F-150 Rear Differential Fluid Change: Ford 8.8 & 9.75 Drain, Fill, Sealant and Cover Torque

No F-150 owner’s manual describes a rear-axle drain plug, the fluid and the amount Ford calls for changed between generations, and the right cover-bolt torque depends on which cover and which bolts you are holding. Here is the job end to end, with every number tied to the document it came from.

Which axle is under your F-150?

The F-150 rear axles in this guide are the Ford 8.8-inch and the 9.75-inch (ring-gear diameter). Ford’s owner’s manuals name both sizes in the 2004–2010 capacity tables (and in the 2011–2013 friction-modifier notes), and again from 2021, when the table gives each size its own capacity. Raptors use the 9.75. On 2021–2025 trucks, Ford’s Ford SSM 54194 (via NHTSA) identifies the 9.75 by minor feature code EGPAF in the vehicle’s build data, which a dealer can look up from the VIN.

Counting cover bolts is the quick check people use. Aftermarket makers sell the 8.8 cover as a 10-bolt (aFe lists its 10-bolt 8.8 cover for 1983–2014 F-150s) and the 9.75 as a 12-bolt (aFe lists its 9.75 cover for 1997–2021 F-150s). Treat the count as a clue, not proof. We could not find a Ford document that ties bolt count to axle size for every year, so on 2015-and-later trucks confirm with the build data or a parts counter before you buy a cover or a gasket.

Fluid type and capacity by model year

Ford changed both the oil and the amount over the years, so don’t carry one number across generations. These are the rear-axle entries from the Capacities and Specifications chapter of each year’s F-150 owner’s manual:

The 2016 manual’s maintenance text prints the spec as “WSS-M2C9Y2-A”, which is a misprint. The capacity tables from 2015 on all print WSS-M2C942-A.

Front axle (4x4). Ford’s capacity tables list the front differential separately. 2006–2016 trucks use Motorcraft SAE 80W-90 (XY-80W90-QL, WSP-M2C197-A). 2017-and-later trucks use the same 75W-85 as the rear, at 3.5 pt (1.7 L) in 2017 and 1.8 qt (1.7 L) from 2020; the 2024 Tremor’s Torsen front axle lists 1.6 qt (1.55 L). Most front differentials are serviced through their own plugs rather than by pulling a cover; this guide covers the rear.

Friction modifier: who needs it

• 2004–2017 limited-slip (Traction-Lok). The owner’s manuals call for 4 oz (118 ml) of Motorcraft Additive Friction Modifier XL-3 (EST-M2C118-A) on a complete refill of a Traction-Lok axle. The 2004 manual names the FEHP modifier XL-7.
• How it counts toward the fill. Ford’s Motorcraft axle lubricant chart (2004–2014) says the oil refill volume does not include the modifier, that the modifier goes in first, and not to overfill above the volumes shown. Ford Racing’s 8.8 sheet adds the 4 oz on top of 5–5.25 pt of oil. The wording leaves room for doubt, so add the modifier first and finish by checking the level at the fill hole.
• Electronic locking differential. The same Motorcraft chart marks F-150 locker axles “N/A” for friction modifier.
• 2018–2024 rear axles. We found no rear-axle friction-modifier instruction in these manuals. The 2022 and 2024 XL-3 notes sit under the front Torsen/Tremor axle. If you have a limited-slip rear on a late truck, ask a dealer before you add anything.

When to change it

Ford’s guidance is looser than most people expect. The 2004–2014 manuals call the synthetic-filled rear axle “lubricated for life”: it isn’t checked or changed unless a leak is suspected, service is required, or the axle has been under water. Most manuals from 2011 to 2023 also list a rear-axle fluid change at 150,000 miles (240,000 km) in the maintenance schedule, while the Exceptions text in the 2018–2024 manuals says changes are not required unless there is a leak or submersion. The 2024 manual drops the 150,000-mile line. Every year agrees on one rule: change the rear axle fluid any time the axle has been submerged in water.

Heavy towing tightens it. The 2017 manual says that during long periods of towing above 70°F (21°C), or at wide-open throttle above 45 mph for long periods, a rear axle filled with non-synthetic fluid should be changed every 30,000 mi (48,000 km). Filling with the 75W-85 synthetic lets you skip that and stay on the 150,000-mile interval. The 2013–2016 manuals print 3,000 miles in the same sentence, so check your own manual.

No drain plug? Your three options

No F-150 owner’s manual we checked describes a rear-axle drain plug. Ford Racing’s 8.8 ring-and-pinion procedure (Ford Racing M-4209-8.8 instruction sheet, written for the 1994–2012 Mustang) opens with “Remove the 10 differential housing cover bolts and drain the lubricant from the axle housing.” Ford Performance even sells a 9.75 cover that features a magnetic drain plug. That leaves three ways to get the old oil out:

If this is the first change on a high-mileage or towing truck, or the axle has been under water, pull the cover. A pump through the fill hole won’t let you see what’s at the bottom of the housing.

