Transmission Flush

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

Tools required

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

1. Park vehicle on level surface and apply parking brake firmly
2. Place wheel chocks behind rear wheels
3. Allow transmission to cool completely if vehicle was recently driven
4. Raise front of vehicle with floor jack and support securely on jack stands at frame rails
5. Verify vehicle is stable before working underneath
6. Position drain pan under transmission oil pan

Procedure

1. 1

   Drain transmission fluid
   Locate 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.
2. 2

   Remove transmission oil pan
   Once 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.
3. 3

   Clean transmission pan
   Thoroughly 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.
4. 4

   Remove old transmission filter
   Locate 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.
5. 5

   Install new transmission filter
   Position 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.
6. 6

   Install new pan gasket and pan
   Position 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.
7. 7

   Torque transmission pan bolts
   Tighten 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.
8. 8

   Add initial transmission fluid
   Lower 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.
9. 9

   Start engine and circulate fluid
   Start 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.
10. 10

    Check and adjust fluid level
    With 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.
11. 11

    Perform final fluid level check
    Drive 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.
12. 12

    Inspect for leaks
    With 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

1. Ensure all tools and materials are removed from under the vehicle before lowering
2. Dispose of used transmission fluid properly at a recycling center or auto parts store
3. 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

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