Synchros - Single Gear

This procedure covers removal, disassembly, and replacement of a single synchronizer assembly in the Aston Martin DB9 Touchtronic 6-speed automatic transmission, requiring full transmission removal and internal teardown.

Warnings

Tools required

Parts

• Synchronizer assembly (gear-specific) × 1 — Use OEM specification for specific gear
• Transmission drain plug crush washer × 1 — Use OEM specification
• Transmission case gasket/sealant × 1 — Use OEM anaerobic sealant
• Transmission output shaft seal × 1 — Use OEM specification
• Transmission input shaft seal × 1 — Use OEM specification
• Transmission mount bolts (if reuse not permitted) × 4 — Use OEM specification
• Propeller shaft coupling bolts × 6 — Use OEM specification
• Shift fork retaining clips (if damaged) × 2 — Use OEM specification

Fluids

• Touchtronic 6-speed ZF ATF — 9.5 qt

Preparation

1. Park vehicle on level ground and engage parking brake.
2. Disconnect negative battery terminal and wait 15 minutes for system capacitor discharge.
3. Raise vehicle on lift or support securely on jack stands at all four corners, ensuring sufficient working clearance underneath.
4. Remove transmission undertray panels using Torx fasteners.
5. Mark propeller shaft-to-differential flange orientation with paint pen for installation alignment.
6. Place drain pan under transmission and allow adequate cooling time if vehicle was recently operated.
7. Have transmission jack and support fixture positioned and ready before beginning removal.
8. Photograph all electrical connector orientations and routing for reference during reinstallation.

Procedure

1. 1

   Drain transmission fluid
   Position drain pan beneath transmission. Remove transmission drain plug from bottom of case using appropriate socket. Allow fluid to drain completely (approximately 20-30 minutes). Inspect drained fluid for metal particles or debris indicating additional internal damage. Install new crush washer on drain plug but do not reinstall plug yet.
   Torque spec

   Transmission Drain Plug30 Nm (22 lb-ft)
2. 2

   Disconnect propeller shaft
   NOTE: The DB9 uses a rear-mounted transaxle connected to the engine via a torque tube/propeller shaft. Verify the correct driveline disconnection points and coupling bolt count for this transaxle layout before proceeding. Support the torque-tube driveshaft assembly. Note that the DB9 uses a rear transaxle connected to the engine via a torque tube; follow the transaxle-specific removal sequence rather than a conventional front-gearbox procedure. Secure shaft to chassis with wire to prevent damage during transmission removal.
3. 3

   Disconnect electrical connections and shift actuators
   Disconnect transmission electrical connectors (reverse light switch, speed sensor) as fitted. Release wiring harness clips from transaxle case. If equipped, disconnect the clutch slave/concentric hydraulic line, capturing residual fluid in drain pan. Cap all open hydraulic ports immediately to prevent contamination. (Verify exact connector/actuator layout against factory documentation for the manual transaxle fitted.) Note: Disconnect transmission electrical connectors (reverse light switch, speed sensor). Release wiring harness clips from transmission case. Disconnect clutch slave cylinder hydraulic line and cap the open port to prevent contamination and fluid loss.
4. 4

   Remove transmission crossmember and mounts
   Support transmission securely with transmission jack. Remove transmission mount-to-crossmember fasteners using E-Torx sockets. Remove crossmember-to-chassis fasteners and lower crossmember away. Verify transmission is fully supported before proceeding.
5. 5

   Separate transmission from engine
   Disconnect the transaxle from the torque tube and remove the transaxle mounting fasteners per the DB9 rear-transaxle removal sequence. Verify the specific fastener count and type in OEM service data; the transaxle is not bolted to the engine block via a conventional front bellhousing. Lower transmission and position on clean workbench for disassembly. Note: Install bellhousing-to-engine fasteners and torque to OEM specification (verify exact torque from factory manual for this engine/transmission). Note: Separate transaxle from torque tube / driveline (verify correct disconnection procedure for the rear transaxle layout)
6. 6

   Remove external components and case fasteners
   With transmission on bench, remove clutch actuator assemblies, solenoid pack, speed sensors, and any external brackets. Clean case exterior thoroughly. Remove case halves fasteners in cross-pattern sequence (approximately 20-24 fasteners around case perimeter). Note fastener lengths as they vary by position.
7. 7

   Split transmission case
   Carefully separate case halves using plastic pry points only (never metal tools on mating surfaces). Use gentle tapping with plastic mallet if necessary. Lift upper case half vertically to expose internal components. Position case halves in secure fixture to prevent rolling.
8. 8

   Document and measure endplay
   Before disturbing any components, use dial indicator to measure shaft endplay and gear position. Record all measurements. Photograph shaft positions, shim locations, and snap ring orientations. Note position of any selective shims or thrust washers.
9. 9

   Remove shift forks and rails
   Remove shift fork retaining hardware using appropriate tools. Carefully slide shift rail out of case, noting detent ball and spring positions. Remove shift fork from engagement with synchronizer sleeve. Inspect fork pads for wear or scoring.
10. 10

    Remove gear cluster assemblies
    Remove snap rings securing gear clusters to shafts using internal snap ring pliers. Note snap ring orientation and thickness. Carefully slide gear assemblies off shafts, keeping all components in order. Use bearing puller if necessary to remove press-fit bearings. Identify the specific synchronizer assembly requiring replacement based on gear position.
11. 11

