Synchros - All

Complete removal, inspection, and replacement of all synchronizers in the Tremec T-56 6-speed manual transmission of a 2008 Dodge Viper, requiring transmission removal and full disassembly.

Warnings

Tools required

Parts

• 1st-2nd gear synchronizer assembly × 1 — Use OEM Tremec specification
• 3rd-4th gear synchronizer assembly × 1 — Use OEM Tremec specification
• 5th-6th gear synchronizer assembly × 1 — Use OEM Tremec specification
• Reverse synchronizer assembly × 1 — Use OEM Tremec specification
• Transmission case gasket × 1 — Use OEM specification
• Extension housing gasket × 1 — Use OEM specification
• Front bearing retainer seal × 1 — Use OEM specification
• Rear output shaft seal × 1 — Use OEM specification
• Shift rail O-rings × 1 — Use OEM specification
• Transmission assembly lube × 1 — Use OEM specification

Fluids

• Pennzoil Synchromesh 75W-90 — 4.2 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Disconnect negative battery cable
3. Raise vehicle on lift or jack stands to working height with adequate clearance for transmission removal
4. Remove exhaust system from manifolds rearward to provide clearance
5. Drain transmission fluid into appropriate container
6. Remove driveshaft and mark yoke-to-flange orientation for reinstallation
7. Disconnect shift linkage at transmission
8. Disconnect hydraulic clutch line at transmission using flare wrench
9. Disconnect backup light switch connector and speed sensor connector
10. Install engine support fixture or secure engine with hoist to support weight after transmission removal
11. Prepare clean workbench or transmission stand for disassembly

Procedure

1. 1

   Remove transmission from vehicle
   Position transmission jack under transmission and secure with safety chain. Remove bellhousing-to-engine bolts. Verify the exact bolt count against factory service documentation before removal. Support transmission weight and carefully slide transmission rearward off input shaft and clutch splines. Lower transmission from vehicle and transport to clean work area. Mount transmission on stand if available.
2. 2

   Remove external components
   Remove clutch release bearing and fork from bellhousing. Remove bellhousing from transmission case by removing the mounting bolts. Remove backup light switch and vehicle speed sensor from case. Remove shift tower assembly by removing the mounting bolts and lifting away. Note position of detent springs and balls as tower is removed.
3. 3

   Separate transmission case halves
   Remove the case half bolts in a crisscross pattern working from outside to center. Verify the exact case-half bolt count against factory service documentation before removal. Carefully separate the rear case half from the front case using light taps with a dead blow hammer on bosses only. Never pry between sealing surfaces. Lift rear case away exposing the gear train and shift rail assembly.
4. 4

   Remove extension housing and output shaft
   Remove extension housing bolts and slide housing off output shaft. Remove output shaft rear bearing snap ring using snap ring pliers. Note orientation of bearing for reinstallation. With rear case removed, the output shaft assembly can now be lifted from the front case. Support the shaft and carefully lift straight up to clear all gears and synchronizers.
5. 5

   Remove input shaft and 3rd-4th synchronizer
   Remove input shaft front bearing retainer bolts and slide retainer forward off input shaft. Remove input shaft front bearing snap ring. The input shaft and 3rd-4th gear synchronizer assembly can now be removed as a unit from the front case. Use caution as the 3rd-4th synchronizer hub is press-fit onto the input shaft.
6. 6

   Disassemble and remove 5th-6th synchronizer
   The 5th-6th synchronizer is located at the rear of the output shaft. Remove the large snap ring retaining the synchronizer assembly. Slide the 6th speed gear, synchronizer ring, synchronizer sleeve, and hub assembly off the shaft. Mark the hub and sleeve orientation before separating. Remove the 5th speed gear and its synchronizer ring. Inspect all components for wear, scoring, or heat discoloration.
7. 7

   Disassemble and remove 3rd-4th synchronizer
   With input shaft removed, the 3rd-4th synchronizer assembly is accessible. Remove the snap ring retaining the synchronizer hub to the input shaft. The hub is press-fit and will require a press to remove. Mark the hub and sleeve position before disassembly. Separate the synchronizer sleeve from hub, noting position of spring and inserts. Remove synchronizer rings from both 3rd and 4th gears.
8. 8

   Disassemble and remove 1st-2nd synchronizer
   The 1st-2nd synchronizer is located mid-shaft on the output shaft. Remove the snap ring forward of the synchronizer hub. Slide the 2nd speed gear, synchronizer ring, synchronizer assembly, and 1st speed gear off the output shaft. Mark hub and sleeve orientation. The 1st-2nd synchronizer hub may be splined and keyed to the shaft. Note orientation of all components including thrust washers.
9. 9

   Remove reverse synchronizer assembly
   The reverse gear and synchronizer are located on the countershaft or as part of the shift rail mechanism depending on Tremec TR-6060 variant. Remove the reverse idler gear shaft retaining bolt. Slide the reverse idler shaft out and remove the reverse idler gear. Remove the reverse synchronizer assembly from its mounting position. Mark all components for reinstallation orientation.
10. 10

