by Steve Turchet
Back in the 1970s, I worked for a scrap metal company in Arizona, dismantling old mining sites in the desert. At the time, my truck was a 1966 M37. It carried my tools when I went out to repair and maintain the company’s equipment. I put a lot of miles on that truck, and I thought I was keeping it in top condition. I did frequent lube jobs and oil changes, as well as checked it over at regular intervals so I could fix things before they broke.
While out on a job one afternoon, however, I noticed that one of my truck’s front wheels didn’t look right. It seemed to be leaning inward at the top. I went over and shook the wheel but couldn’t find any apparent looseness in the wheel bearings or steering knuckle. But, when I jacked the truck’s front end off the ground, I discovered the steering knuckle was dangerously loose. After pulling the knuckle apart, I found the upper pivot bearing had disintegrated! I wondered how this could have happened since I always kept the truck well-lubed.
This is a good example of why you should perform regular inspections of your vehicle’s steering knuckles. Just doing lube jobs is not enough. These inspections are twice as important if you own a vintage historic military vehicle (HMV) with ball-knuckle steering joints and is fitted with locking hubs – as was my M37.
LOCKING HUBS? BEWARE!
On many ball-knuckle vehicles, the steering pivot bearings (the upper bearings in particular) were meant to be lubricated by the splash of oil from the rotating universal joint. If the vehicle has locking hubs and is used mostly with the hubs disengaged, the upper bearing doesn’t get oiled. Therefore, it will eventually wear out. If your HMV has locking hubs, you should lock them and drive a few miles every week so the steering knuckle U-joints rotate and splash the oil around. This advisory used to be included with many brands of locking hubs.
INSPECTION IS THE BEST PREVENTION
While looseness or wear in a vehicle’s steering knuckle may often be discovered while performing a lube job – assuming you’re paying attention – a more thorough inspection can be performed by jacking your vehicle’s front end off the ground by its bumper or frame so the axle and wheels hang from their springs. (Note: This, by the way, is also the best method of lubing the spring shackle bushings. Why? If you lube them with the vehicle on the ground, the grease can’t get into the upper part of the bushings because the vehicle’s weight is on them.)
Take proper safety precautions when jacking a vehicle’s front end, such as blocking the rear wheels and using adequate jacks and supports. Be careful when jacking up HMVs with sprag-type transfer cases, such as early model M35s, because a front wheel may spin when leaving the ground.
We don’t have the space to show the steering knuckle components of every common hobbyist HMV, but the illustrations in this article of a CCKW assembly should give you a good idea of what most ball-knuckle steering joints are all about. Except for size, most ball knuckle front axles are basically the same in the arrangement of their parts. Specifics are covered in manuals, and if you don’t already have a manual for your vehicle, it would be smart to get one.
Once the front tires are clear of the ground, point them straight ahead, then grab a wheel by the top of the tire and try to wobble it back and forth. If the wheel bearings are loose, the wheel will wobble on its spindle. However, if the steering knuckle bearings are loose, BOTH the wheel assembly and the outboard portion of the knuckle will wobble.
On many jeeps the pivot bearings are bronze bushings, while larger HMVs usually have tapered roller bearings. Many HMVs have shims to adjust the tightness of these bearings – and here is where having a manual is important.
There should be no looseness in the ball-knuckle bearings – none at all. Even if they seemed tight in the wobble test, get a helper to turn the steering wheel. Watch each knuckle while the steering is run through a full cycle from one side to other and brought firmly against the stops, both ways.
Watch what happens when the knuckles reach the end of their travel. The outboard portion of the knuckle should NOT appear to rise or lift – even slightly – when it bottoms out against its stop. Sometimes, even if the bearings seemed tight in the wheel wobble test, you may still find looseness in this second test. If there is looseness, the ball-knuckle should be disassembled to find the cause.
While many larger HMVs have lube fittings top and bottom on their steering-knuckles, many smaller vehicles don’t. Most HMV owners know that ball-knuckle joints usually leak oil. However, instead of fixing them with new seals, some folks shoot the balls full of grease. Bad idea! Grease doesn’t splash around, so it can’t lubricate the upper bearing, nor will it run down into the lower bearing. Ball-knuckle steering joints designed to use oil are no different from transmissions, transfer cases, axle differentials, or winch gear boxes. The manufacturers knew they would leak a little around the seals. That’s why they provided plugs to check the oil level and top it off.
Just like the other above-mentioned components, the oil in ball-knuckles should be changed when it looks dirty, becomes contaminated with water or metal particles, or simply breaks down from age. Even if you don’t drive your vehicle a lot, all its gear oil should be changed about every five years.
Most ball-knuckle joints use the same 90 weight gear oil as the vehicle’s transmission, transfer case and differentials. Just like those other components, they will benefit greatly from top quality oil.
If a ball-knuckle is leaking excessively, replace the seals. That’s the only real fix.
Keep the balls clean on the outside. If they’re rough or rusty, use fine sandpaper or crocus cloth to polish them, and then wipe them occasionally with an oily rag. They should always be shiny.
