King Pin Replacement
By Stephen Kassis
King pins on Chevrolet cars and trucks are a vital part of good steering and vehicle control. There are two different designs. The early design requires pressing bushings into the spindle and using a reamer to fit the pin to the bushings. The later design is called a floating bushing type. In this design, the bushings do not require pressing for installation and they do not require reaming for fit. The bushing is precision fit for the pin at the factory and the bushings should just push into place in the spindle. Installation of the two different types is similar but the free floating type is much quicker and easier to install. For purposes of this article, the focus will be on the press fit & ream type bushings as the rest of the installation will be the same on both types. Consult the shop manual for your car or truck to determine the type of bushings in your vehicle.
One tip for the floating bushing king pins, before starting on the press fit style: Sometimes the floating bushings will fall through the opening in the spindle when inserted for installation. A simple fix is to use bearing grease on the outer surface of the bushing and inner surface of the spindle holes. This will hold the bushings in place long enough to install the pin.
It is recommended that photos be taken during this process to assist in re-assembly. Jack up the front of the vehicle and place it on good quality, four point jack stands. Remove hubcaps, wheels and tires. Remove the hub dust cover, cotter pin and spindle nut. Pull the hub & brake drum off while keeping the outer bearing from falling out of the hub. This is a good time to inspect the condition of the wheel bearings and repack them with fresh grease. Keep bearings protected to prevent contamination.
Inspection of the brake drums and brake shoes is quick and easy at this stage, so take advantage of the opportunity. Address any issues with these as a separate project.
With the hub removed, slide the inner bearing dust shield and inner race off of the spindle. This will expose the brake backing plate. This plate must be removed but anything connecting the backing plate to the chassis must be removed first. This would include brake housings and cables on mechanical brake systems or brake hoses on hydraulic systems. When removing hydraulic brake hoses press a rubber plug into the opening on the wheel cylinder. Also cover the end of the brake hose with a plastic bag and seal with a rubber band. These steps will prevent contamination. Note: On some hydraulic systems, the backing plate can be removed with the brake hoses in place. This will save time having to bleed the system afterward.
There will be four main mounting bolts that hold the backing plate to the spindle. Remove these, taking note that some applications will have two different size and/or different length bolts. Also, some bolts will have cotter pins and some just lock washers holding things together. Make sure you note the differences and positions before disassembly to reinstall exactly as removed.
With the bolts removed, the backing plate will slide off of the axle, exposing the spindle, axle and king pin. Check the brake shoes for wear and wheel cylinders for leakage. Replace or repair if necessary. Clean the backing plate and set aside for installation later.
Remove the dust cap (soft plug) on top of the spindle by striking it with a chisel on the edge. Once the dust cap is removed, unbolt and remove the tapered lock pin that is mounted horizontally into the axle housing. With this pin removed, drive the king pin down and out of the axle and spindle. The spindle is now free of the axle. Remove and discard the bearing but retain any undamaged shims for possible use later. Note the location of the bearings and shims as they are disassembled. Clean the axle and spindle of dirt and grease.
With the spindle cleaned, inspect the bearing surfaces for signs of damage. The damage will be on the bottom edge of the spindle surface which is holding the weight of the vehicle. If a bearing race has spun, it can damage the spindle causing loose bearing fit and also causing misalignment. This in turn can cause irregular wear on tires or steering to “wander”. If your spindles have this kind of damage, you can try to find suitable replacements. Check by sliding a thumbnail over the irregular surface. If the nail catches, it is more than .010″ worn and needs to be addressed. Another option would be to have the spindle industrial chromed and turned back to standard. Industrial chroming is a very hard surface that can be used to save an otherwise difficult to find part.
Open the new king pin set and check the components. There should be two king pins, four bushings, two bearings, shim packet, two lock pins with lock washers and nuts. Some installations require other special parts, but this list should be the minimum in the kit. If you buy a kit at a swap meet or on line, be sure that you are getting a complete kit.
Early Axles with Press Fit Bushings
The bushings must be removed by driving them out of the spindle. This is best done in a vise with a bushing driver. Drive out the old bushings and drive in the new. CAUTION: When driving in the new bushings, pay special attention to see if there is a grease hole in the bushings. If so, this hole must line up with the grease fittings in the spindle to allow proper grease flow to the bushings. With the new bushings in place, they must now be reamed. The proper reamer must be used to keep the alignment straight and get the proper fit of the spindle to the pin. If a proper reamer cannot be obtained, it is suggested that the spindles be taken to a machinist for proper fitting. Proper bushing alignment is vital and misalignment will damage the bushings beyond being useful.
Once the pin fit has been checked, clean any foreign material from the bushings and lubricate the bushings with wheel bearing grease. Pack grease into the new bearings provided in the king pin kit. Check the fit of the new king pin in the axle. The new king pin should fit snugly in the end of the axle. If there is too much play in the end of the axle, it would be best to find another axle. Though oversize king pin sets were available years ago, these are somewhat hard to find. Even if found, the boring of the old axle must be made at precisely the correct angle and bore size. This process would have to be done at a qualified machine shop. Replacing a worn out axle will probably be easier and cheaper.
Install the spindle with the bearing at the bottom. Use new shims in the king pin set to take up any slack between the bearing, axle and the spindle. If there are not enough shims provided, clean and use some of the original shims that were saved on disassembly. There should be no looseness between the bearing, axle and spindle but the spindle should turn freely on the end of the axle.
Slide the new king pin into the top of the spindle bore, taking note of the flat spot on the side. The flat area on the king pin must align with the hole for the horizontally installed tapered locking pin. Push the king pin down until the hole for the locking pin is open. Install the tapered locking pin into the horizontal hole. Install lock washer and nut and tighten down until the pin is seated securely in the axle. On many models, there is also a wheel stop that is held in place by this pin. Be sure to install the stops when installing the lock pins.
Install the dust caps (soft plugs) in the top and bottom of each king pin. Hit the convex rounded surface with a couple of good blows to expand the plug in place. Pump a little grease into the fittings to insure good lubrication of the bushings and pins.
Check for free spindle operation from front to back. If everything is installed properly, there should be no up and down movement in the spindle and the forward to back movement should be smooth. If your installation passes these checks, continue to install the backing plates, dust seals, hubs & drums, wheels & tires in reverse order explained above.
