Toyota 4WD trucks up through 1985 (in the US) featured 8" axles
front and rear, 8" rear axles continued at least through the '95
pickup and 4Runner.
The Toyota mini-truck solid front axle is designed with the
differential offset to the right hand side of the vehicle. This allows
the front driveshaft to pass beside the engine and transmission. One of
the consequences of this is that the right hand side spring perch sits
up on the side of the differential housing. In order to clear the
steering arm on the left side, Toyota chose to place the left hand side
spring perch closer to the axle tube, resulting in approx. a 3/8"
height difference between the two sides. To compensate for the height
difference, the stock front springs are asymmetrical, with the right
side having less arch than the left side, On top of that, since the
right side is flatter, this means it is inherently "softer"
than the more arched left side, so the individual spring leaves are a
made a bit thicker to compensate for the loss of stiffness due the the
Many aftermarket front springs also offer this different arch, but many
do not make the right hand spring stiffer. This results in a front end
lean. Since the spring perches are located approximately halfway out on
the axle, a small difference at the spring is magnified by at least a
factor of two at the wheel. However, with the stock steering and spring
setup, there's not a lot that can be done about this. However, if the
steering is modified to eliminate the interference problems of the
stock steering arm, then there is a simple fix.
Another problem on Toyota trucks that see a lot of off-road use is that
the stock spring perches can become distorted from the forces of
rockcrawling. The stock spring perches are a bit weak, and adding a bit
of support to them before they are damaged will prevent it from
A last problem with the stock spring perches is that they are only
about 4-3/4" long. With the spring over axle configuration, this
short perch can contribute to axle wrap. A longer spring perch can help
spread the axle torque load over a longer length of the leaf spring,
lessening axle wrap. Too long a perch and you can lessen the
flexibility of the spring.
So, there are a couple of issues with the stock Toyota spring perches
that can all be fixed at one time. To add some strength to the left
hand perch, I cut two pieces of 1/4" wall 2-1/2" square tube
and trimmed them to match the profile of the existing perch support.
These pieces were then welded to the axle and perch, extending the
length of the perch. Then I cut a length of 3/8" ax 2" flat
bar approx. 5-1/2" long. In the center, I drilled a 5/8" dia.
hole to accommodate the head of the center bolt on the spring and used
a spare center bolt to align the spacer to the perch and welded the
spacer in place.
It wouldn't do to have a nice beefy left hand perch and keep the stock
right hand perch, now would it? I cut two pieces of 3/8" x 2"
flat bar long enough to span the gap between the top and bottom
perches, and then welded them in place. To fill the gaps, I fashioned
pieces of 3/16" flat bar and welded those in place as well. This
boxed the whole perch and also extended it 3/4" in length. All in
all this project took me about half a day to finish and cost about $10
One potential weakness of the Toyota axles in extreme off-road use is
the drain plug located o the bottom of the axle housing. The plug is
required to drain the gear oil from the axle since there is no access
plate due to the 3rd member (dropout) design. The drain plug is a low
profile 24mm hex head bolt surrounded by a welded-on ring that affords
some protection that is suitable for mild off-road use. However, in
heavy use, the ring can get worn away or damaged from scraping over
rocks, the bolt head can get damaged to the point it is not possible to
get a socket on it to remove it, or worse yet, it can be knocked loose
by rock contact.
In light of these problems, one common fix is to weld the drain plug in
place. This prevents it from loosening up, but also makes draining gear
oil difficult. A simple fix for draining gear oil is to weld the nuts
onto the two lower 3rd member mounting studs (converting them into
bolts) and then simply remove those two studs to drain the gear oil.
This does leave a few ounces of gear oil in the housing but should
suffice for routine maintenance.
While the above fix does indeed cure the problem of losing a drain plug
on the trail, there is another problem. That is that the plug itself
and the protecting ring hang down below the axle and their sharp edges
can cause the axle to hang up instead of sliding over rocks. I suppose
in time, that excess metal would wear away, but how about giving it a
helping hand :-) After running welded plugs (front and rear) for a
year, and getting hung up on the differential housings one too many
time, I finally decided to do something about this.
So, first step was to mark out an area of the existing housing to be
removed. I settled on 3" to each side of center, which put the cut
just beyond the drain plug but before some inner bracing inside the
axle housing itself. I used a plasma cutter to make the rough opening,
then a grinder to smooth and square up the edges. I removed the lower
two studs while working on the axle and also kept some water in the
housing to catch debris and soak up the heat. An abrasive cutoff wheel
would also work for this step of the process.
Next, I cut a length of 1/4" x 4" hot rolled flat bar
7-1/4" long, then put a pair of 30° bends in it, 1.5"
from the center. This allowed the plate to conform to the curvature of
the housing. Then, the opening in the housing was slowly ground out to
accommodate the plate, which is designed to sit flush to the back side
of the 3rd member mounting flange. Since it projects over the back side
of the housing, that part was trimmed 1/4" below the mounting
flange and matching angles for the plate were formed. With the plate
flush to the flange, the two lower stud holes are left clear for use in
draining gear oil.
Here, you can see how the plate fits on the back side of the housing.
Take you time to slowly enlarge the opening and constantly check the
fit and grind down any obstructions until the plate fits down snugly
inside the opening. I spent about an hour fitting the plate into the
opening. Once in place, I beveled the edges in preparation for welding.
