This procedure involves removing the transmission to access and replace the rear main crankshaft seal on a 2021-2024 Ford F-150 with the 3.5L EcoBoost V6 engine.

Warnings

Tools required

Parts

• Rear main crankshaft seal × 1 — Use OEM Ford specification
• Rear main seal housing gasket × 1 — Use OEM specification
• Oil drain plug crush washer × 1 — Use OEM specification
• Transmission fluid × 1 — Motorcraft MERCON LV ATF
• Engine oil × 1 — Motorcraft 0W-20 Full Synthetic
• RTV silicone sealant × 1 — Motorcraft TA-357 or equivalent

Fluids

• Motorcraft 0W-20 Full Synthetic — 6 qt
• Motorcraft MERCON LV ATF — 13 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Disconnect negative battery cable and secure away from terminal
3. Raise vehicle and support securely on jack stands at frame contact points
4. Remove skid plates and underbody panels for access to transmission
5. Allow engine and transmission to cool completely if recently operated
6. Place drain pan under engine oil pan and drain engine oil completely
7. Place drain pan under transmission and remove transmission drain plug to drain fluid
8. Mark driveshaft-to-differential flange orientation for proper reinstallation

Procedure

1. 1

   Remove driveshaft
   Remove the four mounting bolts securing the driveshaft to the rear differential pinion flange. Support the driveshaft and carefully slide it rearward out of the transmission extension housing. Install a transmission plug or cap to prevent fluid leakage.
2. 2

   Disconnect transmission electrical connections
   Locate and disconnect all electrical connectors from the transmission including the transmission range sensor, speed sensors, and solenoid body connector. Remove any electrical connector mounting bolts and secure harnesses away from work area.
   Torque spec

   Electrical Connector Bolts8 Nm (6 lb-ft)
3. 3

   Remove transmission cooler lines and shift linkage
   Disconnect transmission cooler lines at the transmission using appropriate line disconnect tools. Cap all open fittings to prevent contamination. Disconnect the shift cable from the transmission range sensor lever and remove the cable bracket mounting bolts.
4. 4

   Remove starter motor
   Disconnect starter motor electrical connections. Remove starter mounting bolts and carefully extract the starter motor from the bell housing. This provides access to lower transmission-to-engine bolts.
   Torque spec

   Mounting Bolts55 Nm (40 lb-ft)
5. 5

   Support transmission and remove crossmember
   Position transmission jack under transmission oil pan with wood block to distribute load. Raise jack slightly to support transmission weight. Remove transmission mount-to-crossmember bolts, then remove crossmember-to-frame bolts. Lower and remove crossmember.
   Torque spec

   Mounting Bolts55 Nm (40 lb-ft)
6. 6

   Remove transmission-to-engine bolts
   Remove all transmission-to-engine bell housing bolts. There are typically 6-8 bolts of varying lengths around the perimeter. Note bolt locations and lengths for proper reinstallation. Ensure transmission is fully supported on transmission jack before removing final bolts.
   ⚠Keep transmission level and supported at all times to prevent damage to input shaft and torque converter.
   Torque spec

   Transmission-to-Engine Bolts55 Nm (41 lb-ft)
7. 7

   Separate and lower transmission
   Carefully pull transmission straight back away from engine, ensuring torque converter remains fully seated in transmission (does not pull out with flexplate). Lower transmission on jack and remove from under vehicle. Secure torque converter to prevent it from sliding out.
   ⚠️Transmission is extremely heavy. Use slow controlled movements and ensure jack is stable during lowering process.
8. 8

   Remove flexplate
   Install flexplate holding tool to prevent crankshaft rotation. Remove all flexplate-to-torque converter bolts if still attached. Remove flexplate-to-crankshaft bolts in a criss-cross pattern. Remove flexplate from crankshaft and inspect for cracks or damage.
   Torque spec

