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Part #
Year
Manufacturer
Model
Condition
Drivetrain
Gear Ratio
Differential

Reman M300 Rear Axle Assembly

This remanufactured rear differential assembly is built for the 2017 Ford F450/F550 Super Duty in both 4X2 and 4X4 configurations. With the 2017 model year, Ford moved the F450 and F550 to the Dana M300 platform, a major break from the earlier S110 and S130 axles. You get the 4.5 inch axle tube, 11.8 inch ring gear, 1.64 inch minor diameter, and 41 spline shafts that define this generation.

The M300 is a full floating, drop out design that carries the heavy load ratings these trucks were built for. Pickup F450 variants carry a 9,650 lb rating, while Cab and Chassis F450/F550 units move up to 13,600 lb, and the F550 High Capacity Tow Package reaches 14,706 lb. Every unit we send out is remanufactured and ready to install, so you bolt in a rebuilt core rather than gamble on an unknown used housing.

Fitment, Ratios And Configuration

Fitment covers 2017 Ford F450 and F550 Super Duty trucks on the Dana M300 platform, which Ford carried forward through the 2022 model year. Because 2017 through 2022 share the same core M300 design, a correct 2017 unit will interchange within that range when the gear ratio, body style, and brake setup match your truck. Always confirm against your VIN and door label before ordering.

Gear ratios seen across the 2017 F450/F550 market include 4.10, 4.30, and 4.88, with 4.88 commonly tied to Cab and Chassis builds. Ratio matching is not optional. On a 4X4 truck a mismatched rear ratio against the front axle can cause serious drivetrain damage, so we verify the ratio tag and confirm it against the ratio you need before the axle ships.

Body style is the other critical detail. The Pickup and Cab and Chassis units share the same core M300 but differ in spring perch width, driveshaft end yoke, and GAWR paper rating. A Pickup rear axle is not compatible with a Cab and Chassis application and the reverse is also true. Tell us DRW status, Pickup or Cab and Chassis, ratio, and whether you have limited slip and ABS.

Specs That Define This Axle

The M300 rides on a 4.5 inch diameter axle tube with 14 differential cover bolts, a clean visual marker that separates it from the pre 2017 S110 and S130. The ring gear measures 11.8 inches, and the shafts run 41 splines with a 1.64 inch minor diameter, all built around genuine Dana and Spicer components.

The axle shafts are non equal in length, a detail that trips up a lot of buyers. The right rear shaft measures 39.450 inches, while the left rear shaft runs 40.950 inches, both at 41 splines. The Ford OEM left shaft HC3Z4234M covers F450 and F550 from 2017 through 2021 at that same 40.95 inch length.

ABS sensors on the M300 sit inboard near the differential rather than out at the wheel ends. The F450 and F550 also use a wide track housing with end extensions and different knuckles that open up clearance for a sharper turning radius. That wide track housing is specific to these platforms and will not swap with an F350 unit.

Why does this axle matter so much to Houston truck owners? The F450 and F550 are the backbone of commercial work across Texas, hauling for oilfield service, construction, equipment transport, and heavy towing. When the rear axle on one of these workhorses fails, the truck is parked and the job stops. A remanufactured M300 assembly gets you back to full payload and towing capacity quickly, with a rebuilt core that handles the loads these chassis cabs were engineered to carry day after day in the field.

A complete remanufactured assembly is also frequently the smarter path versus rebuilding a failed unit in your garage. Internal rebuilds on the M300 demand precise pinion bearing preload and gear mesh, and a backyard setup that is slightly off will howl and fail again. By starting with a professionally remanufactured drop out unit built to the correct ratio and configuration, you skip the guesswork, the special tools, and the repeat teardown that so often follows an improperly set up differential.

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Signs Your Rear Axle Is Failing

The most common warning is a whining or howling noise that tracks with vehicle speed rather than engine RPM, usually loudest during acceleration or deceleration above 20 to 30 mph. That sound typically points to worn pinion bearings or gear mesh that has drifted out of spec inside the differential.

A grinding or rumbling noise, especially while turning, often signals failing carrier bearings or damaged spider gears. A clicking sound in turns and a clunk when you get on or off the throttle are also classic M300 distress signals. Differential fluid leaking from the cover or pinion seal frequently accompanies these noises.

If the axle has suffered catastrophic internal failure, power simply will not reach the drive wheels and the truck will not move at all. Once you hear consistent gear noise or spot heavy, wet oil around the housing, it is time to plan a replacement before a roadside breakdown with a full load.

