Synchros - All

Complete transmission disassembly and synchronizer ring replacement for all six forward gears in the ZF 6HP26 automatic transmission, requiring transmission removal, case splitting, and selective shaft endplay measurement.

Warnings

Tools required

Parts

• Synchronizer ring set (6-speed complete) × 1 — Use OEM ZF specification
• Transmission case gasket × 1 — Use OEM specification
• Transmission oil pan gasket × 1 — Use OEM specification
• Transmission filter × 1 — Use OEM specification
• Transmission drain plug crush washer × 1 — Use OEM specification
• Input shaft seal × 1 — Use OEM specification
• Output shaft seal × 1 — Use OEM specification
• Mechatronic valve body gasket set × 1 — Use OEM specification
• Selective shim set (assorted thicknesses) × 1 — Use OEM ZF specification
• Thread locking compound (medium strength) × 1 — Loctite 243 or equivalent

Fluids

• Touchtronic 6-speed ZF ATF — 10.5 qt

Preparation

1. Park vehicle on level lift or ramps with adequate clearance for transmission removal from below.
2. Disconnect negative battery cable and secure away from terminal.
3. Remove engine undertray panels and rear undertray to access transmission.
4. Place drain pan capable of holding 12 quarts under transmission drain plug.
5. Drain transmission fluid completely and remove drain plug crush washer.
6. Remove transmission oil pan and filter after fluid has drained.
7. Clean work area and prepare clean assembly table with lint-free cloths for internal component layout.
8. Label all electrical connectors and fluid lines with tape tags before disconnection.

Procedure

1. 1

   Remove Transmission from Vehicle
   Support engine with support fixture or crane. Disconnect propeller shaft at transmission flange (note alignment marks on flange for reassembly). If automatic-equipped, disconnect transmission cooler lines at the transaxle and plug lines to prevent contamination (manual transaxle has no cooler lines). NOTE: The DB9 uses a rear-mounted transaxle connected to the engine by a torque tube/propeller shaft; the gearbox is not bolted directly to an engine bellhousing—disconnect the torque tube at the transaxle and support accordingly. Disconnect the shift linkage/cable or shift-by-wire actuator at the transaxle as applicable to the fitted gearbox. Disconnect all electrical connectors from transmission case and mechatronic unit. Remove transmission/transaxle mounting bolts at the chassis/subframe mounting points (verify exact count and fastener type against factory documentation for the DB9 rear transaxle). Support transmission with transmission jack and secure with safety chains. Remove bellhousing-to-engine bolts (count and note locations as bolt lengths vary). Carefully lower the transaxle while disengaging the clutch splines from the input shaft. For automatic-equipped vehicles instead guide the torque converter away from the flexplate and verify it remains seated in the pump during removal. Note: Disconnect transmission cooler lines at the rear transaxle (plug lines to prevent contamination). Note: on the DB9 the torque converter is mounted at the engine (front) and the transaxle is at the rear, connected by a torque tube — follow the rear-transaxle removal sequence accordingly. Note: Disconnect the negative battery cable (battery is located in the rear luggage compartment on the DB9) and wait 15 minutes before starting work to allow airbag system capacitors to discharge.
2. 2

   Remove Torque Converter and External Components
   Remove the clutch assembly components from the input shaft if still attached. Place transaxle on a secure workbench. Remove external shift mechanism/selector housing, reverse light switch, and any external linkage. Photograph or diagram all component positions before removal. loose. Remove speed sensors and solenoid pack assemblies. Remove parking pawl actuator assembly. Photograph or diagram all component positions before removal.
3. 3

   Split Transmission Case
   Remove all case half fasteners (Torx bolts around perimeter of case). Install case spreader tool at designated lift points on case seam. Gently spread case halves using spreader tool while tapping lightly with plastic mallet around seam perimeter. Do not force separation—if case does not separate easily, verify all fasteners have been removed. Once separated, carefully lift upper case half vertically to expose internal geartrain. Note position of all thrust washers and bearings as case is opened. Photograph geartrain layout for reassembly reference.
4. 4

