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