Transmission Fluid Change

This procedure drains and refills the automatic transmission fluid in a 1970 AMC Rebel Machine with 390ci V8 engine, improving transmission performance and longevity.

Warnings

Tools required

Parts

• Automatic transmission pan gasket × 1 — Use OEM specification for Borg-Warner or Chrysler Torqueflite transmission
• Transmission filter and pickup tube seal × 1 — Verify transmission type before ordering

Fluids

• Automatic transmission fluid (Type A or Dexron) — 6 qt

Preparation

1. Park vehicle on level, solid surface and apply parking brake firmly
2. Place wheel chocks behind rear wheels
3. Allow transmission to cool if vehicle was recently operated
4. Verify correct replacement transmission filter and gasket for your specific transmission model
5. Prepare clean workspace and lay out drain pan, tools, and new parts

Procedure

1. 1

   Raise and support vehicle
   Raise the front of the vehicle using a floor jack at the front crossmember. Once raised to working height, place jack stands under the frame rails just behind the front wheels. Lower the vehicle onto the jack stands and verify stability before working underneath. The vehicle should be level to ensure proper fluid drainage and refill.
2. 2

   Locate transmission pan
   Position yourself under the vehicle and locate the transmission oil pan. It is mounted to the bottom of the transmission case, directly behind the engine oil pan. The pan is rectangular and held by approximately 13-17 bolts around the perimeter.
3. 3

   Position drain pan and loosen bolts
   Place the drain pan directly beneath the transmission pan. Beginning at one rear corner, loosen all pan bolts by approximately 2-3 turns using a socket wrench. Do not remove any bolts completely yet. Work around the entire perimeter to break the gasket seal evenly.
4. 4

   Drain transmission fluid
   Starting at the rear of the transmission pan, carefully remove the rear bolts while supporting the pan with one hand. Allow the rear of the pan to drop slightly so fluid begins draining into the catch pan. Gradually remove the remaining bolts, working from rear to front, while controlling the pan descent. Once fluid flow slows, remove all remaining bolts and lower the pan completely. Be prepared for approximately 4-5 quarts of fluid to drain.
5. 5

   Remove old filter
   Locate the transmission filter attached to the valve body inside the transmission case. It is typically held by 2-3 bolts or screws. Remove the fasteners and carefully pull the filter straight down, avoiding damage to the pickup tube. Some residual fluid will drain from the filter and valve body. Inspect the old filter for metal particles or excessive debris, which may indicate internal transmission wear.
6. 6

   Clean pan and magnet
   Thoroughly clean the inside of the transmission pan with shop rags, paying special attention to the magnetic drain plug if equipped. Remove all old gasket material from both the pan mating surface and the transmission case using a scraper or wire brush. Inspect the pan for cracks or damage. Clean the magnet and examine any metal particles collected—small amounts of fine material are normal, but large pieces or chunks indicate potential problems.
7. 7

   Install new filter
   Install the new pickup tube seal onto the filter inlet. Position the new filter onto the valve body, aligning it with the mounting holes. Install and hand-tighten the filter mounting bolts or screws. Tighten securely, but avoid overtightening as the valve body is aluminum and can strip easily. Ensure the filter is seated properly and the pickup tube seal is in place.
8. 8

   Install new gasket and pan
   Position the new gasket onto the transmission pan, ensuring all bolt holes align correctly. Some gaskets may have adhesive backing; others may require a thin bead of gasket sealer in the corners only. Carefully lift the pan with gasket into position against the transmission case, ensuring the gasket does not shift. Start all pan bolts by hand to avoid cross-threading.
9. 9

   Tighten pan bolts
   Tighten the pan bolts in a crisscross pattern, working from the center outward. Tighten gradually in multiple passes to ensure even gasket compression. Final torque should be approximately 10-12 ft-lbs—snug but not excessively tight, as overtightening can distort the pan and cause leaks. If no torque wrench is available, tighten firmly by hand with a standard ratchet until the gasket is compressed evenly.
10. 10

    Lower vehicle
    Raise the vehicle slightly with the floor jack, remove the jack stands, and carefully lower the vehicle to the ground. Ensure the area under the vehicle is clear before lowering.
11. 11

    Add transmission fluid
    Locate the transmission dipstick tube, typically on the passenger side of the engine bay. Remove the dipstick and insert a long-neck funnel into the tube. Add 4 quarts of the appropriate automatic transmission fluid (Type A or Dexron compatible). Do not overfill at this stage as the transmission has not been running to circulate fluid.
12. 12

    Start engine and check level
    Start the engine and allow it to idle. With your foot on the brake, shift the transmission through all gear positions (P-R-N-D-2-1), pausing briefly in each gear. Return to Park. With the engine still running at idle, check the transmission fluid level on the dipstick. Add fluid as necessary to bring the level to the 'ADD' or lower mark on the dipstick. Do not fill to the 'FULL' mark until the transmission reaches operating temperature.
13. 13

    Road test and final level check
    Drive the vehicle for 5-10 minutes to allow the transmission to reach normal operating temperature (approximately 160-180°F). Park on level ground with the engine running and transmission in Park. Recheck the fluid level with the dipstick and add fluid as needed to bring the level to the 'FULL' mark. Check underneath the vehicle for any leaks around the pan gasket.

Reassembly

1. Ensure all pan bolts are tightened evenly in a crisscross pattern to prevent gasket leakage
2. Dispose of used transmission fluid properly at a recycling center or auto parts store
3. Record the service date and mileage for maintenance tracking

Verification

• Check that transmission fluid level reads 'FULL' on dipstick with engine at operating temperature and running in Park
• Verify no fluid leaks are present around transmission pan gasket after road test
• Confirm smooth transmission operation through all gear ranges with no slipping or delayed engagement
• Inspect ground under vehicle after overnight parking to ensure no delayed leakage has developed

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