   Remove Geartrain Assembly
   Remove the geartrain in order for the Graziano manual: lift out the input (primary) shaft and output (mainshaft) assemblies together with the layshaft/countershaft, noting the orientation of all gears, synchronizer assemblies, and selector forks. Place all components on a clean work surface in order of removal. Keep thrust washers with their corresponding shafts—these are selective fit components. Place all components on clean work surface in order of removal. Keep thrust washers with their corresponding shafts—these are selective fit components.
5. 5

   Disassemble Input Shaft and Access Synchronizers
   Secure input shaft in padded vise or holding fixture. Remove snap rings retaining gear assemblies on input shaft. Note that synchronizer service applies ONLY to the Graziano 6-speed manual transaxle—the ZF 6HP26 automatic contains no synchronizer rings and achieves gear changes via hydraulically actuated multi-plate clutches controlled by the mechatronic unit. For the Graziano manual: use hydraulic press with proper arbor plates to remove pressed-on gears. As each gear is removed, extract synchronizer ring from behind gear. Inspect synchronizer ring engagement teeth for wear, scoring, or heat discoloration. Measure synchronizer ring gap with feeler gauges (gap should be within specification when ring is pressed onto cone surface). Mark each synchronizer position for correct reassembly. Note: Note that the ZF 6HP26 is a planetary-gear automatic transmission and contains NO synchronizer rings; shifting is performed by multi-plate clutches and brakes controlled by the mechatronic unit.
6. 6

   Disassemble Output Shaft and Access Remaining Synchronizers
   Secure output shaft in holding fixture. Remove output shaft snap rings and retaining hardware. Use press to remove gears from output shaft, extracting synchronizer rings as gears are removed. The output shaft typically contains synchronizer assemblies for multiple gear positions. Remove each synchronizer ring carefully to avoid damage to cone surfaces. Inspect all cone surfaces on gears for scoring or blue heat discoloration. Clean all components thoroughly with solvent and dry with compressed air.
7. 7

   Inspect and Measure Gear Cone Surfaces
   Inspect all gear cone surfaces that mate with synchronizer rings. Check for scoring, excessive wear, or heat damage. Use micrometer to measure cone diameter at multiple points around circumference. Compare measurements to service specifications. Any cone showing damage or out-of-specification wear requires gear replacement. Light scoring may be polished with fine emery cloth, but deep scoring requires gear replacement. Clean all cone surfaces to bare metal before installing new synchronizer rings.
8. 8

   Install New Synchronizer Rings on Input Shaft
   Install new synchronizer rings onto gear cone surfaces before pressing gears onto input shaft. Verify correct orientation of synchronizer ring engagement teeth (teeth must face direction of shift collar engagement). Apply light coat of assembly lubricant to cone surfaces. Place synchronizer ring onto cone and verify ring rotates freely with spring tension. Use hydraulic press with proper arbor plates to press gears onto input shaft in reverse order of removal. Install snap rings after each gear, verifying snap ring is fully seated in groove. Measure endplay of each gear after installation using dial indicator—endplay must be within selective shim specification range.
9. 9

   Install New Synchronizer Rings on Output Shaft
   Install new synchronizer rings onto output shaft gear cone surfaces using same procedure as input shaft. Verify correct orientation and engagement tooth direction. Press gears onto output shaft in correct order using hydraulic press and arbor plates. Install all snap rings and verify full seating. Measure shaft endplay at each gear position using dial indicator. Select appropriate thrust washers or selective shims to achieve specified endplay. Record all endplay measurements for quality control verification.
10. 10

    Reassemble Geartrain into Case
    Lubricate all thrust washers and bearing surfaces with ATF. Install output shaft assembly into lower case half with all thrust washers in correct positions. Install input shaft assembly with selective thrust washers. Install clutch pack assemblies in correct order (typically A, B, C, D, E clutches). Install compound planetary gear sets, verifying proper mesh of all gears. Install all selective thrust bearings and washers, ensuring they remain positioned during case closure. Double-check that all components rotate freely without binding.
11. 11