Before you order, inspect the axle you are removing and confirm the configuration you need. Look down both axle tubes for bends and examine the housing around the welds, spring perches, and suspension mounts for any cracking. On a working truck that has towed hard in Texas heat, a stressed housing is common. Pull your gear ratio tag, confirm DRW, and note whether your truck is a Pickup or Cab and Chassis so the replacement matches your exact application.

When your remanufactured M300 arrives, give it the same inspection discipline we use. Check the pinion yoke by grabbing it and trying to move it up, down, and side to side, there should be no noticeable play. Verify the ratio tag, confirm the 41 spline shafts and 11.8 inch ring gear match your platform, and check the differential cover and pinion seal for a clean, dry seal. These few minutes protect your install and your drivetrain.

Lubrication And Installation Notes

The F450 and F550 rear axle calls for Motorcraft SAE 75W-140 Synthetic Rear Axle Lubricant meeting Ford spec WSL M2C192-A, with a fluid capacity of 14.0 pints, roughly 6.6 liters. Using the correct synthetic lubricant protects the pinion and carrier bearings under the sustained heavy loads these trucks see, and keeps gear mesh temperatures in check during long hauls and heavy towing.

Ford design rear axles use a synthetic lubricant that is not meant to be changed on a routine interval. The exception is submersion. If the axle has been driven through water deep enough to reach the housing, the fluid should be drained and replaced to avoid contamination that destroys bearings. On a jobsite truck working flooded or muddy ground, this is worth checking after the fact.

Because the M300 is a full floating, drop out design, installation follows a predictable process when you have the right unit. Match the gear ratio to your front axle on 4X4 trucks, confirm the brake and ABS configuration, and torque the differential cover across all 14 bolts to spec with fresh sealant. A correctly set up remanufactured assembly restores factory payload and towing behavior from the first mile.

Frequently Asked Questions

What rear axle is in a 2017 Ford F450/F550?

The 2017 F450 and F550 use the Dana M300 rear axle, which replaced the earlier S110 and S130. It features a 4.5 inch tube, 14 cover bolts, an 11.8 inch ring gear, and 41 spline shafts built from genuine Dana and Spicer components.

What is the difference between the F450 and F550 rear axle?

Both run the Dana M300 core, but the ratings differ by configuration. The F450 Pickup carries a 9,650 lb rating, F450 and F550 Cab and Chassis units carry 13,600 lb, and the F550 High Capacity Tow Package reaches 14,706 lb, with differences in spring perch width, yoke, and GAWR.

What gear ratios are available on the 2017 F450/F550 rear axle?

Common ratios on the 2017 F450/F550 market are 4.10, 4.30, and 4.88. The 4.88 ratio is typically tied to Cab and Chassis builds. Pull your ratio tag and confirm the exact ratio before ordering, since a mismatch on a 4X4 can damage the drivetrain.

Is a 2017 F450 rear axle the same as a 2022 F450 rear axle?

The 2017 through 2022 F450 and F550 trucks share the same Dana M300 platform, so they are broadly cross compatible when the gear ratio, DRW status, body style, and brake and ABS configuration all match. Always verify against your VIN and door label before buying.

What are the signs that a 2017 F450/F550 rear axle needs to be replaced?

Watch for a whining or howling noise that changes with vehicle speed, a clunk on acceleration or deceleration, a clicking sound in turns, and gear oil leaks from the cover or pinion seal. Complete internal failure stops power from reaching the drive wheels.

Will a 2017 F450 Pickup rear axle fit an F450 Cab & Chassis?

No. Although both use the M300 core, the Pickup and Cab and Chassis units differ in spring perch width, driveshaft end yoke, and GAWR rating. A Pickup axle is not compatible with a Cab and Chassis truck, so specify your body style when ordering.

How do I identify my gear ratio before buying a used axle?

Check the gear ratio tag on the differential cover or axle housing, or read the axle code on your door jamb label and cross reference it to a ratio. Confirming this before ordering ensures the replacement matches your front axle on 4X4 applications.

Does the 2017 F450/F550 rear axle have a limited slip differential option?

Yes, the M300 can be configured with a limited slip differential, so it is important to specify whether your truck has limited slip when ordering. Also confirm ABS and disc brake setup, since the M300 mounts its ABS sensors inboard near the differential.

Why choose a remanufactured axle over rebuilding my own?

Rebuilding the M300 requires precise pinion bearing preload and gear mesh, and an off setup will howl and fail again. A remanufactured drop out assembly built to the correct ratio and configuration lets you skip the special tools and the repeat teardown that follows a bad rebuild.

What should I inspect on the axle before installing it?

Look down both tubes for bends and check the housing around welds and spring perches for cracks. Grab the pinion yoke and test for play in every direction, confirm the ratio tag, and verify the cover and pinion seal are dry before installation.