This procedure replaces the rear main crankshaft seal on a 2015-2020 Ford F-150 with the 3.5L EcoBoost V6 engine, requiring transmission removal to access the seal housing at the rear of the engine block.

Warnings

Tools required

Parts

• Rear main crankshaft seal × 1 — Use OEM Ford specification
• Rear main seal housing gasket × 1 — Use OEM Ford specification
• Engine oil drain plug crush washer × 1 — Use OEM specification
• Transmission fluid × 1 — Motorcraft MERCON LV
• RTV silicone sealant (if required) × 1 — Motorcraft TA-31

Fluids

• Motorcraft 0W-20 Full Synthetic — 6 qt
• Motorcraft MERCON LV ATF — 11 qt

Preparation

1. Park vehicle on level surface and apply parking brake firmly
2. Disconnect negative battery cable and wait 10 minutes for airbag system discharge
3. Raise vehicle to comfortable working height and support on jack stands at frame rails
4. Remove skid plates or under-vehicle protective panels if equipped
5. Drain engine oil completely and install drain plug with new crush washer
6. Allow transmission to cool if vehicle was recently driven

Procedure

1. 1

   Remove driveshaft
   Mark driveshaft flange-to-differential pinion flange orientation with paint or marker. Remove four driveshaft flange bolts. Support driveshaft and slide rearward to separate from transmission output shaft. Cap transmission extension housing to prevent fluid loss.
2. 2

   Disconnect transmission electrical connections and shift linkage
   Disconnect transmission wiring harness connectors at transmission body. Label each connector for reinstallation reference. Disconnect shift cable from transmission shift lever and remove cable bracket. On column shift models, disconnect column linkage.
3. 3

   Remove transmission cooler lines and exhaust components
   Disconnect transmission cooler lines at transmission using line disconnect tool. Cap lines to prevent contamination. Remove exhaust system from catalytic converters rearward or drop exhaust at H-pipe connection to provide clearance for transmission removal. Support exhaust with wire.
   ⚠Transmission fluid may drain from cooler lines. Have drain pan ready.
4. 4

   Support transmission and remove crossmember
   Position transmission jack under transmission pan with proper adapter or wood block to distribute load. Raise jack slightly to support transmission weight. Remove transmission crossmember mounting bolts and lower crossmember away from vehicle.
   Torque spec

   Mounting Bolts31 Nm (23 lb-ft)
5. 5

   Remove starter motor
   Disconnect starter electrical connections (both main power cable and trigger wire). Remove starter mounting bolts and extract starter motor from bellhousing. This provides access to lower transmission-to-engine bolts.
6. 6

   Remove transmission-to-engine bolts
   Remove all transmission-to-engine bellhousing bolts. On 3.5L EcoBoost applications, there are typically 6-8 bolts of varying lengths around the bellhousing perimeter. Note bolt locations and lengths for proper reinstallation. Ensure transmission is fully supported on jack before removing final bolts.
   Torque spec

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

   Separate and lower transmission
   Carefully pull transmission rearward ensuring torque converter remains fully seated in transmission (moves with transmission, not with engine). Once input shaft clears engine, carefully lower transmission on jack and remove from under vehicle. Place torque converter retention strap or wire to prevent it from falling out during service.
   ⚠️Transmission weighs over 200 lbs. Ensure transmission jack is secure and use assistance. Keep body clear of transmission during removal.
8. 8

   Remove flexplate
   Install flexplate holding tool or use large pry bar through starter opening to prevent crankshaft rotation. Remove all flexplate-to-crankshaft bolts. Note alignment dowel position if present. Carefully remove flexplate from crankshaft, noting any shims or spacers behind it.
   ℹ️Inspect flexplate for cracks around bolt holes or ring gear damage. Replace if any damage is found.
   Torque spec

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

   Remove rear main seal housing
   Remove all rear main seal housing bolts in a crisscross pattern. The housing is retained by multiple small bolts around its perimeter. Carefully pry housing away from engine block using plastic pry tools at designated pry points. Remove housing and old gasket material from engine block.
   ⚠Do not damage sealing surface on engine block. Aluminum is soft and scratches easily.
   Torque spec