Clean off dirt or mud if you take your vehicle off-road. If you’ve driven through deep water, check the oil for contamination and replace it if necessary. Of course, if your vehicle’s ball-knuckles are provided with lube fittings, you should lube them at frequent intervals. Doing these simple things will greatly prolong the life of the seals as well as the life of the steering pivot bearings.
If you have to replace the pivot bearings, replace their races as well. Generally, it’s the upper bearing that gets the most wear, but you should always replace both upper and lower bearings at the same time, and on both ends of the axle. You may find that on some smaller HMVs that use bronze bushings, you can get roller bearings and races instead of bushings. Pack the bearings with wheel bearing grease before installing.
To begin disassembly, remove the wheel and hub from the axle spindle. This will be easier if you first remove the tire and road wheel. Some large HMVs have drain plugs on the bottom of the knuckle assembly, but most vehicles most don’t so have a pan to catch the oil when the knuckle comes apart.
Remove the drive-flange nuts or bolts. You may need to use the flange’s puller screws to take the flange off. It’s a good idea to line up all the parts as you remove them in a row on your workbench or floor in the order they came off and in the direction they were facing, and to keep them in that order as you wash or clean them. This makes reassembly easier.
Some vehicles have an oil seal behind the drive flange, but usually there’s only a paper gasket, which will probably be destroyed on disassembly. You can make a new one from gasket paper.
Removing the drive flange should reveal the axle spindle and wheel bearing lock nuts. Usually there are two nuts with a retainer that hold the wheel hub on the spindle. On most vehicles these nuts look like nuts, having six sides, though some GM vehicles have threaded rings instead of nuts.
Generally, there is a tab-type retainer with one tab bent over the inner (adjusting) nut and another tab bent over the outer (locking) nut. Sometimes this retainer is a simple metal disk with an edge bent over the outer nut, while on other vehicles it may be a spidery-looking thing. Use a small chisel or a screwdriver to straighten the tabs on the disk so you can remove the outer nut. Be gentle with the retainer, because on older vehicles, it has usually been bent, straightened, and bent again many times. It is probably fatigued.
Removal of the spindle nuts is best accomplished with the proper spindle nut wrench, especially if the nut is not a conventional type. However, you probably don’t have such a wrench, and it’s likely that whoever was in there before you didn’t have one either and used a hammer and chisel. If this is the case, be sure your chisel is sharp, your hammer is small, and try to do as little damage as possible to the nuts.
Usually it will only take a few taps with the hammer to get the nut loose, after which you can unscrew it with your fingers. Beware of sharp edges left by a chisel.
When the outer nut is off, remove the retainer. Sometimes you will need to walk it off using two small screwdrivers as levers. Then remove the inner nut. Some of these nuts have a raised shoulder or boss on the inner side which fits against the outer wheel bearing, and/or a dowel on their outer side which engages a hole on a ring-type retainer. Keep these details in mind for correct reassembly.
Sometimes there’s a spacer between the inner nut and the outer wheel bearing. Remove this, if present, and note how it was installed.
Now, by gently rocking and pulling on the hub, the outer wheel bearing should come loose and can be pulled off the spindle. Sometimes the bearing will pop off by itself and land in the dirt, but no matter, you will be cleaning it anyhow – though having it bounce off a concrete floor is not a good thing!
With some additional rocking and pulling, remove the hub from the spindle, being careful not to drag the inner wheel bearing and oil seal over the spindle threads, possibly messing up the threads or cutting the oil seal.
Now you should be ready to disassemble the steering knuckle according to the illustrations here – or preferably in your manual – and the procedure is basically the same whether you’re working on a jeep or a G-792.
Reassembly is merely the reverse of disassembly. Once the knuckle is back together, check that it pivots smoothly all the way, both left and right, and there is no looseness in the bearings.
If you were up to this job of replacing your ball-knuckle bearings, you will also know how to clean and repack your wheel bearings. Here is the procedure for reinstalling the wheel hub:
Slip the hub back on the spindle and seat it over the brake shoes, then install the outer wheel bearing and inner retaining nut. Don’t forget the spacer if there was one.
Make sure the brake shoes aren’t dragging on the drum… if so, back them off a bit. As the nut is tightened, you will notice an increase in turning resistance when rotating the hub as the bearings are seated in their races.
When the bearings are properly seated, the hub should rotate smoothly and freely with no wobble on the spindle up to the point where further tightening causes the hub to slow down and noticeably increases the turning resistance.
Recap: The hub should rotate freely but not wobble on the spindle. (New or freshly repacked wheel bearings will sometimes loosen slightly after a few miles of driving and may need to be adjusted again.)
Slip the retainer into place, followed by the locking nut, and draw the nut up tight. Bend one of retainer’s tabs across a flat of the inner nut and another over the outer nut.
If your vehicle has locking hubs instead of a drive flange, follow the directions for installing them – we’ll assume you cleaned and serviced them, too. On early jeeps, install the axle nut, cotter pin (if used), and the dust cap.
You have just completed a vital bit of repair on your HMV! By performing regular lube jobs, as well as inspections, you may not have to do it again for a long time.