This procedure drains and refills the transfer case fluid on a 1966 Chevrolet Corvette, ensuring proper lubrication of the transfer case components.

Warnings

Tools required

Parts

• Transfer case drain plug washer/gasket × 1 — Use OEM specification
• Transfer case fill plug washer/gasket × 1 — Use OEM specification

Fluids

• 75W-90 GL-5 Gear Oil — 2 qt

Preparation

1. Park vehicle on level surface and apply parking brake firmly.
2. Place wheel chocks behind front wheels.
3. Raise rear of vehicle using appropriate jacking points and support securely on jack stands rated for vehicle weight.
4. Verify vehicle is stable before working underneath.
5. Locate the rear differential housing under the center of the vehicle between the rear wheels.

Procedure

1. 1

   Clean fill and drain plug areas
   Locate the fill plug on the passenger side of the differential housing and the drain plug on the bottom of the housing. Use a wire brush to clean around both plugs to prevent dirt from entering the differential when plugs are removed.
2. 2

   Remove fill plug first
   Using the appropriate socket, loosen and remove the fill plug from the passenger side of the differential housing. Removing the fill plug first ensures you can refill the differential after draining. If the fill plug is seized and cannot be removed, do not proceed with draining.
   ⚠Some fluid may seep out when the fill plug is removed. Have a rag ready.
3. 3

   Position drain pan and remove drain plug
   Position the drain pan directly under the drain plug on the bottom of the differential housing. Using the appropriate socket, slowly loosen the drain plug. Once loose, quickly remove it by hand and allow fluid to drain completely into the pan. This will take approximately 5-10 minutes.
   ⚠Fluid will flow quickly once plug is removed. Keep hands clear of the stream.
   Torque spec

   Transfer Case Drain Plug25 Nm (18 lb-ft)
4. 4

   Inspect drain plug and old fluid
   Examine the drain plug threads and sealing surface for damage. Check the magnetic drain plug (if equipped) for excessive metal particles. Inspect the drained fluid for metal shavings, water contamination, or unusual odor. Minor metallic residue is normal, but excessive debris may indicate differential damage requiring further inspection.
   ℹ️Some metal particles on magnetic drain plug are normal wear. Chunks or large amounts of metal indicate potential internal damage.
5. 5

   Install drain plug with new washer
   Clean the drain plug threads and sealing surface thoroughly. If the plug uses a sealing washer, install a new one; if it is a tapered pipe-thread plug, apply appropriate thread sealant instead. Thread the drain plug in by hand to ensure proper thread engagement, then torque to specification using a torque wrench.
   Torque spec

   Transfer Case Drain Plug25 Nm (18 lb-ft)
6. 6

   Fill differential with new gear oil
   Using a fluid pump or squeeze bottle with tube, insert the tube into the fill plug hole. Slowly pump fresh SAE 80W-90 GL-5 gear oil into the differential until fluid begins to seep out of the fill hole. The differential is full when fluid reaches the bottom of the fill plug threads. The capacity is approximately 1.5 to 1.75 quarts; fill to the bottom of the fill hole rather than to a fixed volume.
   ℹ️Fill slowly to allow air to escape and prevent overflow. Overfilling can cause seal leaks and fluid aeration.
7. 7

   Install fill plug with new washer
   Clean the fill plug threads and sealing surface. Install a new fill plug washer or gasket. Thread the fill plug in by hand until snug, then torque to specification using a torque wrench.
   Torque spec

   Transfer Case Fill Plug25 Nm (18 lb-ft)
8. 8

   Clean up and lower vehicle
   Wipe any spilled gear oil from the differential housing and surrounding components using shop rags. Remove the drain pan from under the vehicle. Carefully lower the vehicle from jack stands and remove jack stands and wheel chocks.

Reassembly

1. Ensure both fill and drain plugs are torqued to specification and not leaking.
2. Dispose of used gear oil at an approved recycling facility or auto parts store.
3. Clean all tools and store properly.

Verification

• Start engine and allow to idle for 1 minute, then shut off.
• Check around both fill and drain plugs for any signs of leakage.
• After driving approximately 10-15 miles, re-inspect both plugs for leaks.
• Monitor for any unusual noises from the differential during normal driving, which could indicate improper fill level or other issues.

More procedures for this vehicle