Tools and supplies

• Socket and ratchet for the cover bolts, and whatever fits your fill plug. Check that before you start.
• A drain pan wide enough to catch oil that comes off the whole lower edge of the cover.
• A plastic scraper or gasket scraper, brake cleaner and lint-free rags.
• Gear-oil-compatible RTV, a new gasket, or the cover’s O-ring (see the sealant section).
• Fluid to your model year’s spec, plus friction modifier if your axle needs it.
• A fluid pump or squeeze bottle. The fill hole is hard to reach from a funnel.
• A torque wrench whose range covers your figure. A 3/8-in drive wrench suits the 11–16 lb-ft aftermarket figures; see torque wrench sizes.
• Masking tape and a marker to label stud bolts and brackets as they come off.

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Step by step: drain by removing the cover

1. Park level and make it safe. Chock the wheels, and if you lift the truck, support it on jack stands. Let a hot axle cool before you open it.
2. Loosen the fill plug first. If the fill plug won’t come out, you don’t want to find that out with the axle empty.
3. Note every bracket. Photograph the cover. Before a bolt comes out, see whether it holds a brake-line retainer, an ABS-wire clip or a bracket, and tape-label those positions (see the next section).
4. Loosen from the bottom, keep the top in. aFe’s procedure removes the bottom seven of ten bolts and only loosens the top three. Mag-Hytec says to start at the bottom. Pry the lower edge carefully and let the oil run into the pan while the top bolts hold the cover. Pry at the edge rather than wedging a screwdriver into the sealing faces.
5. Remove the cover and look. With the oil out, check the gears and the bottom of the housing for metal flakes or chunks before you clean anything away.
6. Clean both faces until they are dry and oil-free. Ford Racing’s 8.8 sheet says the machined surfaces on both the housing and the cover must be “clean and free of oil” before new sealant goes on. Remove all old RTV and keep debris out of the housing.
7. Seal with a bead, gasket or O-ring as the cover requires (below).
8. Fit the cover and start every bolt by hand, with each stud bolt and bracket back in its original position.
9. Torque in a crisscross pattern to the figure for your cover and its bolts (table and diagram below).
10. Let the RTV cure before filling (Ford Racing: about an hour), then fill to the correct level and refit the plug.
11. Drive, then recheck. Look for wetness along the cover edge and at the fill plug after the first drive.

Callout: not every cover bolt is the same

• Ford’s own example. The Ford Performance M-4033-R (Ranger cover kit) instructions for a Ranger cover kit describe “differential housing cover stud bolts (2)”, removed with a deep-wall 10 mm socket, that carry the brake-line retainers. The cover goes back on with the 10 new bolts plus those two studs, and the plastic retainers press back onto the studs. Ford gives the same 20–25 lb-ft for the bolts and the studs on that kit.
• F-150 9.75. The aFe 46-70150 (9.75, 12-bolt) sheet says, “If applicable, remove the ABS wire from the studded bolts”, and to remove “any brackets fastened to the cover or cover bolts.” Its kit then supplies three brackets and three extra washers so the ABS wire rides under ordinary cover screws. The aFe 46-71320B (9.75) sheet starts with “Remove the brake line bracket by pulling the bolt out of the differential housing.”
• Girdle covers add a second size entirely. On a girdle cover the two load bolts that bear on the bearing caps are different fasteners from the perimeter bolts. Ford Performance M-4033-G2 (Mustang 8.8 girdle) tightens its 10 perimeter bolts to 20–25 lb-ft, its load bolts to only 5–10 lb-ft and its jam nuts to 25–30 lb-ft. The B&M 40298/41298 (9.75) instructions pair twelve 5/16-18 × 1 in cap screws with two 1/2-13 × 3-3/4 in load screws set to 5 ft-lb. Don’t run the perimeter torque on the load bolts.
• Aftermarket perimeter screws are uniform. aFe’s 8.8 and 9.75 kits, Mag-Hytec and B&M all supply 5/16-18 cover screws, one length per kit (girdle load screws aside). Don’t mix their screws with leftover factory bolts. Each torque figure belongs to the screws it ships with.

How to keep them straight: lay the bolts out on cardboard in the same ring as the cover, or push each through a labelled hole in it, and note which ones carry brackets. On reassembly, start the stud bolts first so the brackets end up where the lines were routed.

Sealant: RTV bead, gasket or O-ring

Cover bolt torque: match the number to the cover

A single “Ford 8.8 cover torque” doesn’t exist. The number depends on the cover material, the bolts and the maker. These are the published figures we could verify. Keep each one with the cover and hardware it belongs to:

Why the 8.8 figure comes from a Mustang sheet: Ford doesn’t print cover torque in the F-150 owner’s manual, and the F-150 workshop manual wasn’t accessible to us. The 8.8 is the same axle family, and the Ford Racing sheet is Ford’s own published figure for its steel and aluminum covers. If you have the F-150 workshop manual for your year, its figure takes priority.

