The HSC 60 Knuckles are absolute works of art.

They are designed as replacement knuckles for Chevy/Dodge style Dana 60s.  You can see from the pic the 6 bolt non-concentric GM spindle bolt pattern, and the semi-circular "indentation cutout" (arrow0 for the large single piston GM/Dodge style brakes.

Massive chunks of cast Nickel-chromium-molybdenum alloy steel.

DO NOT confuse the term "cast" here - it is not short for "cast iron" as it is so frequently used, it has nothing to do with the material - it is the process by which the material is made into the useful shape.

This is very important, because WAY too many people misuse the term, and will be heard saying things like "I prefer steel to cast, because a cast part like that will just crack/shatter when it breaks, whereas the steel will bend"

This is, of course, a gross misunderstanding of the facts, and is completely erroneous.

The knuckles will physically fit on Ford axle end forgings (inner knuckles or C's).  But the user would have to swap to GM parts or go custom with:

• brakes
• spindle, wheel bearings, and hub
• stub axle

Of course, this may be an ideal upgrade anyway, if you're swapping to 35 spline Cr-Mo axles at the same time, since you can just swap to Chevy stub shafts.

The material is ASTM A487.   Nickel-chromium-molybdenum alloy steel.  The equivalent SAE 4 digit code for this material that we are more familiar with would be 8630.

That means it's like the chrom-moly alloy steel we are more familiar with - but with the addition of Nickel as a further alloying element. 

The exact specifications are as follows:

• Tensile Strength 105-130,000 psi
• Yield Strength 85,000 psi
• Brinell Hardness 235
• Percent Elongation 17%

Perhaps a quick review of alloying elements is required:

• Chromium Increases corrosion resistance, hardenability and wear resistance
• Molybdenum Deepens hardening, raises creep strength and hot-hardness, enhances corrosion resistance and increases wear resistance.
• Nickel Increases strength and toughness

Here are some yield strength numbers for comparison, taken from Taken from the 24th edition of the Machinery's handbook, table 9 - Typical Properties of Selected Carbon and Alloy Steels.

1030 being a typical plate steel.

Recall that Yield Strength is the point at which a material exhibits a strain increase without increase in stress. This is the load at which a material has exceeded its elastic limit and becomes permanently deformed.

1030 normalized 50,000 psi, annealed 50,000 psi, quenched and tempered (1200°C) 64,000 psi

Comparing the numbers for normalized, we see 50kpsi vs 85kpsi - that's a 70% greater yield strength!

It's clear then that this is a vastly superior material to the plate mild steel or nodular cast-iron that other alternatives are constructed from.

The casting also produces a product with an even, consistent surface finish that is extremely important in preventing stress raisers at the surface.  Remember, stress raisers lead to the formation of tiny cracks that will eventually lead to fatigue and failure of the part.

In addition, these knuckles can easily be welded, whether for customization or emergency trail repair (like you're ever going to need that!).

So we have so far, a part that is superior to all other in material and manufacturing process, but what about design?

Most notably, there is the huge increase in strength and fatigue life created by the increased web and flange thickness.  A stock Chevy Dana 60 knuckle weighs approximately 16.5 pounds. The Crane knuckles weigh approximately 22 pounds.

When material, process, size and shape are all taken into account it is extremely reasonable to estimate that these knuckles are at least twice as strong as stock knuckles.

But by far the greatest innovation of the Crane knuckles is the integrated high-steer indexing system.

There is a raised indexing tab cast into the top of the knuckle.  This allows for use of a matching slot in the underside of the steering arm.  If the parts are fit together closely enough, this ingenious system relieves the fasteners of the shear load caused by steering forces.

The idea is so simple yet brilliant, it leaves the rest of us smacking our heads and muttering "Why didn't I think of  that?"

More on the closeness of fit and steering arms later on.

Continuing in the theme of excellent, innovative features that prove that Crane not only listen to customers needs, but as wheelers themselves understand what we want, the Crane knuckles have this excellent feature:

Dual steering stops, as indicated by the arrows.  This allows not only finer tuning of turning angles, which is critical with hydraulic steering and big axles/U-joints (like my Superiors and CTMs), but also a stronger steering stop system, as two sides will be working together to prevent further turning at full lock, in either direction.  This is again critical with powerful hydraulic steering, and is key to preventing binding and possible destruction of axle yoke, U-joint, and knuckle itself as happens when the knuckles are over-steered.

Here's a shot of the complete knuckle and steering arm package from crane. 

The knuckles and steering arms are shipped uncoated, and must be painted or otherwise coated prior to assembly and installation.

I used a 2 step process that has worked well for me before (and that is all rattle-can - no painting gear needed).

Step one is to prime the raw steel parts with a high quality zinc rich self-etching primer.  Not to be confused with cheap grey primer - this stuff is 2-3x more expensive but is the only stuff that will properly adhere to the raw steel.

The Crane knuckles also use 9/16-18NF threaded holes for retention of steering arms / upper kingpin caps. 

Assuming a grade 8 fastener, this represents an increase in available clamping force of about 300 ft/lbs, an increase in maximum tightening torque capacity of 30 ft/lbs and an increase in shear strength from about 23,500 lbs to 29,800 lbs, or 21% per fastener.

However, the Crane knuckles are available in "classic" form, with stock Chevy location steering arms and stock 1/2-NF threaded holes for the kingpin cap bolts/studs.

These "classic" 60 knuckles from crane also do not feature the high-steer indexing system, and can easily be used with any existing dana 60 High Steer Arm.

Here we see the basic design of the arm.  The arms are machined from a single piece of mild steel that is initially 1 inch thick.

They fit over the kingpin bushing and spring, and have a separate cast aluminium cap.  The attachment holes are straight-cut holes for 9/16" bolts.