    Inspect all components and prepare for reassembly
    Thoroughly clean all parts in solvent and dry with compressed air. Inspect all gear teeth for chips, cracks, or excessive wear. Check all bearing surfaces for scoring or discoloration. Measure synchronizer ring-to-gear clearance with feeler gauges; compare against the factory wear-limit specification for the TR-6060. Check shift fork pad wear. Inspect all snap rings for distortion. Replace any questionable components. Lay out new synchronizer assemblies and confirm correct application for each position.
11. 11

    Install reverse synchronizer
    Lubricate reverse synchronizer assembly with transmission assembly lube. Install reverse synchronizer onto its mounting position in original orientation per disassembly marks. Install reverse idler gear onto shaft with lubricated bearings. Insert reverse idler shaft and install retaining bolt. Verify reverse idler gear rotates freely and has proper end play.
12. 12

    Install 1st-2nd synchronizer assembly
    Lubricate output shaft with assembly lube. Install 1st speed gear and synchronizer ring onto output shaft with ring groove facing synchronizer position. Assemble new 1st-2nd synchronizer hub and sleeve in marked orientation with new springs and inserts. Slide synchronizer assembly onto shaft in correct orientation. Install 2nd speed gear synchronizer ring with groove facing away from 1st gear. Install 2nd speed gear. Install retaining snap ring ensuring it is fully seated in groove.
13. 13

    Install 3rd-4th synchronizer assembly
    Press new 3rd-4th synchronizer hub onto input shaft in original orientation using shop press and appropriate mandrel. Ensure hub is pressed to correct depth and install retaining snap ring. Lubricate synchronizer rings with assembly lube and install on 3rd and 4th gears with grooves facing the synchronizer. Assemble synchronizer sleeve onto hub in marked orientation with new springs and inserts. Check synchronizer operation by sliding sleeve; it should move smoothly with spring tension.
14. 14

    Install 5th-6th synchronizer assembly
    Install 5th speed gear onto output shaft with synchronizer ring and groove facing rearward. Lubricate assembly lube on all components. Assemble new 5th-6th synchronizer hub and sleeve with springs and inserts in correct orientation. Slide assembly onto output shaft. Install 6th speed gear and synchronizer ring. Install large retaining snap ring ensuring complete seating in groove. Check end play and synchronizer movement.
15. 15

    Reassemble transmission case
    Apply thin bead of RTV silicone to front case sealing surface per factory pattern. Install input shaft assembly into front case with front bearing. Install output shaft assembly into front case, carefully aligning all gears and ensuring shift forks engage synchronizer sleeves correctly. Install shift rail assemblies ensuring detent balls and springs are in position. Carefully lower rear case half onto front case, ensuring case dowel pins align. Install case bolts and tighten in crisscross pattern working from center outward.
16. 16

    Install extension housing and external components
    Install new rear output shaft seal into extension housing. Slide extension housing onto output shaft with new gasket. Install and tighten housing bolts. Install new front bearing retainer seal. Install bearing retainer with new gasket. Install shift tower assembly with new gasket, ensuring detent springs and balls are positioned correctly. Install backup light switch and speed sensor with new O-rings. Install bellhousing with new gasket.
17. 17

    Reinstall transmission in vehicle
    Apply small amount of high-temperature grease to input shaft splines. Use clutch alignment tool to verify clutch disc alignment. Raise transmission into position using transmission jack. Carefully align input shaft with clutch disc splines and pilot bearing. Slide transmission forward onto engine, ensuring bellhousing mates flush with engine block. Install bellhousing-to-engine bolts and tighten in star pattern. Remove transmission jack. Connect hydraulic clutch line using new crush washer if equipped. Connect shift linkage and adjust per factory specification. Connect backup light switch and speed sensor connectors. Install driveshaft in original orientation. Install exhaust system with new gaskets as needed.
18. 18

    Fill transmission and perform initial checks
    Fill transmission with the factory-specified manual transmission fluid and capacity per the 2008 Viper service manual through the fill plug opening. Fluid should reach bottom of fill plug hole. Install fill plug. Remove engine support fixture. Reconnect negative battery cable. Start engine and depress clutch pedal. Check for leaks at all connections, case seams, and seals. With engine running and clutch depressed, shift through all gears checking for smooth engagement. Check clutch pedal feel and travel.

Reassembly

1. All synchronizer assemblies must be installed in their original orientations as marked during disassembly
2. Use only the specified Pennzoil Synchromesh 75W-90 transmission fluid; other fluids will cause shifting problems and synchronizer wear
3. All snap rings must be fully seated in their grooves; partial seating will cause catastrophic failure
4. Torque all fasteners to specification when values become available in database
5. Apply RTV silicone only to case sealing surfaces; excess sealant can block oil passages
6. Driveshaft must be reinstalled in original orientation to maintain balance

Verification

• Start engine and verify no fluid leaks from transmission case, extension housing, or hydraulic clutch connection
• With engine running and clutch depressed, shift through all gears verifying smooth engagement without grinding or resistance
• Test drive vehicle through all gears under light load; all shifts should be smooth and positive with no gear clash
• Verify reverse gear engages cleanly without grinding
• Check for proper clutch pedal feel and complete disengagement; adjust linkage if necessary
• After test drive, recheck fluid level and inspect for leaks with transmission at operating temperature
• Verify no abnormal noises from transmission in any gear or during shifts

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