collect all needle bearing rollers (count varies by transmission — verify exact number per end against the factory service manual). Inspect cluster gear teeth for chipping or excessive wear.
6. 6

   Remove output shaft assembly
   Tilt transmission case to access output shaft from rear. Carefully work output shaft assembly rearward and out of case. The entire gear train (1st, 2nd, 3rd gears and both synchronizer assemblies) will come out as a unit on the output shaft. Place assembly on clean bench. Note orientation and order of all components for reassembly reference.
7. 7

   Disassemble output shaft - remove 3rd-4th synchronizer
   For 4-speed: Remove snap ring securing 3rd-4th synchronizer hub to output shaft. Using snap ring pliers, remove synchronizer hub retaining snap ring. Slide 3rd-4th synchronizer assembly, blocking ring, and 3rd gear off shaft. Keep synchronizer springs, keys (inserts), and hub together as an assembly. Inspect 3rd gear and its blocking ring cone surface for scoring. For 3-speed: The front synchronizer is 2nd-3rd; procedure is similar.
8. 8

   Disassemble output shaft - remove 1st-2nd synchronizer
   Remove snap ring ahead of 2nd gear. Slide 2nd gear, blocking ring, and 1st-2nd synchronizer assembly off shaft. Remove 1st gear thrust washer and 1st gear. Collect all blocking rings and label them by gear position. Inspect all gear cone surfaces and blocking ring inner cones for scoring, heat discoloration, or wear. Check synchronizer sleeve teeth for rounded edges or excessive wear.
9. 9

   Inspect and measure synchronizer components
   Disassemble each synchronizer: note position of springs and keys (typically 3 keys per hub, offset springs). Measure clearance between blocking ring and gear cone using feeler gauge; a new blocking ring typically shows approximately 0.030-0.050 inch clearance. Replace any ring whose clearance has worn below the service limit (verify exact spec in factory service manual). Check synchronizer sleeve-to-hub engagement teeth for wear. Inspect all blocking ring teeth for chips or rounded edges. Replace any blocking ring worn below the factory service wear limit or showing visible damage (verify exact clearance spec in factory service manual).
10. 10

    Clean and inspect transmission case and shafts
    Thoroughly clean transmission case interior with solvent and compressed air. Inspect case for cracks, especially around bearing bores and bolt holes. Measure output shaft journal diameters at bearing and gear mounting surfaces; compare to factory service manual specifications for your specific transmission. Check for scoring or wear exceeding 0.001 inch. Inspect shift fork shaft bores for elongation or wear.
11. 11

    Assemble new synchronizers onto output shaft
    Install 1st gear onto output shaft with cone facing forward. Install new 1st gear blocking ring onto gear cone. Assemble new 1st-2nd synchronizer: install 3 keys into hub slots, position springs on opposite sides offset by one key position. Slide synchronizer assembly onto shaft with shift fork groove facing 1st gear. Install 2nd gear blocking ring, then 2nd gear with cone facing rearward. Secure with snap ring ensuring it seats fully in groove.
12. 12

    Install 3rd-4th synchronizer assembly
    For 4-speed: Install 3rd gear with cone facing forward. Install new 3rd gear blocking ring. Assemble new 3rd-4th synchronizer using same key and spring orientation as 1st-2nd. Slide assembly onto output shaft with shift fork groove facing forward. Install retaining snap ring ensuring full engagement in shaft groove. Check all gears for free rotation and proper blocking ring engagement. For 3-speed: Install 2nd-3rd synchronizer in similar fashion.
13. 13

    Install output shaft assembly into case
    Tilt transmission case at approximately 45 degrees. Carefully guide output shaft assembly into case from rear, ensuring blocking rings remain aligned with synchronizer hubs. Rotate shaft as needed to mesh gears with their proper positions. Seat output shaft front bearing into its bore in case. Do not force; tap gently with soft hammer if needed.
14. 14

    Install cluster gear and countershaft
    Coat all needle bearing surfaces with assembly lube or heavy grease. Install 22 needle bearings into each end of cluster gear bore using grease to hold them in place. Install thrust washers at each end of cluster gear (tabs must engage case slots). Position cluster gear in bottom of case. Insert countershaft dummy shaft (or actual countershaft) from rear to hold bearings in place. Align cluster gear with countershaft bore holes in case front and rear.
15. 15

