USA Standard Master Overhaul Kit For The Ford 9in Lm501310 Diff

If the 9-inch under your F-100, early Bronco, Mustang, Galaxie or Fairlane has started to howl at 50 mph, rumble louder as speed climbs, or leave a ring of gear oil on the pinion yoke, the bearings in the third member are worn out. The USA Standard Gear ZK F9-B master overhaul kit puts new bearings, races and seals into a Ford 9-inch center section that runs the LM501310 carrier bearing race. USA Standard is the value line from Yukon Gear & Axle, and this version is built with Koyo bearings and races, which makes it the budget-friendly way to freshen a 9-inch for a daily driver, a work truck or a street build.

What a master overhaul kit does in a Ford 9-inch

Nothing on a 9-inch is serviced through a cover. The ring and pinion, the carrier and the pinion support all unbolt from the housing as a single drop-out third member, and every adjustment is made on the bench. The pinion sits in a separate support with two tapered roller bearings, and its nose rides in a small straight roller pilot bearing cast into the case. The carrier spins on two tapered side bearings, and their preload and the gear backlash are set by threaded adjusters on each side. Every one of those bearings controls where the pinion teeth meet the ring gear. Once they wear, the pinion walks under load, the contact pattern moves and the gears start to sing. This kit replaces the whole bearing and seal package in one box so you are not mixing new and tired parts.

Listed contents of the ZK F9-B:

• Carrier bearings and races for the LM501310 race, plus pinion bearings and races
• Pinion pilot bearing and a new pinion seal
• Crush sleeve and pinion nut
• Complete shim kit and ring gear bolts
• Thread locker, gear marking compound with brush, and the third member gasket

Symptoms this kit fixes

• A whine under steady throttle that goes quiet or changes pitch when you lift off
• A low growl that rises with road speed and does not change in turns, typical of carrier bearings
• Driveline clunk when going from gas to coast, from a pinion that has lost preload
• Gear oil seeping past the pinion seal and slinging onto the underside of the truck
• Metallic glitter in the oil or on the magnetic drain plug

How to confirm before ordering

A worn axle shaft bearing can sound exactly like a differential bearing, so check the wheel ends first; if those are the problem, the Yukon 9-inch tapered axle bearing and seal kit is the right part instead. With the rear in the air and the transmission in neutral, grab the yoke and try to move it up, down, in and out. Any play means the pinion bearings are done. Then drop the third member, wipe the ring gear and look for chipped, pitted or blued teeth. Gears in that condition should be replaced along with the bearings; the Yukon 3.50 ring and pinion for the 9-inch is a common choice.

Fitment

This kit is for Ford 9-inch third members that use the LM501310 carrier race with LM501349 carrier bearings. Catalog notes list a 1.625 in. carrier journal and a non-Daytona pinion support. The application list runs from 1957 Ford F-100 and Fairlane through 1986 Bronco and late-1980s F-150 and E-150 vans, along with Mustang, Falcon, Galaxie, Thunderbird, Ranchero, Cougar and Comet. The catch is that Ford built 9-inch carriers with different bearing sizes over those years, and many axles have been swapped since they left the factory, so the vehicle list is a starting point only. Pull the third member and read the number on the carrier race before you order. LM603011 races need the USA Standard ZK F9-C kit, and if you prefer Timken bearings for this same LM501310 setup, the Yukon YK F9-B is the upgrade. Send us your race numbers or your year, model and VIN and we will confirm it. Browse more in our rebuild kits collection.

Install notes

• Before teardown, measure and record the existing backlash and run a pattern with marking compound; it tells you where the old setup was.
• Mark the bearing caps side to side. They are matched to the case.
• USA Standard's setup chart for a 9-inch with OEM gears lists 13 to 15 in-lb of pinion bearing preload with new bearings and 0.010 to 0.016 in. of backlash; aftermarket gear sets call for 0.006 to 0.010 in.
• A crush sleeve collapses at roughly 300 to 400 lb-ft on the pinion nut, so creep up on preload in small steps. If you overshoot, install a new sleeve rather than backing the nut off.
• If the pattern says the pinion depth is off, a 9-inch pinion depth shim set gives you more sizes than the kit supplies.
• Torque ring gear bolts and carrier caps to 60 lb-ft per the same chart, then fill with 75W-90 gear oil, or 85W-140 for heavy towing or high-horsepower use.

How do I tell if my 9-inch uses the LM501310 race?

Remove the third member and read the number stamped on the carrier bearing race, or measure the carrier journal. This kit is for the LM501310 race with LM501349 bearings on a 1.625 in. journal. If the race reads LM603011 or LM102910 you need a different kit.

What is the difference between this kit and the Yukon YK F9-B?

Both cover the same LM501310 9-inch and include the same type of parts. The USA Standard ZK F9-B uses Koyo bearings and races and costs less; the Yukon YK F9-B uses Timken bearings and races.

Will it work with a Daytona pinion support?

No. The catalog notes list this kit for the non-Daytona pinion support. Daytona supports use a larger pinion bearing, so check your support before ordering.

Can I reuse my original ring and pinion?

Yes, if the teeth are not chipped, pitted or heat-blued. Set it up to the used-gear specs and match the old contact pattern. USA Standard's chart lists 6 to 7 in-lb of pinion preload when reusing bearings, but with a new bearing kit you set new-bearing preload of 13 to 15 in-lb.

What gear oil should I use after the rebuild?

75W-90 gear oil is standard for a 9-inch, with 85W-140 common for towing and high-horsepower builds. Add friction modifier only if the carrier is a clutch-type limited slip.

Does the kit include a crush sleeve or a solid spacer?

It includes a crush sleeve and new pinion nut. If you want to eliminate the crush sleeve, the Allstar ring and pinion installation kit uses a solid spacer instead.