This procedure covers the removal and replacement of the transmission mount on a 1966 Chevrolet Corvette with 327ci V8, including supporting the transmission and crossmember removal.

Warnings

Tools required

Parts

• Transmission mount (rubber cushion/insulator) × 1 — Use OEM specification

Preparation

1. Park vehicle on level, solid ground and engage parking brake firmly
2. If equipped with manual transmission, place in first gear; if automatic, place in Park
3. Chock rear wheels securely
4. Raise front of vehicle using floor jack at front crossmember jacking point
5. Install jack stands under frame rails just behind front suspension crossmember
6. Lower vehicle onto jack stands and verify stability before proceeding
7. Apply penetrating oil to all crossmember and transmission mount fasteners; allow 10-15 minutes to penetrate

Procedure

1. 1

   Position transmission jack
   Position the transmission jack under the transmission oil pan. Place a wood block between the jack saddle and the oil pan to distribute load and prevent pan damage. Raise the jack until it just contacts the pan with light pressure, but is not yet supporting the transmission weight. Ensure the jack is centered and stable.
2. 2

   Identify and access crossmember bolts
   Locate the four crossmember-to-frame bolts. Two bolts secure each end of the transmission crossmember to the frame rails. Verify the head size of these crossmember-to-frame bolts (commonly 3/4" head on original GM hardware) before selecting a socket. Verify you have clear access to all four bolts before proceeding.
3. 3

   Remove crossmember bolts
   Using the correct socket for your fasteners (verify head size, commonly 3/4") with extension, remove all four crossmember-to-frame bolts. Start by loosening each bolt 2-3 turns in a cross pattern, then remove completely. Retain all bolts and any washers for reinstallation. The crossmember will remain in position, supported by the transmission mount.
4. 4

   Support transmission weight
   Carefully raise the transmission jack to take the full weight of the transmission and transfer load away from the mount. Raise only enough to unload the mount (approximately 1/4" to 1/2" of lift). You should see a slight gap appear between the transmission mount and crossmember when weight is properly transferred.
5. 5

   Lower crossmember
   With transmission weight now on the jack and all four crossmember-to-frame bolts removed, carefully lower the crossmember by hand. The crossmember is now fully detached from the frame and can be lowered straight down to access the transmission mount bolts.
6. 6

   Remove transmission mount-to-crossmember bolts
   Locate the two bolts securing the transmission mount to the crossmember. These are accessed from underneath; verify the correct socket size for your mount fasteners before removal. Remove both bolts completely and retain for reinstallation. The mount bracket remains attached to the transmission tailhousing.
7. 7

   Remove transmission mount-to-transmission bolts
   Locate the two bolts securing the transmission mount bracket to the transmission tailhousing. Verify the correct head size for the mount-to-tailhousing bolts before removal; access is typically from the side. Remove both bolts and lower the mount assembly away from the transmission. Inspect the old mount for cracking, separation, or oil saturation.
8. 8

   Clean mounting surfaces
   Use a wire brush to clean the transmission tailhousing mounting surface and the crossmember mounting pad. Remove all dirt, rust, and old rubber residue. Inspect both surfaces for cracks or damage. The mounting surfaces must be clean and flat for proper new mount seating.
9. 9

   Install new transmission mount to transmission
   Position the new transmission mount bracket to the transmission tailhousing, aligning the bolt holes. Install the two mount-to-transmission bolts finger-tight. Ensure the mount is oriented correctly with the rubber cushion positioned to mate with the crossmember pad.
10. 10

    Torque transmission mount-to-transmission bolts
    Using a torque wrench, tighten the two transmission mount-to-transmission bolts evenly and alternately to the manufacturer-specified torque value (verify against the GM service manual for your transmission). This ensures proper clamping force and mount alignment.
    Torque spec

    Transmission Mount Bolts65 Nm (48 lb-ft)
11. 11

    Raise crossmember into position
    Raise the crossmember by hand until the transmission mount rubber cushion seats into the crossmember pad. Align the crossmember bolt holes with the frame rail holes. You may need to use the transmission jack to raise or lower the transmission slightly (no more than 1/8") to achieve perfect alignment.
12. 12

    Install crossmember-to-mount bolts
    Install the two bolts securing the crossmember to the transmission mount bracket. Thread them in by hand first to ensure proper alignment, then snug them down with a socket wrench but do not torque yet.
13. 13

    Install crossmember-to-frame bolts
    Install all four crossmember-to-frame bolts with any original washers. Start all bolts by hand to ensure threads engage properly. Tighten in a cross pattern (front left, rear right, front right, rear left) to draw the crossmember up evenly to the frame.
14. 14

    Torque crossmember bolts
    Using a torque wrench, tighten all four crossmember-to-frame bolts to the manufacturer-specified torque (verify against the GM 1966 Corvette service manual) in the same cross pattern. This ensures the crossmember is properly secured and load is distributed evenly.
    Torque spec

    Crossmember Bolts95 Nm (70 lb-ft)
15. 15

    Lower transmission onto mount
    Carefully lower the transmission jack to transfer the transmission weight back onto the new mount. Lower slowly and verify the mount compresses evenly and the transmission seats properly into the crossmember. Continue lowering until the jack is no longer supporting any weight.
16. 16

    Remove transmission jack
    Once the transmission weight is fully on the mount, remove the transmission jack and wood block from under the vehicle. Verify visually that the mount is compressed evenly and the crossmember is seated flush against the frame rails at all four bolt locations.

Reassembly

1. No disassembly of other components was required for this procedure

Verification

• With vehicle still on jack stands, grab the tailshaft housing and attempt to move it vertically - there should be minimal movement with the new mount properly installed
• Visually inspect all four crossmember bolts and verify they are tight and the crossmember is flush to the frame
• Check that the transmission mount rubber cushion is compressed evenly without visible gaps or misalignment
• Lower vehicle from jack stands and test drive - verify no excessive vibration or clunking when shifting or accelerating
• Re-check torque on all fasteners after 50-100 miles of driving

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