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

    Remove and inspect old seal
    Using seal puller or pick tool, carefully extract old rear main seal from housing. Inspect seal housing bore for scratches, gouges, or damage. Inspect crankshaft seal surface for grooves, scoring, or damage. If crankshaft is damaged, replacement or machining may be required.
11. 11

    Clean all sealing surfaces
    Thoroughly clean rear main seal housing and engine block mating surfaces. Remove all old gasket material and RTV sealant using plastic scraper. Clean with brake cleaner and lint-free cloth. Ensure seal bore in housing is clean and free of debris. Clean crankshaft flange surface with solvent.
12. 12

    Install new rear main seal
    Lightly lubricate new seal lip with clean engine oil. Using proper seal installation tool or appropriately sized driver, install new seal into housing bore. Ensure seal is driven in squarely and seats fully to proper depth. Seal lip should face toward engine (spring side toward transmission). Verify seal is seated evenly around entire circumference.
    ⚠Do not damage seal lip during installation. Never use hammer directly on seal. Use proper installation tool to prevent cocking or damage.
13. 13

    Install seal housing with new gasket
    Install new gasket on engine block (some applications use RTV sealant instead - verify with FSM). Apply small bead of RTV sealant at engine block-to-oil pan junction points if specified. Position seal housing onto engine block, aligning dowel pins. Install all housing bolts finger-tight, then torque in crisscross pattern to specification.
    ℹ️If using RTV sealant, allow 15-30 minutes cure time before installing flexplate and transmission per manufacturer specifications.
    Torque spec

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

    Install flexplate
    Clean flexplate and crankshaft flange surfaces thoroughly. Install any shims or spacers removed during disassembly. Position flexplate onto crankshaft flange, aligning dowel pin if equipped. Install flexplate bolts and tighten in star pattern to specification. Use flexplate holding tool to prevent rotation during torque procedure.
    ℹ️Torque flexplate bolts in multiple passes using star pattern: 30 lb-ft, 50 lb-ft, then final 63 lb-ft.
    Torque spec

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

    Reinstall transmission
    Verify torque converter is fully seated in transmission pump (should be recessed approximately 1/2 inch from bellhousing face). Lubricate transmission input shaft and front pump seal with ATF. Raise transmission on jack and align with engine. Carefully slide transmission forward, ensuring torque converter hub engages crankshaft and transmission input shaft enters pilot bearing. Install all transmission-to-engine bolts and torque to specification.
    ⚠Do not use transmission-to-engine bolts to draw transmission to engine. Transmission should slide forward with moderate effort. If binding occurs, lower and realign.
    Torque spec

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

Reassembly

1. Install starter motor and torque mounting bolts to specification
2. Install transmission crossmember and torque mounting bolts to specification
3. Remove transmission jack once crossmember is secured
4. Reconnect transmission cooler lines ensuring proper seating of quick-connect fittings
5. Reinstall driveshaft aligning marks made during disassembly, torque flange bolts evenly
6. Reconnect all transmission electrical connectors and shift linkage in reverse order of removal
7. Reinstall exhaust system components and verify all hangers are properly seated
8. Reinstall skid plates or under-vehicle panels if equipped
9. Fill engine with proper quantity and specification of engine oil (6 quarts Motorcraft 0W-20)
10. Check transmission fluid level and add MERCON LV ATF as needed to reach proper level on dipstick with engine running and transmission at operating temperature

Verification

• Start engine and verify no oil leaks from rear main seal area while engine idles
• Check transmission for proper engagement in all gear ranges
• Test drive vehicle and verify smooth transmission operation and no vibration from driveline
• After test drive, re-inspect rear main seal area and transmission pan for any fluid leaks
• Recheck engine oil and transmission fluid levels after vehicle reaches operating temperature
• Verify no trouble codes stored in PCM or TCM related to transmission operation

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