They have an angle machined into the steering arm, that is intended to allow the "cancellation" of the stock kingpin inclination angle, resulting in a horizontal surface for the steering linkages rod end attachments.  The theory is, that by doing so, regardless of whether the steering linkage uses Heim joints or standard automotive tie rod ends - by having the steering arm horizontal at rest, the least amount of valuable misalignment angle available in the joint is consumed in it's static mounting position.

This in turn would leave the greatest amount of misalignment angle available for accommodating suspension travel without binding the steering linkage.

The theory is sound, and a good idea, but the problem is, if you do this, BOTH sides of the steering arm must remain parallel to one another - which they do not in the Crane arms. This is because the head of the bolt and the nut must be parallel to one another, you can't have either trying to seat against an angled surface (in the case of a TRE, the tapered stud and nut must be perpendicular to one another - the result is the same) and therefore  - the 2 sides of the arm must be parallel.

If you machine an angle into one side of the arm, as in the Crane arms, you have to cut a slot for either the nut or the head of the  bolt.

This is what I had to do mount the arms, but is not a particularly good solution for 2 reasons:

• The removal of material and therefore potential weakening of the arm, right where the concentration of stress is high and you want it to be strongest.  In order to have parallel surfaces for nut and bolt head, the slot has to be cut to a depth equal to the thinnest part of the arm - which is only 5/8"
• You can't properly machine the slot yourself unless you have the proper machine tools.  This complicates the matter slightly from just having to bore the correct diameter hole.

The much better way to eliminate the stock kingpin inclination would be to start with a much thicker piece of steel and mill both sides the same angle, eliminating the angle, but leaving full thickness (an inch or so) and both sides of the arm parallel to one another.

If it were determined that this approach would involve too great an expense in material and time, personally I would much prefer to simply have flat 1" thick arms, rather than having them 5/8" thick around the hole and having to mill a slot.

There is one neat benefit to the "machine slot" approach though - you can machine the slot just big enough for the bolt head and then not require a tool on the head of the bolt during assembly or disassembly.

Finally, the machined angle presents one last potential problem area.  And that is the very limited thickness left in the arm, right were the indexing slot overlaps the arm where it is angled (yellow arrows). 

Unfortunately, this happens right where there is a major section change from the "body" of the arm to the arm itself.  As it is, this will be a highly stressed area as the steering forces attempt to try and twist the arm off here.

The result is, the machined angle leaves one side of the arm just 5/8" thick, and then on top of that, the indexing slot in the arm removes even more material (I forgot to get an exact measurement, but it's probably about 1/4" deep) leaving the arm only about 1/2" thick at the thinnest part.

We shall see how they hold up, but this doesn't seem enough for my tastes, and the prospect of a steering arm failure on the trail is not a thrilling one.

Installed on the knuckle the arms look like this.

This side looks just the job...

As for retention, the arms themselves are retained with four 9/16-18NF fine thread SAE grade 8 bolts and lock washers.

The 9/16" bolts are an upgrade in size from the stock 1/2" fine thread, but the straight holes in the arm and separate cap result in a lack of a true zero-clearance fit for the fasteners.

Without either tapered nuts (as in stock D60 hardware) or tapered, split cone washers (as in D44 style hardware) there is a possibility of loose fit around the fasteners, leading to relative motion between arm and knuckle, fatigue, and possible bolt failure.

So in summary, we have:

Advantages:

• Brilliant indexed system - exactly what a joint of this nature should have.
• Beefy 9/16" sized hardware
• Cool cast aluminium cap
• 1" thick steel "body"

Areas for improvement:

• Index system fit should be tighter - a true interference fit
• Arm itself should be no less than 1" thick at its thinnest point
• If inclination cancelling angle is to be used, it should be machined into both sides, so arm isn't thinner on one edge and so that bolt head and nut are parallel.
• For optimum design - fastening system should incorporate studs and some sort of tapered fit (washer or nut seat)

Overall a good first design from Crane, with an innovative and extremely useful indexing system, that could use some refinements.

*** BREAKING NEWS ***

Here's the really cool thing - I shared all of these initial opinions of mine with Tim Plamondon, one of the key players at Crane High Clearance (who is, incidentally, a fourth or fifth generation pattern maker [that's a dude who makes things from molten steel!], a heck if a nice guy to talk to, with a keen interest, super technical ability, and great customer service)

I also shared with him a few other observations and design ideas I haven;t yet published here, as he has agreed to work with me in designing and developing the ULTIMATE D60 high steering arm, one that can truly take it's place beside their great knuckles.

Stay tuned - I will post results, impressions, and more testing here as the project progresses.

Here's a little something I, as usual, didn't anticipate.

I have a "custom" front brake setup on my front Dana 60.  Instead of the stock brakes, I use a 3/4 ton calliper and rotor, that requires a custom calliper bracket.  This custom bracket is really nothing more than the grafting together of 1 ton and 3/4 ton brackets.

However, because if the extra beef of the Crane knuckles, at assembly time, I found my custom bracket would no longer fit flush against the spindle, due to slight interference as indicated by the arrows in the pic at left.

I just had to take my 4.5" mini grinder and "tidy up" the knuckle just a tad.

You know, I discovered you really don't know what kind of (wo)man you are until you have to take a grinder to almost $1k worth of brand spanking new chrom-moly knuckles!!

But it was really just a very light smoothing, and I should emphasize, certainly no fault of the Crane knuckles.

If you have stock 1 ton brakes, everything will fit like a glove, no grinder required!

But if you do have some sort of custom brake setup - you should be aware of the possibility....and prepare yourself psychologically :-)

Here we can see everything is tidied up nicely and I'm back in business.

Custom brakes fitted up, big fat Cr-mo knuckles, axle shafts, and U-joints

Ohhhh yeaaaa baby!