Modifying your RV or SUV according to a fifth wheel means more than simply purchasing several devices. In fact, this process requires choosing the best quality models, equipment, tools, and knowing about the details. If you are willing to be involved in every stage, from 5th wheel installation to getting specialized in maintenance and repair, you should be familiar with the units of a fifth wheel. So, let’s first enumerate the basic parts you will commonly encounter: fifth wheel hitch, fifth wheel plate, the trailer hitch, and the kingpin.
This last piece may seem the smallest, yet its function and significance are crucial during operations. This is because the main purpose of the 5th wheel is to tow heavy duties, which a standard vehicle in urban use cannot. And therefore, much is about the stability, strength, and integrity of the connection point. Here comes the importance of the kingpin, namely the device that serves this essential purpose. Before learning the installation basics of the kingpin, let us get more information about the features and function of this device.
Get to Know about your Kingpin
Actually, the name of the kingpin itself initially announces it’s importance for the fifth wheel. Being the primary pivot in the steering system of an automobile or other vehicle, the kingpin allows the steering wheel to rotate. Additionally, it refers to a component of the coupling apparatus for a fifth wheel used by a semi-truck to attach to a trailer or another load.
The kingpin establishes the link between the tractor and the semitrailer. In this sense, it is a crucial component of the fifth wheel connection. The kingpin setting refers to the distance that exists between the center of the fifth wheel connection and the center of the rear axle group. This distance plays a role in determining the turning radius of the vehicle.
This measurement increases proportionally with the length of the kingpin setting. Therefore, the kingpin setting and the sturdiness of the device determine your duty performance and set the limit you can tow with your vehicle.
The kingpin installation seems like a really simple process but note that there is a lot to it. A lot of you may run into several problems when you buy an old axle and just try as you might but cannot get the kingpins out. So firstly, fast axles, tow axles, and trailer axles all have one single set screw holding the kingpin in the middle. When you drop your kingpin, it hits right that point in the middle. The two set screws on the axle provide the kingpin with more stability inside the boss.
The kingpins may easily get rusty. So before installation, be sure that they are smooth enough. Besides, the kingpin should have a recessed area so that when you push the set screw into the kingpin, any mushrooming that creates instability when you tighten the kingpin right down will not expand beyond the diameter of the device. Once you have accommodated your kingpin suitable for installation, there are several steps to follow.
Following the 10 Steps
- To check horizontal movement, attach a dial indicator with a magnet to the top of the axle. The dial indicator should rest on the spindle eye. Keeping the wheel end and tire together, put a pry bar under the tire and move it up and down while measuring how much the dial indicator's needle moves. If the kingpin moves more than 0.010", it needs to be changed.
- Take the wheel off along with the brake assemble, the plate on the back the steering arms, and the crossbar, respectively. Then, take off the top and bottom plates of the kingpin. Remove the locks and the kingpin. (Don't use heat; use a hardened punch instead) Use a bottle jack or a hydraulic press without heating it. Save the shims for later use. Take off the spindle and do the same thing on the other side of the truck. Clean the axle eyes and spindles so that they can be checked.
- With a brass hammer or a dead blow hammer and a "ST" Series STEMCO Kaiser bushing driver, pound the bushings out of the spindle eyes. When it comes to a seal, the bushing will push it out. Do not use a punch or chisel, as this could damage the spindle eyes so much that they can't be fixed.
- Check to see if the axle eye is out of round, and then check to see if the spindle eyes are out of round. Use a micrometer and a T-gauge to see if they are up to snuff. Use a hand drill with a brake hone to lightly smooth out the axle eye until it is smooth. Don't hone too much; just clean this surface.
- Put the seal on the end of the driver with the beveled edge facing out. Use a brass hammer or a dead blow hammer to pound the seal into the spindle eye until the driver is flush with the bottom of the spindle eye. Lasty, take out the driver.
- Hold the spiral steel bushing in your hand at an angle and twist it into the spindle eye by turning it clockwise. Install it by hand as far as you can, then use a tool with a T-handle to twist it in. Using a brass hammer, tap the rest of the bushing into the spindle until it is flush.
- Try fitting the kingpin into the top bore. Repeat the steps for the bottom bore. To check if the spindle is aligned, slide a pin through both holes. If the kingpin won't fit into the opposite spindle eye spindle, the eye spindle should be changed. Count how many shims you took off the old kingpins. These will help you figure out how many to put back in. Find out how thick the previous stack of shims was and start by adding back 0.005" of what you took out. Before putting in, grease the bearings.
With the word "TOP" on the top of the kingpin facing the end of the spindle, put the kingpin into the top spindle eye and slide it through until 12 inch of the pin comes out the bottom. Make a crease in the last shim on the pack and put shims on the kingpin to make installation easier and protect your fingers. Lift the spindle and put it on the axle. Then, put the kingpin into the hole and let it fall. Push the kingpin down until the bottom of it is even with the bottom of the axle. Put the open side of the bearing down using the palm of your hand. If you can't install the bearing with the palm of your hand, take the assembly apart and remove 0.005" from the shims. If you can put it in with your fingers, take the assembly apart and add another 0.005" shim to the stack. Install lock(s). Use TULGA Adapter Heavy Duty Semi Turck Trailer Kingpin Converter for Fifth Wheel Plates. Made from strengthened steel material, this device ensures an additional stability. Make sure the lock pin's flat side is facing the kingpin. Install the nuts, and washers, and tighten them to the torque spec, which is usually 30-45 ft.lb. Put the top and bottom plates in place and tighten them.
- Put the grease gun on top of the zerk fitting. Move the spindle from side to side while pumping grease into the fitting until grease comes out between the spindle and axle. If the spindle doesn't move smoothly, either there are too many shims or the bearing is broken. Attach the grease gun to the bottom zerk fitting. Move the spindle from side to side as you pump grease into the fitting until grease comes out of the top of the bearing.
- Put the steering arms and crossbar back in place. Then do the same for the wheel, the brake assembly, and the backing plate. Attach a dial indicator with a magnet to the top of the axle so that the dial indicator rests on the eye of the spindle. Keeping the wheel end and tire together, put a pry bar under the tire and move it up and down while measuring how much the dial indicator's needle moves. (There shouldn't be much movement.)
Choosing the High Quality
Given the significance of the kingpin for the fifth wheel, you shall expect it to be of the highest quality. The most important feature is sturdiness. TULGA offers you TKKP 2’’ Heavy Duty Semi Trailer Kingpin for the harshest duties, with a lifetime warranty. This product is suitable for almost all trucks in the world, making it popular among truckers and RV drivres. Another commonly preferred product is Fifth Wheel Kingpin TFKP 2’’ & 3.5’’ Heavy Duty Trailer Kingpin, which provides you with the most stable and enduring attachment.
If you want to know more about TULGA products and the fifth wheel installation, our blog is the next step in your adventure! Always at the service of safety and the best quality.