Rear Main Seal

This procedure covers removal and replacement of the rear main crankshaft seal on a 2015-2020 Ford F-150 with 5.0L Coyote V8 engine, requiring transmission removal to access the seal housing.

Warnings

Tools required

Parts

• Rear main crankshaft seal × 1 — Ford FL3Z-6701-A or equivalent
• Rear main seal housing gasket or RTV sealant × 1 — Motorcraft RTV or OEM gasket
• Transmission rear seal (if leaking) × 1 — Use OEM specification
• Oil drain plug crush washer × 1 — Ford W710166-S300
• Flexplate or flywheel bolts if TTY type × 8 — Check service manual for TTY designation
• Oil pan gasket (rear section if disturbed) × 1 — Use OEM specification

Fluids

• Motorcraft 0W-20 Full Synthetic — 7.5 qt
• Motorcraft MERCON LV ATF — 1 qt

Preparation

1. Park vehicle on level ground and engage parking brake. Chock front wheels.
2. Disconnect negative battery cable to prevent electrical shorts.
3. Allow engine and transmission to cool completely (minimum 2 hours after operation).
4. Raise vehicle and support securely on jack stands at frame contact points.
5. Remove engine under-cover/skid plate if equipped.
6. Drain engine oil completely and remove oil filter. Install drain plug with new crush washer.
7. Support engine from above using engine support bar or hoist with load leveler.
8. Mark driveshaft-to-rear differential flange position with paint or marker for proper alignment during reinstallation.

Procedure

1. 1

   Remove exhaust components
   Disconnect exhaust system at manifold flanges or catalytic converter connection points to allow clearance for transmission removal. Support exhaust with wire or stands to prevent damage to hangers. On dual exhaust systems, both sides may need disconnection depending on transmission crossmember clearance.
2. 2

   Disconnect driveshaft
   Remove the four bolts securing the rear driveshaft to the differential flange. Use your alignment marks to note orientation. Lower driveshaft and slide it rearward to disengage from transmission output shaft. Plug transmission output shaft with a clean rag or plug to prevent fluid loss and contamination.
   ⚠Support driveshaft weight to prevent damage to universal joints during removal.
3. 3

   Disconnect transmission electrical and cooler lines
   Disconnect all electrical connectors from transmission including range sensor, solenoid body connector, and vehicle speed sensor. Label connectors if needed. Disconnect transmission cooler lines at transmission using line disconnect tools. Cap or plug lines to prevent fluid loss. Remove dipstick tube mounting bolt and remove tube from transmission.
   ⚠Have a drain pan ready as approximately 1 quart of ATF will drain from cooler line connections.
   Torque spec

   Electrical Connector Bolts8 Nm (6 lb-ft)
4. 4

   Remove transmission crossmember and support
   Place transmission jack under transmission pan with wood block to distribute load. Secure transmission to jack with safety chain or strap. Remove transmission crossmember mounting bolts (typically 4-6 bolts). Lower transmission jack slightly to relieve tension and remove crossmember. Do not lower transmission excessively at this point.
   Torque spec

   Mounting Bolts60 Nm (44 lb-ft)
5. 5

   Disconnect starter and remove
   Disconnect starter motor electrical connections (main power cable and trigger wire). Remove starter mounting bolts and remove starter motor from bellhousing. This provides access to lower bellhousing bolts and prevents damage during transmission removal.
   Torque spec

   Mounting Bolts60 Nm (44 lb-ft)
6. 6

   Remove bellhousing inspection cover and torque converter/flexplate bolts
   Remove bellhousing dust cover or inspection plate. For automatic transmission, rotate crankshaft using 22mm socket on crankshaft pulley bolt to access all torque converter-to-flexplate bolts (typically 4-6 bolts) through inspection opening. Remove all converter mounting bolts. For manual transmission, note flywheel orientation and use flywheel holding tool, then remove all flywheel bolts in reverse star pattern.
   ⚠Mark flexplate/flywheel position relative to crankshaft before removal to maintain engine balance.
   Torque spec

   Cover Bolts20 Nm (15 lb-ft)
7. 7

   Remove transmission-to-engine bolts and separate transmission
   Remove all transmission-to-engine bellhousing bolts (typically 6-8 bolts of varying lengths). Note bolt locations as they are different lengths. Ensure transmission is securely supported on transmission jack. Carefully slide transmission rearward away from engine, keeping it level. Guide torque converter to prevent it from sliding forward. Lower transmission and remove from under vehicle.
   ⚠️Transmission must remain level during removal to prevent it from binding on input shaft or dowel pins. Have assistant guide transmission if possible.
   Torque spec

   Transmission-to-Engine Bolts55 Nm (41 lb-ft)
8. 8

   Remove flexplate or flywheel
   Use flywheel holding tool to prevent crankshaft rotation. Remove all flexplate bolts (automatic) or flywheel bolts (manual) in a star pattern. Remove flexplate/flywheel from crankshaft flange. Inspect flexplate ring gear for damage or cracks. For manual transmission, inspect clutch and pressure plate while accessible.
   ℹ️Flexplate/flywheel bolts are often torque-to-yield and must be replaced. Consult service manual to confirm.
   Torque spec

   Flexplate Bolts85 Nm (63 lb-ft)