   Flexplate Bolts85 Nm (63 lb-ft)
9. 9

   Remove rear main seal housing
   Remove all bolts securing the rear main seal housing to the engine block. Carefully pry housing away from block using appropriate pry points (do not damage sealing surfaces). Remove housing and old gasket material. Inspect crankshaft sealing surface for grooves or damage.
   ⚠Do not scratch or gouge the aluminum sealing surfaces on the engine block or housing. Any damage will prevent proper seal.
   Torque spec

   Rear Main Seal Housing12 Nm (9 lb-ft)
10. 10

    Remove old rear main seal
    Use seal pick or small pry tool to carefully extract the old rear main seal from the housing. Clean the seal bore in the housing thoroughly with brake cleaner and lint-free cloth. Inspect bore for any damage or scoring that could affect new seal.
11. 11

    Install new rear main seal
    Lightly coat the outer diameter of the new seal with clean engine oil. Using the proper rear main seal installation tool, carefully drive the new seal squarely into the housing bore until it is fully seated and flush with the housing face. Ensure seal is not cocked or damaged during installation.
    ⚠Do not use a hammer directly on the seal. Always use the proper installation tool to prevent seal damage.
12. 12

    Clean and prepare mating surfaces
    Thoroughly clean the rear main seal housing mating surface and the engine block mating surface. Remove all old gasket material, RTV, oil residue, and debris using a plastic scraper. Wipe surfaces with brake cleaner and lint-free cloth. Surfaces must be completely clean and dry.
    ⚠Any oil, coolant, or debris on mating surfaces will prevent proper seal and cause immediate leakage.
13. 13

    Install rear main seal housing
    Install new housing gasket onto the housing. Apply small bead of RTV sealant at the oil pan-to-block corner joints if specified by manufacturer. Lightly oil the seal lip and carefully slide housing over crankshaft, ensuring seal lip is not damaged. Install all housing bolts and tighten in a criss-cross pattern to specified torque.
    Torque spec

    Rear Main Seal Housing12 Nm (9 lb-ft)
14. 14

    Reinstall flexplate
    Clean crankshaft flange and flexplate mating surfaces. Position flexplate onto crankshaft ensuring proper alignment with dowel pins. Install new flexplate bolts and tighten in star pattern to specified torque. Use flexplate holding tool to prevent rotation during tightening.
    ℹ️Flexplate bolts may be torque-to-yield (TTY). Use new bolts if required by manufacturer specification.
    Torque spec

    Flexplate Bolts85 Nm (63 lb-ft)
15. 15

    Reinstall transmission
    Position transmission on transmission jack and raise into position. Ensure torque converter is fully seated in transmission pump (should be recessed approximately 1 inch from bell housing face). Align transmission with engine and carefully slide forward onto dowel pins. Install all transmission-to-engine bolts and tighten to specified torque in a star pattern.
    Torque spec

    Transmission-to-Engine Bolts55 Nm (41 lb-ft)

Reassembly

1. Reinstall transmission crossmember and mount, torquing all fasteners to specification
2. Reinstall starter motor with proper torque on mounting bolts
3. Reconnect all transmission electrical connectors and secure harness clips
4. Reconnect transmission cooler lines and shift cable linkage
5. Reinstall driveshaft aligning marks made during disassembly, torque flange bolts properly
6. Install new oil drain plug crush washer and reinstall drain plug to specified torque
7. Reinstall all skid plates and underbody panels
8. Lower vehicle from jack stands

Verification

• Fill transmission with correct quantity and type of Motorcraft MERCON LV ATF through dipstick tube
• Fill engine with correct quantity of Motorcraft 0W-20 synthetic engine oil
• Start engine and check immediately for any oil leaks from rear main seal area
• With engine running and parking brake engaged, cycle transmission through all gear ranges
• Check transmission fluid level with engine at operating temperature and adjust as needed
• Road test vehicle and recheck for any oil leaks after test drive
• Verify no transmission slipping or abnormal operation
• After 50-100 miles, recheck engine oil and transmission fluid levels and inspect for any seepage

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