    Disassemble and replace synchronizer
    With target gear assembly removed, disassemble synchronizer by removing retaining snap ring. Separate synchronizer sleeve, hub, and blocking rings. Inspect all components for wear, scoring, or heat damage. Measure synchronizer ring-to-gear cone clearance using feeler gauges and compare to OEM wear limit (verify exact new/limit specification from factory manual for this transmission). Replace complete synchronizer assembly with new OEM unit (verify the correct gear-specific synchronizer part number against official Aston Martin/Graziano parts documentation). Install new blocking rings, hub, and sleeve, ensuring alignment marks are correctly oriented. Install retaining snap ring with opening positioned away from high-load area. Note: Measure synchronizer ring-to-gear cone clearance using feeler gauges and compare against the factory new/wear-limit specification for this transmission (verify exact values in OEM service data before condemning or accepting the ring).
12. 12

    Inspect and clean all components
    Thoroughly clean all shafts, bearings, and gears with solvent and compressed air. Inspect all bearing surfaces for scoring or discoloration. Check all gear teeth for wear or damage. Measure shaft runout using dial indicator (maximum typically 0.05mm). Replace any components showing wear beyond specification. Lubricate all components with the OEM-specified manual transaxle gear oil before reassembly (verify exact lubricant specification against Aston Martin documentation for this transaxle).
13. 13

    Reassemble gear clusters and shafts
    Install gear assemblies onto shafts in reverse order of removal, ensuring all thrust washers and shims are positioned correctly per documentation. Install bearings using appropriate driver, ensuring full seating. Install snap rings with openings positioned per factory specification. Verify gear endplay matches original measurements using dial indicator. Install shift forks onto synchronizer sleeves and position shift rails, ensuring detent engagement.
14. 14

    Seal and close transmission case
    Clean case mating surfaces thoroughly with brake cleaner and lint-free towels. Apply OEM anaerobic sealant to case mating surface per manufacturer pattern (typically thin continuous bead). Carefully lower upper case half onto assembly, ensuring shaft alignment and no component displacement. Install case fasteners hand-tight initially, then torque in cross-pattern sequence to OEM specification (value must be verified against official Aston Martin/ZF workshop documentation for this specific transmission model before assembly). Allow sealant to cure per manufacturer specification before fluid fill. Note: torque in cross-pattern sequence to the exact OEM specification (verify case-fastener torque from the factory manual for this specific transmission)
15. 15

    Install external components
    Reinstall solenoid pack, speed sensors, clutch actuators, and all external brackets to transmission case. Torque all fasteners to OEM specification. Reconnect hydraulic lines and bleed clutch actuator system per manufacturer procedure. Install new input and output shaft seals using appropriate seal driver.
16. 16

    Reinstall transmission to vehicle
    Position transmission on jack and raise into position, carefully aligning input shaft with clutch assembly. Slide transmission forward onto engine, ensuring full engagement. Install bellhousing-to-engine fasteners and torque to OEM specification (value must be verified against official Aston Martin workshop documentation). Install transmission mounts and crossmember, torquing all fasteners to specification. Reconnect propeller shaft, aligning marks made during removal, and torque coupling bolts to specification. Note: Install bellhousing-to-engine fasteners and torque to OEM specification (verify exact torque from factory manual for this engine/transmission).
17. 17

    Reconnect all systems and fill transmission
    Reconnect all electrical connectors and wiring harness clips. Reconnect hydraulic actuator lines. Install transmission drain plug with new crush washer and torque to specification. Fill transaxle with the correct OEM-specified MANUAL gear oil type and quantity using a fluid transfer pump through the fill port (verify exact fluid specification and capacity for the manual transaxle fitted). Reinstall undertray panels. Note: A manual transaxle uses gear oil, NOT ZF Lifeguard ATF — verify exact lubricant spec and capacity against Aston Martin documentation. capacity against Aston Martin documentation). Note: Fill transmission with the correct OEM-specified manual transmission gear oil through the fill port to the specified level (verify grade and capacity in factory service data).
    Torque spec

    Transmission Drain Plug30 Nm (22 lb-ft)
18. 18

    Perform clutch adaptation and system initialization
    Reconnect battery negative terminal. For the manual transmission, bleed the hydraulic clutch system and verify clutch engagement by road test; no electronic clutch adaptation is required. If equipped with the automatic (no synchros, not applicable to this job), use the Aston Martin diagnostic tool to clear codes and perform adaptation as specified. Note: Reconnect battery negative terminal. Clear any stored fault codes using the Aston Martin diagnostic tool if any were set during the repair. No clutch adaptation or electronic shift-point learning is required for the manual transaxle — verify against factory documentation whether any relearn is needed for the specific vehicle.

Reassembly

1. Reassembly follows disassembly in reverse order with attention to proper torque specifications and sealant application.
2. All snap rings must be installed with openings positioned per OEM specification to avoid rotation into load paths.
3. Shift fork engagement must be verified by manually cycling through all gear positions before case closure.
4. All selective shims and thrust washers must be reinstalled in original positions unless endplay measurements indicate replacement thickness is required.
5. Case sealant must cure for minimum time specified by sealant manufacturer before filling with fluid.
6. Hydraulic actuator system must be bled completely to remove all air from clutch circuits.
7. Propeller shaft alignment marks must be observed during reinstallation to maintain driveline balance.

Verification

• With vehicle raised and in neutral, manually rotate output flange to verify smooth rotation through all gear ranges without binding or unusual noise.
• Using diagnostic tool, verify all transmission sensors report correct values and no fault codes are present.
• Perform clutch adaptation procedure and verify successful completion with no errors.
• Start engine and verify transmission engages all gears smoothly without slipping, harshness, or grinding.
• Test drive vehicle through all gear ranges, verifying smooth shifts under light and moderate throttle.
• Check for fluid leaks at all case seams, shaft seals, and hydraulic connections after test drive.
• Re-check fluid level after test drive and top off if necessary (fluid expands when hot).
• Verify no new fault codes have been generated during test drive using diagnostic tool.

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