Tightening sequence

Every maker we checked says to tighten in opposing pairs: aFe “X-pattern” and “crisscross”, Mag-Hytec “cross tight”, B&M “criss-cross”. None of them numbers the holes, so the order above is a valid crisscross, not a Ford sequence. The goal is to clamp the cover down evenly so a stamped cover doesn’t bow and the bead or gasket squeezes out evenly.

1. Start every bolt by hand, stud bolts and brackets in their original holes.
2. Snug the top bolt, then the one directly below it. Work around in opposite pairs until the cover sits flat and evenly on the bead.
3. Go round again in the same order to roughly half the final figure. This step is optional but helps with RTV, which squeezes out as it is clamped.
4. Final pass in the same order to the full torque for your cover.
5. Check pass: same order, wrench set to the final value. Any bolt that turns was not done; a bolt that clicks without moving is finished. Don’t go round a second time adding extra pull.

Refill and check the level

• 2004–2014 trucks: the owner’s manuals define the refill as filling “to 1/4-9/16 inch (6-14 mm) below the bottom of the filler hole with the vehicle on a level surface.”
• 2015–2024 trucks: the manuals give only a capacity (table above). Measure what you pour, then check the level at the hole.
• Ford Racing’s 8.8 sheet defines refill as “to the bottom of the fill hole with the axle at ride height” and tightens the filler plug to 22 lb-ft (30 N·m). That is the Mustang 8.8 figure; use your truck’s workshop manual if you have it.
• Aftermarket covers each have their own method. aFe fills through its top port until oil runs from the side port (about 4 qt on its 8.8 and 9.75 covers). Mag-Hytec fills through its dipstick opening to between the dipstick marks (about 4 qt on the 8.8, 4–5 qt on the 9.75) and says to drive at least 25 miles and recheck. B&M fills until oil just overflows the factory fill hole. aFe’s M12 × 1.25 drain plug with crush washer is 20 ft-lb (27 N·m). B&M’s plugs are 25–30 ft-lb with PTFE tape.
• Limited-slip: add the friction modifier first where your manual calls for it, then bring the oil up to the level.

Mistakes that cause leaks or damage

• Filling before the RTV has cured, or fitting the cover more than about 15 minutes after laying the bead.
• Leaving oil film or old RTV on either face. The new bead won’t bond to oil.
• Torquing around the cover in a circle instead of across it.
• Using Ford’s figure on aftermarket screws, or an aftermarket figure on factory bolts.
• Losing track of the stud bolts, so brake lines or ABS wiring end up loose or routed somewhere new.
• Using one capacity for every year. The 2021-and-later figures are much smaller.
• Skipping friction modifier on an older Traction-Lok axle, or adding it where Ford doesn’t call for it.

Frequently asked questions

Keep going

Sources

• Ford F-150 owner’s manuals, model years 2004–2008 and 2010–2024: Capacities and Specifications (rear and front axle fluid, capacity, friction modifier, 2004–2014 fill level), Scheduled Maintenance and its Exceptions (150,000-mile change, submersion rule, towing note). The 2009 manual was not available to us. Ford’s Motorcraft Axle Lubricants Quick Reference chart (v4.0, 2013) for locker and friction-modifier notes.
• Ford Racing M-4209-8.8: 8.8 Ring and Pinion Installation — cover-off drain, sealant bead and 15-minute/1-hour rule, 33/24 lb-ft cover bolts, 22 lb-ft fill plug.
• Ford Performance M-4033-R: Ranger Differential Cover Kit — brake-line stud bolts, 20–25 lb-ft.
• Ford Performance M-4033-G2: Axle Girdle Cover Kit 8.8 — perimeter vs load bolts, no silicone on gasket.
• Ford Special Service Message 54194 (via NHTSA) — 9.75 build code EGPAF on 2021–2025 F-150.
• aFe 46-71410A/B instructions (Ford 8.8 10-bolt) — fitment, screws, RTV, 15 ft-lb X-pattern, drain plug, fill.
• aFe 46-70150/46-70152 instructions (Ford 9.75) — fitment and sway-bar exclusion, studded bolts and brackets, reusable gasket, 11–14 ft-lb crisscross.
• aFe 46-71320B instructions (Ford 9.75) — brake-line bracket bolt.
• Mag-Hytec Ford 10-8.8 instructions — O-ring seal, 16 ft-lb cross-tight, capacity, friction modifier.
• Mag-Hytec Ford 12-9.75 instructions — 12 screws, 12–16/16 ft-lb, capacity.
• B&M 40298/41298 Ford 9.75 cover instructions (hosted by Rudy’s Diesel) — 15 ft-lb criss-cross, load screws, gasket or gear-oil-compatible RTV, plug torque.