This procedure covers the removal and replacement of the transmission mount on a 1970 AMC Rebel Machine with 390ci V8 and rear-wheel drive transmission.

Warnings

Tools required

Parts

• Transmission mount × 1 — Use OEM specification for BorgWarner or Torque Command automatic transmission
• Transmission mount fastener kit (if hardware is corroded) × 1 — Optional replacement hardware

Preparation

1. Park vehicle on level, solid ground and engage parking brake firmly
2. If equipped with manual transmission, place shifter in first gear. If automatic, place in Park
3. Allow exhaust system to cool completely if vehicle was recently operated
4. Chock rear wheels to prevent vehicle movement
5. Disconnect negative battery cable to prevent electrical shorts during work
6. Apply penetrating oil to all transmission mount fasteners and allow to soak for 15-20 minutes

Procedure

1. 1

   Raise and support vehicle
   Raise the front of the vehicle using a floor jack at the front crossmember. Install jack stands under the frame rails at approved jacking points. Ensure vehicle is stable and level. Lower jack slightly so weight rests on stands, but keep jack in position as backup support.
2. 2

   Locate transmission mount
   From underneath the vehicle, locate the transmission mount assembly. The mount is positioned on the transmission tailshaft housing extension and bolts to a crossmember that spans the frame rails. On the 1970 Rebel, this is typically 12-18 inches forward of the rear axle. Inspect the mount for visible damage, cracks, or separation.
3. 3

   Support transmission
   Position a transmission jack or second floor jack under the transmission oil pan. Place a wood block between the jack and pan to distribute load and prevent pan damage. Raise jack until it just contacts the transmission and supports the weight, but do not lift the transmission yet. The transmission should be stable but not under upward pressure.
4. 4

   Remove crossmember-to-frame bolts
   Locate the bolts securing the transmission crossmember to the frame rails on both sides. These are typically two bolts per side, though configuration may vary. Remove all four crossmember-to-frame bolts using the appropriate socket and ratchet. Support the crossmember by hand as you remove the final bolts to prevent it from falling.
5. 5

   Remove transmission mount-to-crossmember fasteners
   With the crossmember still in place but free from the frame, remove the nuts or bolts securing the transmission mount to the crossmember. These typically thread up from below through the mount isolator. Keep track of any washers or spacers in the assembly.
6. 6

   Lower crossmember
   Carefully lower the crossmember away from the transmission mount. You may need to slightly raise the transmission with the jack to provide clearance. Set the crossmember aside in a safe location. Inspect for damage or excessive corrosion.
7. 7

   Remove transmission mount-to-transmission fasteners
   Locate and remove the bolts securing the transmission mount to the transmission extension housing. These typically require a socket with extension due to limited access. There are usually 2-4 bolts depending on mount configuration. Support the mount as you remove the last fastener.
8. 8

   Remove old transmission mount
   With all fasteners removed, pull the old transmission mount away from the transmission. You may need to use a pry bar to break it free if rubber has bonded to metal surfaces over time. Inspect the mount for tears, cracks, or separation of rubber from metal backing plates.
9. 9

   Clean mounting surfaces
   Use a wire brush to clean the transmission extension housing mounting surface and the crossmember mounting surface. Remove all rust, old rubber residue, and debris. Ensure surfaces are clean and flat for proper new mount seating.
10. 10

    Install new transmission mount to transmission
    Position the new transmission mount on the transmission extension housing, aligning bolt holes. Install the mount-to-transmission bolts and tighten by hand. Verify proper alignment and orientation of the mount before final tightening. Torque to manufacturer specification (typically 35-45 ft-lbs, but verify for your specific application).
11. 11

    Position crossmember
    Raise the transmission slightly with the jack to align the new mount with the crossmember position. Lift the crossmember into place, aligning the mount through the crossmember opening and the crossmember bolt holes with the frame rail holes. This step may require an assistant or temporary support.
12. 12

    Install crossmember fasteners
    Start all four crossmember-to-frame bolts by hand to ensure proper thread engagement and alignment. Once all bolts are started, tighten them in a cross pattern (front left, rear right, front right, rear left) to ensure even loading. Torque to manufacturer specification (typically 25-35 ft-lbs, but verify for your specific application).
13. 13

    Install mount-to-crossmember fasteners
    Install the nuts or bolts securing the transmission mount to the crossmember. Ensure any spacers or washers are in their correct positions. Tighten fasteners evenly. Torque to manufacturer specification (typically 30-40 ft-lbs, but verify for your specific application).
14. 14

    Remove transmission support and lower vehicle
    Carefully lower the transmission jack or floor jack supporting the transmission, allowing the transmission weight to settle onto the new mount. Remove the jack and wood block from under the transmission. Raise vehicle slightly off jack stands, remove stands, and lower vehicle to ground.

Reassembly

1. Reconnect negative battery cable
2. Remove wheel chocks
3. Inspect underside of vehicle for any tools or parts left behind

Verification

• Start engine and verify no unusual vibrations that would indicate improper mount installation
• With engine running, shift through all gear positions (or depress clutch for manual) and verify smooth operation without excessive movement
• Visually inspect mount installation from underneath with engine running to confirm proper positioning and no contact with crossmember or frame
• Road test vehicle and verify no excessive vibration, clunking, or drivetrain movement during acceleration and deceleration
• After initial test drive, re-inspect all fasteners for proper torque and check for any loosening

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