Backhoe Loader (JCB) and Grader King Pin Kit: Parts, Wear Signs and Fitment

A backhoe loader whose front wheels clunk when you turn the steering on the spot, wander on the road and wear one edge of the tyre faster than the other usually has worn king pins. A JCB king pin kit is the set of parts that renews that joint at one front wheel: an upper and a lower king pin, the bushes or bearings they turn in, seals, shims, grease nipples and the bolts that hold it all together.

Most people in India say “JCB” when they mean any backhoe loader, and this guide uses the word the same way. It covers what a king pin does, which machines have one, what comes in a kit, how to spot wear and how to order the right kit. It gives no prices, because a king pin kit changes with the axle maker, the axle serial number and the seller, and a printed figure would be wrong for most readers.

What is a king pin on a JCB?

It is the pivot that a steered wheel turns on. Each front wheel of a backhoe loader is carried by a swivel housing (also called the steering knuckle or hub carrier), and that housing is joined to the end of the axle by two short, hardened pins, one above the wheel centre and one below. When the steering cylinder pushes the housing, the wheel swings left or right around the line joining those two pins.

The pins carry more than steering. The weight on that corner of the machine, and every shock from a stone or a pothole, passes through them, which is why they are thick, turn in bushes or bearings, and need grease.

The Wikipedia entry on the kingpin describes it as the main pivot in a vehicle’s steering, a name dating from horse-drawn wagons. Cars replaced the separate pin with ball joints long ago, but it is still used on heavy steer axles such as those on trucks.

Do not confuse the king pin with the king post. The king post is the big swing joint at the back of a backhoe loader that the digging boom hangs from. It is explained in the backhoe loader parts guide. The two parts have nothing in common except the name.

Which machines have king pins?

Any machine that steers by turning its wheels on a solid axle has them. Machines that steer by bending in the middle, or by slowing one side, do not. The specification sheets of the machines listed on DesiMachines show the split clearly.

Two points come out of that table. First, a grader leans as well as steers. Its front wheels tilt sideways under hydraulic control to stop the angled blade pushing the machine off line, and a grader axle patent filed by Deere (US 8,412,420) describes the usual layout: a yoke at each end of the front axle, joined to the wheel spindle by an upper and a lower king pin. The motor grader parts guide covers the lean links and tie rods that work with them. BEML lists reverse-Elliot front axles on the BG825, BG605I and BG405A and an Elliot-type axle on the BG605A, and the Komatsu GD825A-2 lists the reverse-Elliot type too. Those names describe how the pin meets the axle, explained in the next section.

Second, on a Hydra the word “king pin” usually means the pins in the articulation joint, not a steering knuckle. The Hydra crane parts guide lists the king pin and articulation bearings among the parts that wear first on a Hydra such as the Escorts Hydra 14. When you ask a seller for “king pins” for a Hydra or a wheel loader, say which joint you mean.

How is a king pin fitted to the axle?

There are two common shapes. In an Elliot axle, the end of the axle beam is forked, and the steering knuckle sits inside the fork. In a reverse-Elliot axle, the end of the beam is a solid eye and the knuckle forks around it. The 1942 to 1947 Chevrolet truck shop manual describes the reverse-Elliot pin plainly: it sits in a hole bored through each end of the I-beam, is locked in place by a tapered pin and nut, and is bored at a slight angle so that it leans inward at the top. That inward lean is called kingpin inclination, and it is what makes the steering want to return to straight ahead.

On a backhoe loader the joint is built around the swivel housing. Parts lists for the Carraro steer axles fitted to Case and Cat backhoes show a separate upper king pin and lower king pin on each side, passing through the housing into the axle arm, with the lower pin held by three bolts on some versions. Other axle makers arrange the same parts in their own way.

The parts of one king pin joint, top to bottom

What is in a JCB king pin kit?

A kit covers one joint or one side, and the contents follow the axle design. A full kit for a backhoe loader steer axle usually holds:

• the upper and lower king pins
• the bushes, or the taper roller bearings on axles built with bearings
• thrust washers or a thrust bearing, which carry the up-and-down load
• seals and dust covers that keep grease in and mud out
• shims in more than one thickness
• grease nipples, bolts, and on some axles a spring (Belleville) washer under the lower pin

The shims matter more than they look. They set the preload, which is how tightly the pins are clamped so the housing turns freely with no play. The Broken Tractor parts list for the Carraro four-wheel-drive axle on Case 580-series backhoes offers king pin shims in 0.10 mm, 0.19 mm and 0.35 mm, and warns that some pins and washers changed at a particular axle serial number. That is the general lesson: the axle serial, not just the machine model, decides which kit fits.

Some sellers offer a smaller set with only the pins and bushes. On a joint that has run dry long enough to wear the pin, the seals have usually failed too, so the full kit is the safer buy. The bucket and boom pins on the same machine are a different job and a different kit, covered in the pin bush kit guide.

If you are about to put money into an old machine’s front end, compare that bill with what a newer machine costs to run. Browse current backhoe loaders, such as the JCB 3DX, Mahindra Earthmaster SX and CASE 770 NX, and talk to a dealer.

