Dual Mass Flywheel

This procedure removes the transmission and clutch assembly to replace the dual mass flywheel on a 1966 Chevrolet Corvette with a 327ci V8 engine.

Warnings

Tools required

Parts

• Dual mass flywheel assembly × 1 — Use OEM specification
• Clutch disc × 1 — Use OEM specification
• Pressure plate × 1 — Use OEM specification
• Pilot bearing or bushing × 1 — Use OEM specification
• Transmission input shaft seal × 1 — Use OEM specification
• Rear main seal (if leaking) × 1 — Use OEM specification
• Transmission gasket/seal kit × 1 — Use OEM specification
• Thread locker (medium strength) × 1 — Loctite 242 or equivalent

Fluids

• 75W-90 GL-5 Gear Oil — 2 qt

Preparation

1. Park vehicle on level ground and engage parking brake.
2. Disconnect negative battery cable.
3. Raise vehicle and support securely on four jack stands, providing adequate working clearance underneath.
4. Remove the exhaust system from the manifolds back to the mufflers to provide clearance for transmission removal.
5. Mark the driveshaft-to-differential flange relationship with paint or marker for proper reinstallation.
6. Drain transmission fluid into appropriate container.
7. Remove the driveshaft by removing the 4 U-bolts at the rear differential, then sliding the driveshaft rearward out of the transmission.
8. Disconnect the clutch linkage from the clutch fork and remove the clutch return spring.
9. Disconnect the speedometer cable from the transmission.
10. Disconnect all electrical connections to the transmission (backup light switch if equipped).

Procedure

1. 1

   Support engine and remove transmission crossmember
   Place a floor jack with a block of wood under the engine oil pan to support the engine weight. Remove the 2 bolts securing the transmission mount to the crossmember. Remove the 4 bolts securing the crossmember to the frame and remove the crossmember from the vehicle.
2. 2

   Remove transmission mounting bolts
   Position the transmission jack under the transmission and secure it with the safety chain. Remove the 4 bellhousing-to-engine block bolts. On the 1966 Corvette 327, these are located at approximately 2, 5, 7, and 10 o'clock positions when viewing from the rear of the engine.
3. 3

   Separate and remove transmission
   Carefully slide the transmission rearward, keeping it level and aligned with the engine to avoid damaging the clutch disc or input shaft. The transmission must move straight back approximately 1.5 inches to clear the clutch splines before it can be tilted or lowered. Once clear of the clutch assembly, carefully lower the transmission on the jack and roll it out from under the vehicle.
4. 4

   Inspect and mark clutch assembly orientation
   With the transmission removed, inspect the clutch disc, pressure plate, and flywheel for wear, hot spots, or damage. Mark the pressure plate-to-flywheel relationship with a paint marker to maintain balance during reassembly if reusing the pressure plate.
5. 5

   Remove pressure plate
   Using the flywheel holding tool to prevent rotation, loosen the 6 pressure plate bolts in a star pattern, approximately 2 turns at a time, to gradually release spring tension. Remove all bolts and carefully remove the pressure plate and clutch disc as an assembly. Keep the clutch disc clean and do not allow grease or oil to contact the friction surfaces.
6. 6

   Remove flywheel
   Install the flywheel holding tool to lock the flywheel in position. Remove the 6 flywheel mounting bolts. The flywheel is heavy, so support it while removing the final bolts. Carefully remove the flywheel from the crankshaft flange.
7. 7

   Inspect crankshaft flange and pilot bearing
   Clean the crankshaft flange thoroughly with brake cleaner and a wire brush, removing any old thread locker residue. Inspect the crankshaft flange for cracks or damage. Remove the pilot bearing or bushing from the crankshaft using a slide hammer with internal puller attachment or a pilot bearing puller tool.
8. 8

   Install new pilot bearing
   Pack the new pilot bearing lightly with high-temperature bearing grease (do not overfill). Drive the new pilot bearing into the crankshaft bore until it is flush or slightly recessed (approximately 0.030-0.060 inch below the crankshaft face), using a pilot bearing installation tool or appropriately sized socket that contacts only the outer race.
9. 9

