Ford 8.8 Ring and Pinion Installation Kit, Ford Racing M4210A

Swapping gears in a Ford 8.8 with good bearings still in it? The Ford Racing M-4210-A is the setup hardware that has to be new every time the ring and pinion change: shims, a crush sleeve, pinion nut, pinion seal and ring gear bolts. Ford Performance lists it for every 8.8 inch axle from 1986 through 2014, solid axle and independent rear alike, which takes in the Mustang, F-150, Explorer, Ranger, Expedition and Crown Victoria owners searching for 3.55, 3.73 or 4.10 swaps. It is small, inexpensive and the reason a regear does not stall on a Saturday afternoon.

What the setup kit does in a Ford 8.8

The 8.8 is a Salisbury-style integral axle. The pinion runs on two tapered bearings in the housing nose, with its depth set by a shim under the inner pinion bearing cone and its preload set by crushing a collapsible sleeve between the bearings as the nut is torqued. The carrier sits on two side bearings, and shims between those bearings and the case locate the ring gear for backlash and load the bearings. A new gear set almost never wants the same pinion shim as the old one, a used sleeve cannot be crushed a second time, and ring gear bolts stretch on their first torque. Ford Performance lists the contents as pinion and carrier shims, crush sleeve, pinion nut, pinion seal and ring gear bolts. There are no bearings in the box; Ford describes it as the kit for new gear installs when new bearings are not required.

When this kit is the right buy

• A ratio change on an axle with healthy, quiet bearings that have never run low on oil
• A gear set that came with its own new bearings, so only the shims and hardware are missing
• Replacing chipped or pitted gears after a hard launch when the bearings check smooth

It is the wrong buy if the axle growls with road speed, the pinion has play, or the oil was found low. Those are bearing symptoms, and they call for a full bearing kit such as the USA Standard Ford 8.8 master bearing and seal kit.

How to confirm before ordering

Spin each old bearing by hand once it is clean. Any roughness, flat spots or pitting on the rollers or races means they go in the scrap bin and this kit is not enough on its own. Our carrier bearing noise guide explains how bearing noise differs from gear whine, and the Ford 8.8 rear axle problems guide covers the usual failures, from pinion bearings to Traction-Lok chatter. If you are not sure how a crush sleeve sets preload, read crush sleeve versus solid spacer first.

Fitment

Ford lists M-4210-A for all 8.8 inch axles from 1986 to 2014, including IRS. The 2015-and-later Super 8.8 IRS is a different design, and Ford sells a separate installation kit for it (M-4210-B3), so a 2015-up Mustang or later F-150 is not covered by this part. If your axle is a front 8.8 in an independent front suspension 4x4, or you are unsure which rear you have, read the axle tag and send us the year and VIN before ordering. The rest of our 8.8 parts are in the rebuild kits category.

Install notes

• Remove the cover, the pinion shaft bolt and shaft, push the axles in to free the C-clips, and pull the shafts before removing the carrier.
• Press the inner pinion bearing off the old pinion to recover the shim, measure it, and adjust for the new gear set. Revolution Gear and Axle lists a 0.026 in starting shim for the 8.8.
• Fit the new crush sleeve and tighten the new nut a little at a time. Revolution's chart gives 14-19 in-lb of rotating torque with new bearings; reused bearings are normally set lighter, so follow your manual.
• Set backlash in the .006-.010 in range with the carrier shims, then check the contact pattern before final torque. The chart lists 60 ft-lb for ring gear bolts and 60 ft-lb for caps.

Refill with the gear oil grade on your axle tag or owner's manual; many 8.8s call for 75W-140 synthetic, some later axles 75W-85. A Traction-Lok needs friction modifier unless the oil already has it, and if it still chatters the Traction-Lok clutch rebuild kit is the next step. Gear sets to pair with this kit include the Motive 8.8 3.73 set and the Revolution 8.8 3.55 set. Break new gears in gently and change the oil early, as laid out in our break-in procedure.

Does M-4210-A come with bearings?

No. It includes pinion and carrier shims, crush sleeve, pinion nut, pinion seal and ring gear bolts only. If your bearings are worn, buy a master bearing kit instead.

Will it fit a 2015-and-later Mustang or F-150?

Not the 2015-up Super 8.8 IRS. Ford lists M-4210-A for 1986-2014 8.8 axles and sells a separate kit, M-4210-B3, for the 2015-2023 Super 8.8 IRS.

Does it fit the Mustang and Explorer IRS from before 2015?

Ford's listing says it fits all 8.8 axles from 1986 to 2014 including IRS. Read your axle tag and send us the VIN if you want us to check your exact axle.

Can I reuse my old bearings with new gears?

Only if they are smooth, unpitted and never ran low on oil. The pinion bearing has to be pressed off to move the depth shim, so inspect it closely then.

What gear oil should go back in?

Use the grade on the axle tag or in the owner's manual, often 75W-140 synthetic on 8.8s. Add friction modifier for a Traction-Lok unless the oil already contains it.

What is the shipping weight?

Ford lists the package at about 2 lb, so it ships quickly and cheaply alongside a gear set.