Overdrive Solenoid

This procedure covers the replacement of the overdrive solenoid in the Powerglide automatic transmission used in the 1966 Chevrolet Corvette with the 327ci V8 engine.

Warnings

Tools required

Parts

• Overdrive solenoid assembly × 1 — Use OEM specification
• Transmission pan gasket × 1 — Use OEM specification
• Transmission filter × 1 — Use OEM specification

Fluids

• Dexron III ATF — 5 qt

Preparation

1. Park vehicle on level surface and engage parking brake firmly
2. Place wheel chocks behind rear wheels
3. Allow transmission to cool if vehicle has been recently operated
4. Gather all tools, parts, and fluids before beginning
5. Raise vehicle using floor jack at rear differential or frame jacking points
6. Support vehicle securely on jack stands rated for vehicle weight
7. Position drain pan beneath transmission pan

Procedure

1. 1

   Drain transmission fluid
   Loosen all transmission pan bolts gradually, starting from one corner. Leave two bolts at opposite corners slightly tight to control pan drop. Carefully lower one corner of pan to allow fluid to drain into drain pan. Once majority of fluid has drained, remove remaining bolts and lower pan completely. Be prepared for residual fluid spillage.
2. 2

   Remove transmission pan and filter
   With pan removed, set aside and inspect for debris or metal particles. Remove the transmission filter by pulling straight down from the valve body. The filter is typically held by friction fit or a single bolt depending on configuration.
3. 3

   Locate overdrive solenoid
   With pan and filter removed, locate the overdrive solenoid mounted on the valve body. The solenoid is a cylindrical component with an electrical connector and is typically mounted on the driver's side of the valve body with 2 bolts securing it in place.
4. 4

   Disconnect solenoid electrical connector
   Carefully disconnect the electrical connector from the solenoid. Note the connector orientation for reinstallation. If connector is corroded or difficult to remove, gently work it back and forth while pulling. Do not force or pull on wires.
5. 5

   Remove solenoid mounting bolts
   Remove the 2 bolts securing the solenoid to the valve body. Keep track of bolt locations as they may be different lengths. The solenoid may have internal spring pressure, so control it as you remove the final bolt.
6. 6

   Extract solenoid assembly
   Carefully pull the solenoid straight out from the valve body bore. Note the orientation and position of any O-rings, seals, or springs that come out with the solenoid. Some ATF will drain from the bore. Inspect the bore for debris or damage.
7. 7

   Inspect valve body bore
   Clean the valve body bore where the solenoid seats using a clean shop rag. Do not use abrasive materials that could damage the bore. Check for scoring, cracks, or debris. Ensure the solenoid passage is clear and undamaged.
8. 8

   Install new solenoid
   Lubricate new solenoid O-rings with clean ATF. Insert new solenoid into valve body bore in the same orientation as the original, ensuring it seats fully. Align mounting holes with valve body.
9. 9

   Install solenoid mounting bolts
   Install the 2 mounting bolts and tighten in a crisscross pattern. Tighten to snug specification first, then final torque. Without factory torque specification, tighten to 8-10 ft-lbs to avoid stripping aluminum valve body threads.
10. 10

    Reconnect electrical connector
    Reconnect the electrical connector to the new solenoid, ensuring it clicks or seats fully. Verify connector is secure and properly oriented. Check wire routing to ensure no interference with pan installation.
11. 11

    Install new transmission filter
    Install the new transmission filter by pushing it firmly onto the pickup tube until it seats completely. If filter has a mounting bolt, install and tighten securely.
12. 12

    Clean transmission pan and mating surface
    Thoroughly clean the transmission pan and transmission case mating surface using gasket scraper and wire brush. Remove all old gasket material and ensure surfaces are clean and flat. Wipe surfaces with clean shop rag to remove debris.
13. 13

    Install new gasket and transmission pan
    Position new gasket on transmission pan or case (depending on gasket type). Carefully lift pan into position, aligning all bolt holes. Start all pan bolts by hand to ensure proper alignment before tightening any bolts.
14. 14

    Torque transmission pan bolts
    Tighten pan bolts in a spiral pattern from center outward. Tighten Powerglide pan bolts to approximately 12-13 ft-lbs (verify against factory service manual) to compress gasket adequately without distorting pan. Do not overtighten as this will cause leaks.
15. 15

    Refill transmission with ATF
    Lower vehicle to ground. Add approximately 4 quarts of Dexron/Mercon-compatible ATF (Type A Suffix A original spec; a modern Dexron III/Mercon fluid is acceptable as a backward-compatible substitute) through dipstick tube using funnel. Start engine and allow to idle. With engine running and parking brake engaged, shift through all gear positions, pausing 2-3 seconds in each. Return to Park and check fluid level with engine running. Add fluid as needed to bring level to proper mark on dipstick. Total refill quantity will be approximately 5 quarts.

Reassembly

1. Reinstallation follows removal in reverse order
2. Ensure all electrical connections are secure and properly routed
3. Verify transmission pan bolts are torqued evenly to prevent leaks
4. Do not overfill transmission, as this can cause foaming and shifting issues

Verification

• Start engine and verify no ATF leaks from transmission pan or solenoid area
• With engine at operating temperature, verify transmission shifts properly through all gears
• Test drive vehicle and confirm overdrive engagement and disengagement functions correctly
• Recheck transmission fluid level after test drive with engine running and transmission in Park
• Monitor for any unusual noises or shifting behavior that could indicate improper solenoid installation

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