Synchros - All

Complete disassembly, inspection, and reassembly of the Borg-Warner T-56 6-speed manual transmission to replace all synchronizer assemblies, requiring transmission removal and internal rebuild.

Warnings

Tools required

Parts

• 1st-2nd synchronizer assembly × 1 — Use OEM specification
• 3rd-4th synchronizer assembly × 1 — Use OEM specification
• 5th-6th synchronizer assembly × 1 — Use OEM specification
• Reverse synchronizer assembly × 1 — Use OEM specification
• Transmission gasket and seal kit × 1 — Use OEM specification
• Transmission drain plug washer × 1 — Use OEM specification
• Transmission fill plug washer × 1 — Use OEM specification
• Clutch disc × 1 — Recommended replacement during access
• Pilot bearing × 1 — Recommended replacement during access

Fluids

• Mopar MS-9224 or 75W-90 GL-4 — 4.2 qt

Preparation

1. Park vehicle on level surface and engage parking brake.
2. Disconnect negative battery cable to prevent starter engagement.
3. Raise vehicle and support securely on jack stands under frame rails.
4. Remove rear wheels to access exhaust hangers if needed for clearance.
5. Allow exhaust system to cool completely if vehicle was recently driven.
6. Place drain pan under transmission and remove drain plug to drain gear oil completely.
7. Gather all parts, tools, and create organized workspace for small transmission components.
8. Have transmission rebuild manual or exploded diagram available for reference during disassembly.

Procedure

1. 1

   Remove exhaust system and driveshaft
   Disconnect exhaust system from manifold flanges and remove or support exhaust out of the way. Mark driveshaft-to-differential flange orientation with paint or punch marks. Remove the 4 driveshaft flange bolts and carefully lower driveshaft, supporting the front end to prevent damage to slip yoke. Plug transmission tailshaft housing with clean rag to prevent fluid leakage and contamination.
2. 2

   Disconnect shift linkage and electrical connections
   Remove shift knob by turning counterclockwise. Remove shift boot and console trim to access shifter mechanism. Disconnect shift linkage at transmission by removing the shift lever pivot bolt. Disconnect reverse light switch electrical connector at transmission. Disconnect vehicle speed sensor connector if equipped. Label all connections for reinstallation.
3. 3

   Support engine and remove transmission crossmember
   Position floor jack with wood block under engine oil pan to support engine weight. Remove the transmission crossmember mounting bolts from frame rails (2 per side). Remove transmission mount-to-crossmember fasteners. Carefully lower and remove crossmember from vehicle. Ensure engine is stable on jack before proceeding.
4. 4

   Remove transmission from vehicle
   Position transmission jack under transmission with adapter or secure cradle. Remove the bellhousing-to-engine block mounting bolts. Carefully slide transmission rearward on jack, ensuring input shaft clears clutch disc and pilot bearing. Angle transmission as needed to clear tunnel and components. Lower transmission from vehicle and move to clean workbench. Do not allow transmission weight to hang on input shaft.
   Torque spec

   Mounting Bolts61 Nm (45 lb-ft)
5. 5

   Remove bellhousing and external components
   Remove clutch release bearing and fork from bellhousing. Remove bellhousing mounting bolts from transmission case and separate bellhousing. Remove shift lever housing assembly from top of transmission case. Remove backup light switch and vehicle speed sensor if equipped. Remove fill plug and inspect for metal contamination on magnet. Remove transmission rear extension housing bolts and carefully separate extension housing from case, tapping gently with soft-face hammer if needed.
   Torque spec

   Sensor Bolts11 Nm (8 lb-ft)

   Fill Plug34 Nm (25 lb-ft)
6. 6

   Disassemble transmission case halves
   With transmission on bench, remove the bolts securing the rear extension housing and any side cover to the main case, following the T-56 factory disassembly sequence (the T-56 uses a one-piece main case with a removable rear extension housing, not split case halves). Note bolt locations as lengths may vary. Carefully separate case halves by tapping with soft-face hammer at designated pry points. Access the internal gear train and shift rail assemblies by removing the extension housing and sliding the shaft assemblies from the case per the T-56 factory procedure (the case does not separate into halves). Inspect case gasket surfaces and clean any old gasket material. Keep all snap rings, shims, and small parts organized by location.
7. 7

