Axle Housing Upgrade

Stock Toyota axle housings are fairly stout units.  The axel tube walls are nearly .220 and the later years featured a hefty truss running along the bottom from the factory.  The weak link appears to be the long side axel tube.  Several of the BTG club members have bent 3-5 housings each, mainly due to high speed driving or jumping the rig.  The sure sign that the tube is bent is the inability to remove the birfield from the knuckle. The bend is also typically visible, occurring between the spring perch and axle ear.  Some of the guys in the club cut some axel tubes off of some of the bent housings and discovered a weak point in the tube where the tube ID is opened up to allow the knuckle to be pressed in.  Unfortunately a small section of this thinner wall is left even after the knuckle is pressed in.

In the picture above you can clearly see the machined section of the axel tube.  It doesn't seem like much but if the housing is going to bend it's going to be at the thinnest point.  The inability to truss this section externally doesn't help either.

You may be wondering how that axle tube was shredded.  The picture is from Mark Mason's Toyota and the damage is from the Trucking Nationals.  He jumped the truck and landed hard, hitting  a 3 foot high concrete wall.  The knuckle was ripped right out of the tube.  The first picture above shows the temporary fix to get the wounded buggy back on the trailer.  The second picture shows the passenger side, note the axel shaft is no longer lined up with the axle tube seal. 

The plan for beefing up the axel housing was pretty simple.  Basically remove the existing tubes to re-use the center sections, then install bigger diameter, heavy walled DOM tubing.  The first hurdle involved the knuckles themselves.  Cutting them off of the old housings was easy but we also had to come up with a way to clean up the ends so they could be turned down to the proper diameter to allow them to be pressed into the new axle tubes.  I came up with the above fixture that locates the ear via the oil seal and then the knuckle is clamped to the fixture on one end.  The other end can then be inserted into the chuck on a lathe.

Here's the completed fixture with the knuckle attached spinning in the lathe.  I only had to take a little bit of material off the diameter along with cleaning up some of the left over weld.  the second picture shows the cleaned up knuckle.  I left the step on there for strength, if you look inside the knuckle you'll notice the ID gets bigger under the step so turning it down would have weakened the part.

The next hurdle is the biggest one, we needed some way to accurately locate the third member installed on a center section in relation to the knuckles.  It also had to be rigid enough to hold these parts in place while they were being welded.  Thankfully Mark and Larry had designed and fabricated a Toyota axel jig originally intending to use it to cut and turn knuckles to adjust the caster.  Mark modified the Jig by drilling and tapping locating holes in the 3 fixture pieces.  Then the fixture pieces were installed a stock housing, the center bar was inserted thru all three fixture piece and finally the locating holes were transferred to the center bar.  As you can see above, once the jig is assembled, the knuckles are accurately located in relation to the center section.

The last modification to the jig was an access hole to get to the center locating screw.

Now it was time to cut up our bent housings.  To save me some time Mark was going to cut the axel tubs off of mine while sparing the axel truss and hydro cylinder mount.

Here's a shot of Mark cutting the section of axel tube that was under the truss.  You have to love plasma cutters.  Marks housing was a bit simpler since he only needed the center section.

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