    Close Transmission Case
    Apply thin bead of transmission case sealant to lower case half mating surface per manufacturer specification (do not over-apply as excess will contaminate transmission). Carefully lower upper case half onto lower case, guiding all shafts through bearing bores. Install case spreader tool and gently compress case halves together. Install all case bolts hand-tight first, then torque in criss-cross pattern from center outward. Rotate input and output shafts to verify free rotation without binding after case is torqued. Any binding indicates misalignment or incorrect thrust washer selection.
12. 12

    Install Mechatronic Unit and External Components
    Install new valve body gasket onto case. Carefully position mechatronic valve body assembly, ensuring all check balls and springs are in correct positions. Install valve body bolts and torque in sequence from center outward per service specifications. Connect all internal wiring harness connectors. Install speed sensors and solenoid assemblies with new O-rings. Install parking pawl actuator. Install new transmission filter and oil pan with new gasket.
13. 13

    Install Transmission into Vehicle
    Install new input shaft seal and output shaft seal into case. Apply light coat of grease to torque converter hub and verify torque converter is fully seated in pump (measure from bellhousing face to torque converter ear—dimension should match specification). Raise transmission into position using transmission jack. Guide torque converter onto flexplate while aligning bellhousing to engine. Install bellhousing-to-engine bolts and torque per specification. Install transmission crossmember and torque mounting bolts. Reconnect propeller shaft, aligning marks made during removal. Reconnect cooler lines, shift cable, and all electrical connectors. Install new drain plug crush washer and install drain plug.
14. 14

    Fill Transmission and Perform Initial Tests
    Fill the Graziano manual transaxle with the manufacturer-specified gear oil and quantity through the fill plug (verify exact capacity against the DB9 workshop manual; the Graziano manual holds considerably less than the automatic—on the order of 2–3 quarts of the specified manual transaxle oil, NOT 10.5 quarts of ATF). Start engine and allow to idle. Shift through all gear positions with foot on brake, pausing 3 seconds in each position. Check fluid level per the level-plug procedure with transmission fluid at the specified temperature range; add fluid until it just overflows the level plug, then reinstall the plug. This transaxle has no dipstick. Check for leaks at all connection points, pan gasket, and case seam. Perform initial road test: verify all forward gears engage smoothly without slipping, verify reverse engagement, verify no abnormal noises. Return to shop and recheck fluid level and leak inspection. Note: Fill transmission with ZF-specification ATF per service manual (approximately 10.5 quarts total fill; verify exact quantity against the DB9 workshop manual) through the fill tube. Note: Fill transmission with the specified ZF-specification ATF quantity through the fill tube (verify exact service refill capacity against factory spec; dry-fill and refill volumes differ). Ensure capacity matches the fluids section value. Note: Check transaxle fluid level at the manufacturer-specified fluid temperature via the level plug; this transaxle has no dipstick.

Reassembly

1. Reassembly is detailed within removal steps above, as transmission case must be closed during procedure.
2. All synchronizer rings must be installed with engagement teeth facing correct direction per gear position.
3. All selective thrust washers and shims must be measured and installed to achieve proper shaft endplay.
4. New gaskets and seals must be used for case, valve body, oil pan, and all shaft seals.
5. Torque converter must be fully seated in pump before transmission installation—verify seating depth measurement.

Verification

• Verify all gears engage smoothly without delay or harshness during stationary shift test.
• Verify no transmission fluid leaks at pan, case seam, cooler lines, or shaft seals after initial run.
• Perform road test with scan tool connected: monitor all clutch pressure readings and shift timing values to verify normal operation.
• Verify smooth 1-2, 2-3, 3-4, 4-5, and 5-6 upshifts under light throttle—no flare or slipping.
• Verify kickdown shifts occur smoothly at wide-open throttle without excessive harshness.
• Verify manual shift mode operates correctly through all gears.
• Check transmission fluid level at operating temperature and verify level is within hot range on dipstick.
• Recheck all fastener torque values after road test.
• Clear any stored transmission fault codes and verify no new codes set after test drive.

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