   Remove shift rail assemblies and shift forks
   Remove shift rail detent plugs, springs, and balls from case, keeping track of their positions. Carefully slide shift rails out of case, noting the order and orientation of each rail. Remove shift forks from synchronizer sleeves as rails are withdrawn. Inspect shift fork pads for wear and shift rail detent notches for damage. Label each fork and rail assembly to maintain correct positioning during reassembly.
8. 8

   Remove output shaft assembly
   Remove output shaft rear bearing snap ring from extension housing bore. Carefully lift output shaft assembly from case, keeping all gears, spacers, and synchronizer assemblies in order on the shaft. Place output shaft in padded vise or shaft holder. Note position and orientation of all gears and synchronizers before disassembly. Photograph assembly if needed for reference.
9. 9

   Disassemble output shaft and remove synchronizers
   Remove output shaft front bearing snap ring. Remove 5th-6th synchronizer snap ring and slide 5th-6th synchronizer assembly, 5th gear, and thrust washer from shaft. Remove snap ring retaining 3rd-4th synchronizer assembly and slide assembly off shaft along with 3rd and 4th gears. Remove 1st-2nd synchronizer snap ring and remove synchronizer assembly with 1st and 2nd gears. Keep all blocking rings, springs, and keys with their respective synchronizer assemblies. Inspect all gear teeth and bearing surfaces for wear or damage.
10. 10

    Remove input shaft and countershaft assemblies
    Remove input shaft front bearing retainer bolts and retainer. Remove input shaft snap ring and carefully remove input shaft from case, using soft hammer if needed. Remove countershaft rear bearing snap ring. Remove countershaft front bearing retainer and carefully extract countershaft assembly from case. Remove reverse idler shaft bolt and slide reverse idler shaft from case, removing reverse idler gear. Inspect all bearing surfaces and shaft splines for wear.
11. 11

    Remove reverse synchronizer assembly
    Locate reverse synchronizer assembly on countershaft or as separate assembly depending on T-56 variant. Remove snap ring securing reverse synchronizer. Slide reverse synchronizer assembly from shaft, noting orientation and position of blocking ring. Inspect reverse gear engagement teeth and synchronizer cone surface for wear. Set aside with other synchronizer assemblies for replacement.
12. 12

    Clean and inspect all components
    Thoroughly clean all shafts, gears, case halves, and bearings with parts cleaning solvent. Dry with compressed air and lint-free rags. Inspect all gear teeth for chips, cracks, or excessive wear. Check all bearing races and rollers for pitting or scoring. Inspect case bores and bearing pockets for damage. Measure shaft runout with dial indicator if available. Replace any worn or damaged components beyond synchronizers. Inspect blocking ring-to-gear cone clearance on all gears to ensure proper engagement surface condition.
13. 13

    Install new synchronizer assemblies on output shaft
    Begin output shaft reassembly with cleaned or new bearings and gears. Install 1st-2nd gear synchronizer assembly with new synchronizer in correct orientation, ensuring blocking rings seat properly on gear cones. Install snap ring to secure assembly. Install 3rd-4th gear synchronizer assembly with proper spacing and install retaining snap ring. Install 5th gear with thrust washer, then install new 5th-6th synchronizer assembly and secure with snap ring. Verify all snap rings are fully seated in grooves and synchronizer sleeves move freely. Check endplay on all gear positions with feeler gauge if specifications are available.
14. 14

    Install reverse synchronizer and reassemble countershaft
    Install new reverse synchronizer assembly on countershaft or in designated position, ensuring correct orientation of blocking ring. Install snap ring to secure assembly. Verify reverse synchronizer sleeve operation is smooth. Reinstall countershaft assembly into case with bearings properly seated. Install countershaft front bearing retainer and rear bearing snap ring. Install reverse idler gear and shaft, securing with bolt to specified torque.
15. 15

    Reinstall input shaft and output shaft assemblies
    Install input shaft into case with front bearing and snap ring, ensuring bearing is fully seated in bore. Install bearing retainer with new gasket if applicable. Carefully lower output shaft assembly into case, aligning all gears with countershaft gears. Ensure rear bearing seats fully in case bore. Install output shaft rear bearing snap ring in extension housing. Verify all shafts rotate freely and gears mesh properly without binding.
16. 16

    Install shift forks and shift rails
    Install shift forks onto respective synchronizer sleeves in correct positions as labeled during disassembly. Slide shift rails through case bores and shift forks, aligning detent notches. Install detent balls, springs, and plugs in correct locations, ensuring proper detent engagement. Verify each shift rail moves through full travel and detent action is positive. Check that all gears can be selected without interference.
17. 17