How do you know the king pins are worn?

The joint gets loose, and the looseness shows up in the steering and the tyres before you can see anything. Look for these, roughly in the order they appear:

• a clunk or knock from the front corner when you turn the steering with the machine standing still
• steering that feels vague, or a machine that wanders and needs constant correction on the road
• a front tyre wearing faster on its inside or outside edge
• shaking felt through the steering wheel at travel speed
• on a grader, a finished surface with a slight wave in it, because the front end will not hold its line

To check, park on firm level ground, raise the front wheels clear with the loader arms, and put stands under the axle before anyone goes near the wheel. Never rely on the hydraulics alone to hold the machine up. Then grip the tyre at the top and bottom and rock it. Have a second person watch the joint. If the swivel housing moves against the axle arm, the king pins or their bushes are worn. If the hub moves on the housing instead, the wheel bearing is the likely problem, which is a different part.

Also look at the seals around the pins. A seal that is torn or pushed out, or a joint that takes no grease when you pump the nipple, means dirt is already inside.

The steering system as a whole, including the steering type and pressure each backhoe loader publishes and the oscillating front axle, is covered in the backhoe loader steering and front axle guide. The front tyre sizes by model are worth checking at the same time, since a worn joint ruins tyres.

Why do king pins wear out?

Mostly through missed grease. Every king pin joint has a grease nipple, and on a backhoe loader those nipples sit low at the front wheels, in the mud and water. When greasing is skipped, the old grease dries or washes out, dirt gets in, and the pin and bush grind each other down. The greasing guide lists the points on each machine and how to grease them, and the operator’s manual gives the interval for your model.

Load makes it worse. On a backhoe loader the front shovel’s load sits ahead of the front axle, so the front king pins work hardest when the machine is loading a tipper. Turning the steering while standing still on hard ground, with a full shovel, twists the tyre against the ground and pushes the full load through the pins. Once is harmless; all day, every day, wears a front end out early.

A worn pin also wears unevenly. A technical note from STEMCO, which makes king pin kits for trucks, warns that worn pins often grow a raised lip at each end where they ran in the bush, and that this lip has to be removed before new bushes are sized. It also says the new bushes are fitted into the housing bores and then reamed to size. In plain terms, changing king pins is a workshop job with a press and a reamer, not a roadside one.

Do graders and telehandlers use the same kind of kit?

The idea is the same and the parts are not. A grader’s front king pins sit between the axle yoke and the wheel spindle, and the lean mechanism moves the yoke, so the kit is specific to that axle and the wear pattern often shows up as a grader that will not hold a straight line. Graders such as the Mahindra Roadmaster G100 publish their steering angle but not the axle maker, so take the serial number to the dealer.

A telehandler that steers both axles, like the Manitou MXT 840 K, has king pins at all four wheels, which doubles the greasing and the parts. One that steers only the rear, like the JCB 530-70, has them on the rear axle. The telehandler parts guide covers the rest of the steering on those machines.

A transit mixer truck uses an ordinary truck front axle, so its king pin kit comes from the truck maker’s parts range, for example for the Tata LPK 2821.K RMC, which lists a reverse-Elliot front axle.

How do you order the right king pin kit?

Take these to the dealer or parts seller:

• the machine model and its serial number
• whether it is two-wheel drive or four-wheel drive, because the front axles are different
• the axle’s own plate, if you can find it: the maker and the axle serial number
• a photo of the old pins and the housing, once they are out

Ask whether the kit covers one side or both, and whether bushes, seals and shims are included. Buy new seals and grease nipples even if they were not in the quote. After fitting, grease the joint until clean grease comes out, then check it again after the first few days of work.

This is a general guide based on machine type. Always confirm the fit with your machine’s operator manual or the manufacturer before buying or fitting.

When the repair list on an older machine keeps growing, compare the cost with a newer one. Browse the backhoe loaders, motor graders and telehandlers listed in India and speak to a dealer. The other wearing parts on these machines are in the parts and running costs guides.

Where the figures in this guide come from

The machine counts and steering descriptions come from the specification sheets of the backhoe loaders, motor graders, telehandlers, wheel loaders, transit mixers and pick and carry cranes listed on DesiMachines, read in October 2026. One motor grader lists a 20° steering angle, far below the 40° to 50° the rest publish, so it is left out of the range until the figure is checked. The axle descriptions are taken from the reverse-Elliot passage of the 1942 to 1947 Chevrolet truck shop manual, the grader axle layout from US patent 8,412,420, the king pin kit contents and shim sizes from Broken Tractor’s parts lists for the Carraro axles on Case and Cat backhoes, and the bush advice from STEMCO Tech Tip 101.

This guide gives no part prices, because king pin kits vary too much by axle, serial number and seller for a printed figure to stay true. A dealer quote against your machine and axle serial number is the only reliable price.

Prices, specifications and features are indicative, vary by variant, location and date, and should always be confirmed with the official OEM or authorised dealer before any purchase decision. DesiMachines is not liable for decisions taken on the basis of information that may have changed after publication.