   Install new dual mass flywheel
   Clean the crankshaft bolt holes with brake cleaner to remove any oil. Apply medium-strength thread locker to the threads of the 6 flywheel bolts. Position the new dual mass flywheel onto the crankshaft flange, aligning the dowel pins if equipped. Install all 6 bolts finger-tight, then torque in a star pattern to the manufacturer's specification (typically 55-70 ft-lb for small block Chevy, but verify with flywheel manufacturer). Use the flywheel holding tool to prevent rotation during tightening.
10. 10

    Install new clutch disc and pressure plate
    Insert the clutch alignment tool through the new clutch disc and into the pilot bearing to hold the disc centered. Position the clutch disc with the side marked 'flywheel side' or the protruding hub side facing the transmission. Place the new pressure plate over the clutch disc, aligning any balance marks if reusing the original pressure plate, or positioning the pressure plate with any balance weights in the same orientation as removed. Install the 6 pressure plate bolts finger-tight.
11. 11

    Torque pressure plate and verify alignment
    Tighten the 6 pressure plate bolts in a star pattern, gradually and evenly, approximately 3 turns at a time until fully seated. Torque to manufacturer specification (typically 25-35 ft-lb for stock Corvette pressure plates). Verify the clutch alignment tool still moves freely and can be removed and reinstalled easily, confirming proper clutch disc centering.
12. 12

    Prepare transmission for installation
    Clean the transmission input shaft splines with brake cleaner. Apply a very light coating of high-temperature bearing grease to the input shaft splines (avoid excess grease that could contaminate the clutch). Inspect and replace the transmission input shaft seal if there is any evidence of leakage. Verify the clutch release bearing slides freely on the transmission bearing retainer.
13. 13

    Install transmission
    Position the transmission on the transmission jack and carefully raise it into position, aligning the input shaft with the clutch disc splines. The transmission must remain level and aligned as it moves forward. Gently rotate the transmission output shaft to help the input shaft splines engage with the clutch disc. Once the splines engage, slide the transmission forward until the bellhousing contacts the engine block. Do not force the transmission forward or use bolts to draw it in - it should slide in with moderate hand pressure once properly aligned.
14. 14

    Install transmission mounting bolts and crossmember
    Install the 4 bellhousing-to-engine block bolts and tighten in a cross pattern to proper torque specification (typically 30-40 ft-lb for bellhousing bolts). Raise the transmission slightly with the jack to align the transmission mount with the crossmember position. Install the crossmember and secure with the 4 frame bolts. Install the 2 transmission mount-to-crossmember bolts. Remove the transmission jack and engine support jack.
15. 15

    Reconnect driveline and components
    Apply a light coating of grease to the slip yoke splines. Slide the driveshaft forward into the transmission, then raise the rear and align the marks made during disassembly. Install the 4 U-bolts at the differential flange and torque to specification (typically 15-20 ft-lb). Reconnect the clutch linkage to the clutch fork and install the clutch return spring. Reconnect the speedometer cable and all electrical connections. Reinstall the exhaust system with new gaskets if needed.
16. 16

    Refill transmission and final checks
    Refill the transmission with the proper type and quantity of gear oil (2.0 quarts of 75W-90 GL-5 for most manual transmissions). Reconnect the negative battery cable. Lower the vehicle to the ground. Adjust the clutch linkage per factory specifications to achieve proper pedal height and free play (typically 1-1.5 inches of free play at the pedal).

Reassembly

1. Torque all fasteners to proper specifications in the sequence described.
2. Ensure all electrical connections and linkages are properly reconnected and secured.
3. Verify adequate transmission fluid level before operation.
4. Double-check that all tools have been removed from the vehicle and work area.

Verification

• Start the engine with the clutch pedal depressed and verify no abnormal noises from the flywheel or clutch area.
• With the engine running at idle, verify the clutch disengages completely by shifting through all gears without grinding.
• Test drive the vehicle and verify smooth clutch engagement without chatter, slipping, or vibration.
• Verify no fluid leaks from the transmission or rear main seal after test drive.
• Check for proper clutch pedal feel and complete engagement/disengagement throughout the pedal travel.
• Listen for any abnormal noises during acceleration and deceleration that might indicate flywheel imbalance or improper installation.

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