    Install input shaft and front bearing retainer
    Coat input shaft pilot bearing surface with light grease. Guide input shaft into case, meshing input shaft gear with cluster gear. Align input shaft bearing with front case bore and seat fully. Position new gasket on case. Install front bearing retainer with oil return slot at bottom (6 o'clock position). Install the retainer bolts finger tight, then torque in crossing pattern (verify exact bolt count for your transmission). Install new input shaft seal into bearing retainer if not already installed.
16. 16

    Install reverse idler gear and complete internal assembly
    Install reverse idler gear onto its shaft (if removed). Ensure reverse idler shaft retaining bolt or pin is properly secured. Drive countershaft fully into position from rear, pushing dummy shaft (if used) out the front. Ensure countershaft retaining pin or bolt hole aligns properly. Install countershaft retaining hardware. Check that all gears rotate freely and mesh properly by hand-rotating input shaft.
17. 17

    Install extension housing
    Install new output shaft rear bearing if removed (press onto shaft using bearing driver). Install output shaft bearing retaining snap ring inside extension housing bore. Apply new gasket or RTV gasket maker to extension housing mating surface. Slide extension housing over output shaft and onto case, ensuring speedometer drive gear slot aligns properly. Install the 6 extension housing bolts and torque in star pattern.
18. 18

    Install shift mechanism and covers
    Position shift forks into their respective synchronizer sleeve grooves (verify correct fork to gear assignment). Install shift rail through case and forks, ensuring detent notches align properly. Install detent springs and balls into case bores; secure with plugs. Apply new gasket to shift cover. Position shift cover assembly onto case, aligning shift forks with cover mechanism. Install the 7 shift cover bolts and torque in crossing pattern. Test shift mechanism operation through all gears before final installation.
19. 19

    Install bellhousing and prepare for installation
    Install new clutch release bearing onto fork. Position fork into bellhousing pivot. Install new bellhousing gasket. Mount bellhousing to transmission case using the 4 mounting bolts; torque in crossing pattern. Verify clutch fork operates smoothly. Apply light coat of high-temp grease to input shaft splines and pilot bearing surface. Inspect pilot bearing in crankshaft; replace if rough or worn.
20. 20

    Install transmission into vehicle
    Apply thin coat of clutch alignment tool grease to input shaft splines. Position transmission on transmission jack and raise into position. Align input shaft with clutch disc splines (clutch disc must be properly aligned using clutch alignment tool if clutch was serviced). Carefully guide input shaft through clutch disc and into pilot bearing. Slide transmission forward until bellhousing contacts engine block. Install the bellhousing-to-engine bolts (typically 6) and torque in crossing pattern.
21. 21

    Reconnect drivetrain and fill transmission
    Raise transmission slightly and install transmission crossmember. Install crossmember mounting bolts. Reconnect shift linkage at transmission and adjust per factory specifications (column shift requires specific adjustment procedure). Align driveshaft-to-pinion flange marks made during disassembly. Install U-joint strap bolts and torque. Reconnect speedometer cable. Reconnect clutch linkage and adjust free play to 7/8 to 1-1/8 inch at pedal pad per factory specifications. Fill transmission with GL-4 rated 80W-90 gear oil through fill plug until oil reaches bottom of fill plug hole (approximately 3.5 pints for the 3-speed; verify capacity for your specific transmission).

Reassembly

1. Reconnect negative battery cable after all mechanical work is complete
2. Check transmission fluid level after initial test drive and top off if needed
3. Inspect shift linkage adjustment after first test drive and readjust if needed
4. Check all transmission mounting bolts for proper torque after 50 miles of operation

Verification

• Start engine and verify clutch disengages fully without grinding when shifting into 1st gear from neutral
• Test drive vehicle and verify smooth shifts into all gears without grinding, balking, or jump-out
• Verify no gear whine or unusual noises in any gear under load and deceleration
• Check for transmission fluid leaks at all gasket surfaces and seals after test drive
• Verify proper shift linkage operation: all gears should engage positively without excessive force
• Confirm no vibration from driveline (indicates proper driveshaft alignment)
• Test synchronizer operation: all upshifts and downshifts should be smooth without double-clutching required

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