transmission
Transmission Flush
for 1970 AMC Rebel Machine 390ci V8 · RWD
Difficulty
Moderate
Time
2.5 h
Tools
13
Steps
12
🤖AI-generated, not yet human-verified. This walkthrough was produced by AI and may contain errors. Treat it as a guide, cross-check every step and torque value against the manufacturer's service manual, and stop if anything looks unsafe. This is a moderate-risk job — take extra care.
Complete flush and replacement of automatic transmission fluid and filter, removing old contaminated fluid and replacing with fresh ATF to maintain transmission performance and longevity.
Warnings
⚠️Transmission fluid can exceed 200°F during operation. Allow transmission to cool completely before starting work, minimum 2 hours after engine shutdown.
⚠When removing the transmission pan, fluid will drain quickly. Position drain pan carefully to avoid spills.
⚠Never run the engine with low transmission fluid level as this will cause immediate and severe transmission damage.
ℹ️The 1970 Rebel Machine uses a Borg-Warner automatic transmission. Verify your specific transmission type before beginning work.
Tools required
Floor jackEssential
Jack stands (4-ton minimum)Essential
Wheel chocksEssential
Drain pan (minimum 8 quart capacity)Essential
Transmission fluid pump or funnel with long tubeEssential
3/8 inch drive socket setEssential
Torque wrenchEssential
Gasket scraper or plastic scraper
Clean lint-free ragsEssential
Rubber mallet
Flashlight or work lightEssential
Filter wrench or large pliers
Degreaser spray
Parts
- Automatic transmission filter × 1 — Use OEM specification for Borg-Warner automatic
- Transmission oil pan gasket × 1 — Use OEM specification
- Transmission pan bolts (if damaged) × 1 — Use OEM specification
Fluids
- DEXRON automatic transmission fluid — 12 qt
Preparation
- Park vehicle on level surface and apply parking brake firmly
- Place wheel chocks behind rear wheels
- Allow transmission to cool completely if vehicle was recently driven
- Raise front of vehicle with floor jack and support securely on jack stands at frame rails
- Verify vehicle is stable before working underneath
- Position drain pan under transmission oil pan
Procedure
- 1Drain transmission fluidLocate the transmission oil pan at the bottom of the transmission. Loosen all pan bolts approximately 2-3 turns, but do not remove completely. Starting at the rear of the pan, carefully loosen the rear bolts more than the front to allow the pan to tilt and drain fluid gradually into the drain pan. Once fluid flow slows significantly, remove all bolts and carefully lower the pan, allowing remaining fluid to drain.
- 2Remove transmission oil panOnce fluid has drained, fully remove the transmission oil pan. If pan is stuck to the transmission case, gently tap with a rubber mallet to break the gasket seal. Be careful not to bend the pan flange. Inspect the pan interior for metal shavings or debris which may indicate internal transmission wear.
- 3Clean transmission panThoroughly clean the transmission oil pan interior using degreaser and lint-free rags. Remove all old gasket material from the pan sealing surface using a gasket scraper, taking care not to gouge or damage the pan. Wipe clean and ensure no debris or gasket material remains. Clean the transmission case gasket sealing surface in the same manner.
- 4Remove old transmission filterLocate the transmission filter inside the transmission, typically held by 2-3 bolts or a clip mechanism. Remove the mounting bolts or release the clips and carefully pull the filter straight down. Some fluid will drain from the filter and valve body, so keep the drain pan positioned underneath. Inspect the old filter for excessive debris or metal particles.
- 5Install new transmission filterPosition the new transmission filter into place, aligning it with the mounting holes or clip locations. Ensure the filter pickup tube seal is properly seated. Install and tighten the filter mounting bolts finger-tight, then snug with a socket wrench. Do not overtighten as the filter housing can crack.
- 6Install new pan gasket and panPosition the new gasket on the transmission oil pan, ensuring all bolt holes align correctly. Some gaskets are adhesive-backed for easier installation. Carefully raise the pan into position against the transmission case, ensuring the gasket remains properly aligned. Start all pan bolts by hand to prevent cross-threading.
- 7Torque transmission pan boltsTighten the transmission pan bolts in a crisscross pattern, working from the center outward. Torque bolts to 10-12 ft-lbs in multiple passes to ensure even gasket compression and prevent leaks. Do not overtighten as this can distort the pan and cause leaks.
- 8Add initial transmission fluidLower the vehicle to the ground. Locate the transmission dipstick tube on the passenger side of the engine bay. Using a transmission fluid pump or long-necked funnel, add 6 quarts of DEXRON automatic transmission fluid through the dipstick tube. This is the approximate amount drained from the pan and filter.
- 9Start engine and circulate fluidStart the engine and allow it to idle. With your foot firmly on the brake pedal, shift the transmission through all gear positions (P-R-N-D-2-1), pausing 2-3 seconds in each position. Return the shifter to Park. This circulates new fluid through the transmission and torque converter.
- 10Check and adjust fluid levelWith the engine running at idle and transmission in Park, remove the dipstick and wipe it clean. Reinsert fully, then remove and check the fluid level. The level should be between the ADD and FULL marks on the cold side. Add fluid as needed in 1/2 quart increments, rechecking after each addition. Do not overfill.
- 11Perform final fluid level checkDrive the vehicle for 10-15 minutes to bring transmission fluid up to normal operating temperature (160-200°F). Park on level ground with engine running and transmission in Park. Check the dipstick again, and the fluid level should now read between the ADD and FULL marks on the hot side. Add fluid if necessary to bring to the proper level.
- 12Inspect for leaksWith the vehicle raised safely on jack stands, inspect the transmission pan gasket area for any signs of fluid leakage while the engine is running. Check all around the pan perimeter. If leaks are detected, shut off the engine, allow to cool, and re-torque pan bolts. If leaking persists, the pan may need to be removed and gasket reinstalled.
Reassembly
- Ensure all tools and materials are removed from under the vehicle before lowering
- Dispose of used transmission fluid properly at a recycling center or auto parts store
- Keep transmission dipstick easily accessible for regular fluid level checks
Verification
- Verify transmission fluid level is correct on the hot side of dipstick with engine at operating temperature
- Confirm no fluid leaks from transmission pan gasket after test drive
- Verify smooth transmission operation through all gear ranges with no slipping or delayed engagement
- Check that fluid on dipstick is bright red and clean, not dark or burnt smelling
- Monitor transmission operation over the next 100 miles and recheck fluid level