    Reassemble transmission case halves
    Apply thin bead of appropriate gasket sealer to case mating surface or install new case gasket per manufacturer specification. Reinstall the shaft assemblies into the one-piece case and refit the extension housing/side cover, ensuring all shift rails and components align properly (the T-56 case does not separate into halves). Install all case bolts in correct locations and tighten in criss-cross pattern to ensure even case seating. Verify case halves mate flush with no gaps. Rotate input and output shafts to verify smooth operation after case assembly.
18. 18

    Install extension housing and external components
    Install new extension housing gasket or apply sealer as specified. Install extension housing onto transmission case and tighten bolts in criss-cross pattern. Install shift lever housing with new gasket and tighten bolts. Install vehicle speed sensor and backup light switch with new seals, torqueing sensor bolts properly. Install bellhousing with new gasket and tighten mounting bolts. Install clutch release bearing and fork mechanism.
    Torque spec

    Sensor Bolts11 Nm (8 lb-ft)
19. 19

    Install transmission into vehicle
    Apply small amount of high-temperature grease to input shaft splines and pilot bearing surface. Position transmission on transmission jack and carefully raise into position. Align input shaft with clutch disc and pilot bearing, rotating output shaft as needed to align splines. Slide transmission forward until bellhousing contacts engine block evenly. Install bellhousing-to-engine mounting bolts and torque to specification. Do not use bolts to draw misaligned transmission into place.
    Torque spec

    Mounting Bolts61 Nm (45 lb-ft)
20. 20

    Reinstall crossmember, driveshaft, and linkages
    Raise transmission mount to crossmember and install fasteners. Position crossmember to frame rails and install mounting bolts, torqueing to specification. Remove engine support jack. Align driveshaft to differential flange using alignment marks and install flange bolts. Reconnect shift linkage at transmission shift lever location and secure with pivot bolt. Reconnect all electrical connectors including reverse light switch and vehicle speed sensor. Reinstall exhaust system or hangers as removed.
21. 21

    Fill transmission with gear oil
    Install drain plug with new washer and torque to specification. Using fluid pump or syringe, add the factory-specified transmission fluid (verify exact Chrysler/Mopar specification for the Viper T-56 — the T-56 typically requires a synthetic ATF-type fluid, NOT GL-4 gear oil) through fill plug opening until oil reaches bottom of fill plug hole. Install fill plug with new washer and torque to specification. Wipe away any spilled oil from transmission case.
    Torque spec

    Drain Plug34 Nm (25 lb-ft)

    Fill Plug34 Nm (25 lb-ft)
22. 22

    Final assembly and fluid check
    Reinstall shift boot, console trim, and shift knob. Reconnect negative battery cable. Lower vehicle from jack stands. Start engine and verify proper clutch operation. With engine off, verify all gears engage smoothly without grinding or excessive effort. Check under vehicle for any fluid leaks at drain plug, fill plug, extension housing, and case seams. Recheck fluid level after short test drive and top off if needed.

Reassembly

1. Ensure all snap rings are fully seated in their grooves and all synchronizer assemblies move freely before case reassembly.
2. Apply transmission assembly lubricant to all bearings and thrust surfaces during reassembly to prevent initial startup wear.
3. Verify gear mesh and shaft rotation smoothness at each stage of assembly before proceeding to next step.
4. Use new gaskets and seals throughout reassembly; do not reuse old gaskets.
5. Torque all fasteners in criss-cross pattern to prevent warping of case halves and covers.
6. Double-check shift rail detent ball and spring installation to prevent incomplete gear engagement.
7. When installing transmission into vehicle, never force transmission forward with bolts; input shaft must align freely with clutch disc.

Verification

• With vehicle raised and engine off, manually shift through all gears and verify smooth engagement without grinding or resistance.
• Start engine and verify clutch disengages completely, allowing smooth gear selection.
• Perform test drive through all gears, verifying smooth shifts under light and moderate load without synchro clash.
• Check for unusual noises in neutral, each gear, and during shifts that would indicate improper assembly or inadequate lubrication.
• Verify reverse light operation when reverse gear is selected.
• After test drive, recheck transmission fluid level and inspect for leaks at all sealing surfaces.
• Verify shift linkage adjustment provides full gear engagement and proper shift gate feel.

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