2 Big Broncos Rocky Mountain Site
4340 Chrome Moly Axles and CTM U-joints
(The CTM's aren't in yet, but I have them! More pics when the work is done!)
There is no doubt in my mind any more that these axles are everything the ads say they are. Everything about them is bigger and tougher than the stock axles. The first thing you notice is that there are no reduced sections. The entire shaft is the same diameter as the splines or bigger. When you hit the stock shafts with a hammer, they thud. These things ring like a bell, a rather unscientific measure of hardness.
I don't know exactly who made these axles since they came with the axle assembly I bought. I know the previous owner bought them from Off Road Design, so I think they were probably made by Superior Axle.
The first order of business for these axles was to clean them up and get new u-joints installed. The joints that were in the axles were some used ones the previous owner had laying around. He strongly recommended I replace them, sounded like a BIG hint to me. I don't know if it's due to the 4340 steel or not, but getting the old joints out was a BITCH! It took forever and a lot of coaxing to get the joint caps to start moving. Once everything broke free, the job was like any other u-joint. Another twist on these joints is that they were retained by snap rings instead of circlips. It took a while to find the right combination of tools to get the snap rings off, but after that they were as easy to deal with as any other snap ring. I have a spare set of stock axles that have also been modified for snap rings. When I replace the joints in them I'll have a chance to compare the ease of joint R&R to the 4340's.
Most people into 'wheeling have seen these pictures a few times. I just had to take my own. It is easy to see in the pictures what the differences are between the 4340 shafts and the stockers, but you really don't gain full understanding until they are in your hands. These things are beefy!
This picture shows a couple things to look for when inspecting your axles. The
first problem is the shiny spots in the middle of the picture. This is caused by
not having the steering stops adjusted properly and allowing the axle joint to
bind. The axles themselves aren't bothered by this amount of damage, but the
bind puts incredible stress on the u-joints. This can be a major cause of
u-joint failure in many trucks. Most folks worry about tire rubbing when
adjusting steering stops. Make sure you pay attention to axle joint bind as
well. The second problem in this picture appears just above the seal ring. You
can see a series of parallel lines across the face of the bearing surface on the
axle. This is brinneling of the bearing surface most often caused by vibration
wear when the bearing surfaces don't move relative to each other or by a bad
bearing roller. The wear on this stub shaft only covers about a third of the
surface, so I am assuming it is from vibration. An interesting note: The stock
bearings in other spindles I've removed had the bearing rollers placed at an
angle to the axle, not parallel. Replacement bearings have the rollers parallel
to the axle centerline. I wonder if the stock bearings are angled to prevent
this wear?
If you look closely, you can see the snap ring buried in the pink grease on this
freshly assembled u-joint. This is another major improvement to the longevity of
these joints. The theory is that the stock circlips work their way out of the
groove which allows the u-joint cap to work out of the axle ears which causes
the joint to blow up. The full-circle snap rings are supposed to keep this from
happening. It was quite a shock when I first started working on these axles to
see how loose the snap rings are. The are only about 2/3 the thickness of
the circlips the joints come with. I found out that snap rings don't come in an
overabundance of different sizes either. The grooves in these joint caps were
1.080" ID. I bought some 1" snap rings which fit very snugly in the
groove. The snap rings I took out of these axles were somewhat looser. It was
hard to measure them since they had been distorted somewhat, but they appeared
to be 1.125" diameter. So far, I like the smaller ones better.
Here they are. Bright and shiny and ready for another season of wheeling!
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