   Flywheel Bolts95 Nm (70 lb-ft)
9. 9

   Remove rear main seal housing if applicable
   On Coyote engines, the rear main seal may be housed in a separate aluminum housing bolted to the block. If present, remove all housing bolts in a crisscross pattern. Carefully pry housing from engine block using plastic pry tools at designated pry points. Remove and discard old gasket or RTV sealant. If seal is pressed directly into block, skip housing removal and proceed to seal extraction.
   ⚠Do not damage aluminum housing or engine block mating surfaces during removal.
   Torque spec

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

    Remove old rear main seal
    Using seal removal tool or carefully with a pry bar, extract old rear main seal from housing or block bore. Work around seal perimeter evenly to prevent cocking. If seal is stubborn, drill small hole in seal face and use slide hammer with screw attachment. Inspect crankshaft sealing surface for grooves, scratches, or damage. Minor imperfections can be polished with 600-grit sandpaper; deep grooves require crankshaft replacement or repair sleeve.
    ⚠Avoid damaging crankshaft sealing surface during seal removal. Do not use sharp tools directly against crankshaft.
11. 11

    Clean all mating surfaces
    Thoroughly clean rear main seal housing bore and engine block mating surfaces using brake cleaner and plastic scraper. Remove all old RTV sealant, gasket material, and oil residue. Clean crankshaft flange and sealing surface with brake cleaner and lint-free cloth. Use wire brush to clean flexplate/flywheel mounting bolt holes in crankshaft. Ensure all surfaces are completely clean and dry before installation.
    Torque spec

    Gasket Surface Bolts26 Nm (19 lb-ft)
12. 12

    Install new rear main seal
    Lightly lubricate new rear main seal lip with clean engine oil. Position seal with lip facing toward engine (spring side toward rear of engine). Using rear main seal installation tool or appropriately sized large socket matching seal OD, carefully drive seal squarely into housing or block bore. Tap evenly around perimeter to ensure seal seats fully and remains square. Seal should be flush or slightly recessed per manufacturer specification (typically 0-1mm below surface).
    ⚠Do not cock seal during installation. An improperly seated seal will leak immediately.
13. 13

    Reinstall rear main seal housing if applicable
    If engine uses separate seal housing, apply thin bead of Motorcraft RTV sealant to engine block mating surface or install new gasket per manufacturer instructions. Position housing over crankshaft and align dowel pins. Install all housing bolts hand-tight, then torque in crisscross pattern to specification. Allow RTV to cure per manufacturer instructions (typically 30 minutes) before adding oil.
    ℹ️Some applications use a dry gasket with no RTV. Consult service manual for correct sealing method.
    Torque spec

    Rear Main Seal Housing12 Nm (9 lb-ft)

    Gasket Bolts25 Nm (19 lb-ft)
14. 14

    Reinstall flexplate or flywheel
    Clean crankshaft flange and flexplate/flywheel mating surfaces with brake cleaner. Align flexplate/flywheel to crankshaft using alignment marks made during disassembly. Install new flexplate/flywheel bolts if TTY type, or clean and apply threadlocker to reusable bolts. Hand-start all bolts, then torque in star pattern to specification. Use flywheel holding tool to prevent rotation during tightening.
    ⚠Improper flexplate/flywheel balance will cause severe vibration. Ensure alignment marks are matched correctly.
    Torque spec

    Flexplate Bolts85 Nm (63 lb-ft)

    Flywheel Bolts95 Nm (70 lb-ft)
15. 15

    Reinstall transmission
    Position transmission on transmission jack and raise into position. For automatic transmission, ensure torque converter is fully seated in pump (should have 3 distinct clicks when rotated and pushed). Align transmission with engine dowel pins and carefully slide forward. Install all bellhousing bolts in correct locations and torque to specification. Install torque converter-to-flexplate bolts through inspection opening, rotating crankshaft to access each bolt. Reinstall starter motor and bellhousing dust cover. Reinstall transmission crossmember and torque mounting bolts. Remove transmission jack.
    ⚠Do not allow transmission to hang on input shaft. Use jack to support full weight until all bolts are installed.
    Torque spec

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

    Flexplate Bolts85 Nm (63 lb-ft)

    Mounting Bolts60 Nm (44 lb-ft)

    Cover Bolts20 Nm (15 lb-ft)

Reassembly

1. Reconnect transmission electrical connectors and cooler lines. Torque all electrical connector bolts to specification.
2. Reconnect driveshaft to rear differential flange, aligning marks made during disassembly. Torque all bolts evenly.
3. Reinstall exhaust connections and torque to specification with new gaskets if required.
4. Reinstall transmission dipstick tube if removed.
5. Refill engine with 7.5 quarts Motorcraft 0W-20 full synthetic oil and install new oil filter.
6. Add approximately 1 quart of Motorcraft MERCON LV ATF to transmission to replace fluid lost during cooler line disconnection.
7. Reinstall engine under-cover or skid plate if equipped.
8. Reconnect negative battery cable.
9. Lower vehicle from jack stands.

Verification

• Start engine and allow to idle. Monitor for oil leaks around rear main seal area for 5 minutes.
• Check engine oil level on dipstick and add if necessary to bring to full mark.
• Check transmission fluid level with engine at operating temperature and transmission in Park. Add fluid as needed.
• With vehicle on level ground and parking brake applied, shift transmission through all gears to verify proper operation.
• Test drive vehicle and verify no unusual vibrations, which could indicate flexplate/flywheel imbalance.
• After test drive, recheck for oil leaks around rear main seal, oil pan, and transmission areas.
• Recheck all fluid levels after vehicle has sat overnight. Monitor for leaks over next 100 miles of operation.

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