drivetrain

Differential Pinion Seal

for 2018 Ford F-150 3.5L V6 EcoBoost · RWD

Editorial review:Chris Hackleman — Master Technician · 20+ years · Jeff Moore — Master Mechanic · 20+ years

Difficulty

Moderate

Time

2.4 h

Tools

Steps

✓Expert-verified. Personally reviewed and approved by OLP's master technicians (Chris Hackleman & Jeff Moore — 20+ years each). Always follow the vehicle's factory service information and torque specs.

This procedure covers removal and replacement of the rear differential pinion seal on a 2015-2020 Ford F-150 with 3.5L EcoBoost engine and rear-wheel drive configuration.

Warnings

⚠Vehicle must be safely supported on jack stands. Never work under a vehicle supported only by a floor jack.

⚠Gear oil may be hot if vehicle was recently driven. Allow adequate cooling time.

ℹ️Pinion bearing preload must be maintained during this procedure. Recording and matching the original pinion nut torque is critical to prevent bearing damage or noise.

⚠If pinion nut torque cannot be achieved during reinstallation, differential disassembly and bearing replacement may be required.

Tools required

Floor jack and jack standsEssential

Torque wrench (ft-lb range)Essential

1/2 inch drive socket setEssential

Paint marker or chalkEssential

Inch-pound torque wrenchEssential

Pinion flange holding tool or large channel locksEssential

Seal puller or pry barEssential

Seal installation driver or appropriate socketEssential

Catch pan for gear oilEssential

Wire brush

Dead blow hammer

Brake cleaner

As an Amazon Associate and Autel/ANCEL partner, OLP earns from qualifying purchases — how we link. This never changes the specs we publish.

Parts

Pinion seal × 1 — Use OEM specification
Pinion nut (recommended) × 1 — Use OEM specification
Rear differential gasket or RTV sealant × 1 — Motorcraft TA-357 or equivalent

As an Amazon Associate and Autel/ANCEL partner, OLP earns from qualifying purchases — how we link. This never changes the specs we publish.

Fluids

Motorcraft 75W-140 Synthetic Gear Oil — 2 qt

Preparation

Park vehicle on level surface and engage parking brake
Chock front wheels securely
Raise rear of vehicle and support with jack stands at frame rails
Allow differential to cool if vehicle was recently operated
Place catch pan under differential

Procedure

1
Mark driveshaft alignment
Use paint marker or chalk to mark the relationship between the rear driveshaft and the pinion flange. This ensures proper balance during reassembly and prevents potential vibration issues.
2
Remove driveshaft
Remove the four U-joint strap bolts at the pinion flange. Support the driveshaft and carefully lower it away from the differential. Secure the driveshaft to the frame or suspend with wire to prevent damage to the center bearing or CV joint.
Torque spec
Driveshaft U-Joint Straps20 Nm (15 lb-ft)
3
Drain differential fluid
Position catch pan directly under the differential cover. Remove all differential cover bolts and carefully pry the cover away from the housing. Allow all gear oil to drain completely. Inspect drained fluid for metal particles or excessive debris which may indicate internal damage.
⚠Gear oil will flow out quickly once cover is removed. Ensure catch pan has adequate capacity.
Torque spec
Differential Cover Bolts35 Nm (26 lb-ft)
4
Mark pinion rotating torque
Using an inch-pound torque wrench with a socket on the pinion nut, rotate the pinion flange through several revolutions and record the rotational torque required. This measurement is critical for maintaining proper pinion bearing preload. Typical values range from 16-29 inch-pounds for used bearings.
5
Mark and remove pinion nut
Mark the position of the pinion nut relative to the pinion shaft threads using paint marker. This provides a reference for reinstallation depth. Hold the pinion flange with a holding tool or large channel locks, then remove the pinion nut. Keep the nut if it will be reused, though a new nut is recommended.
6
Remove pinion flange
The pinion flange should pull off by hand once the nut is removed. If stuck, use a puller or carefully tap the flange with a dead blow hammer while supporting it to prevent dropping. Note the orientation and any alignment marks.
7
Remove old pinion seal
Use a seal puller or carefully pry out the old pinion seal from the differential housing. Take care not to damage the seal bore surface in the housing. Clean the seal bore thoroughly with brake cleaner and inspect for any scoring or damage that could cause the new seal to leak.
8
Install new pinion seal
Lightly coat the outer edge of the new seal with gear oil. Position the seal squarely in the bore with the seal lip facing inward toward the differential. Using a seal driver or appropriately sized socket, carefully tap the seal into place until it is flush with the housing face. Ensure the seal is not cocked or damaged during installation.
9
Reinstall pinion flange
Lightly coat the pinion seal contact surface on the flange with clean gear oil. Slide the pinion flange onto the pinion shaft in the original orientation. Ensure the flange seats fully onto the shaft.
10
Install and torque pinion nut
Thread the pinion nut (new or original) onto the pinion shaft. Hold the flange and tighten the nut gradually. Tighten to the marked position noted during disassembly, then check rotating torque with an inch-pound torque wrench. Continue tightening in small increments until the rotational torque matches the value recorded in step 4. Do not exceed 3 additional inch-pounds above the original value.
⚠️Over-tightening the pinion nut will collapse the pinion bearing spacer and ruin the bearing preload. If proper preload cannot be achieved, stop and consult a professional or disassemble for bearing replacement.
11
Clean and prepare differential cover
Remove all old gasket material from both the differential housing and cover using a scraper and wire brush. Clean both surfaces thoroughly with brake cleaner. If using a gasket, ensure surfaces are completely dry. If using RTV sealant, apply a continuous 1/8 inch bead to the cover sealing surface.
12
Reinstall differential cover
Position the cover with gasket or RTV onto the differential housing. Install all cover bolts hand-tight, then torque in a crisscross pattern to ensure even sealing and prevent warping.
Torque spec
Differential Cover Bolts35 Nm (26 lb-ft)
13
Refill differential
Remove the differential fill plug on the front of the housing. Using a fluid pump or funnel with hose, add Motorcraft 75W-140 Synthetic Gear Oil until fluid reaches the bottom of the fill hole. Install and tighten the fill plug. Total capacity is approximately 2 quarts.
14
Reinstall driveshaft
Align the marks made during disassembly and position the driveshaft onto the pinion flange. Install the four U-joint strap bolts and tighten evenly in a crisscross pattern to prevent binding.
Torque spec
Driveshaft U-Joint Straps20 Nm (15 lb-ft)