I used 1/8" 7018 low hydrogen welding rod with DCEP at about 130A
and slowly worked my way around the plate, making short beads on
alternate sides. I kept water in the housing and also used wet rags on
either side to soak up heat.
Once the plate was welded around the edges, I grooved the top side of
the 3 projecting pieces of the plate, hammered them down over the
bottom edge of the housing and filled in around them with weld bead.
Then I fashioned another piece of 1/4" x 4" flat bar about
3" wide, with two slight bends to conform to the front of the
housing and welded it in place, trimming the excess to add a
reinforcing plate to the front of the housing. The stock axle housing
is about 6mm thick (~1/4") combined with the additional 1/4"
plate gives a 1/2" thick piece of steel up front to fend off
rocks. The clearanced bottom of the axle sits nearly 1" higher
than the lowest points of the stock axle (this is almost like going up
2" in tire diameter without needing any lift or gearing changes),
but more importantly, the bottom of the housing is smooth as a baby's
bottom so to speak. There are no sharp edges to catch on rocks, no
drain plugs to get knocked out, just a nice clean and smooth underside.
For protection, I wire-brushed the bare steel, cleaned it with an acid
etch and zinc phosphate rust converter then top coated it with POR-15
primer followed by Chassis Black.
The normal Toyota steering setup places the tie rod below the front
springs. This is fine until you get into large rocks and then the
flimsy tie rod is vulnerable to damage.
Even my hybrid Toyota/Dana60 axle kept this same arrangement. Even
though the tie rod is higher than stock, it still showed scars of close
encounters with rocks even after a fairly easy run up the Clawhammer
trail in Johnson Valley. So, something had to be done about that...
First I found a scrap of steel, 3" thick and about 8" dia. at
the local steel yard. Cost $7.80 plus tax, bargain of the century!
First step was to whittle 28 lbs. of steel into some useable blocks. I
trimmed the ends of the block to 6" long then 4" wide...
Finally, the block was sliced in two making a pair of 2" x 3"
x 6" blocks, about 78 square inches of steel cut on my 4x6 bandsaw
in about 2 hours! Next step was to bevel the top surface to 9-10
degrees to match the kingpin angle on the steering arms. I used a
homemade flycutter with carbide bit with the milling machine head
tipped to the needed angle. After milling the blocks were welded to the
Next, 5/8" holes were bored for the draglink and tie rod ends to
bolt into. These holes were drilled perpendicular to the beveled
surface. This was done to ensure the rod ends would be operating at
minimal angles for better strength. I retained the existing tie rod
bolt with a solid spacer to add strength along with 3 allen bolts on
Also, I took this occasion to improve my steering performance. As
designed (to keep the tie rod from hitting the differential housing),
the steering arms placed the draglink end farther away from the kingpin
than the pitman arm length. This resulted in less than lock to lock
steering and a greater turning radius. I moved the drag link in about
1/2" less than the pitman length to ensure lock to lock steering
even at full droop. I then moved the tie rod in closer to the kingpin
enough to clear the draglink and to get it closer to the axle housing
(see the reason later on).
And here is the finished product. Tie rod is tucked up above the
springs with the draglink, safely out of harms way.
After fitting everything up, I added top brackets for each rod end,
placing them in double shear for added safety. I then used a high
temperature ceramic paint and baked it on in an oven for a good durable
Cost for the project was $8 for the steel, a pair of bandsaw blades
@$18/ea. (I was using a 0.035" thick blade and that was too much
for my little saw, I now run 0.020" blades and they work much
better) a bit of cutting oil, some paint, oh and $1700 for the milling
machine (I think I'll be able to use that on some other project) and 2
days in the garage and driveway!
So, besides raising my tie rod out of the rocks, my other reason for
going to HySteer, was to get the tie rod up closer to the top of the
axle housing. Why you ask? Well, it makes it a lot easier to connect
things to the tie rod, you know like steering stabilizers or hydraulic
rams, that sort of thing...
I went with a hydraulic assist steering setup from All Pro Offroad. The kit utilizes
parts from Howe Racing Equipment
including a new high volume power steering pump, modified Toyota IFS
steering box and of course the hydraulic ram itself. The basic idea of
the system is quite simple; two new ports are added to the steering box
to feed hydraulic fluid under pressure from one port to the hydraulic
ram and allow fluid to return from the other side of the ram to the
steering box. The steering box continues to function normally,
providing approx. 60% of the steering force. The ram applies the rest.
So, on with the upgrade...
First step is to remove almost all the stock power steering components.
The only stock part re-used is the idler/tensioner pulley and bracket
and the v-belt. I removed the pump, its bracket, the reservoir, the
high and low pressure lines and the old steering box.
Next, I fashioned a mounting bracket out of some 2x2x1/4" square
tubing. This was cut to a "U" shape, drilled for the ram end
bolt and finally welded to the top of the axle housing. I used 3 passes
of 7018 welding rod at about 140 amps to get good penetration and build
up a good fillet weld. I added a front brace for added support. Next, I
turned some brass bushings to fill in the 1.5" ID of the bracket.
Shown is my initial bushing, 1/2" on each side, but later I made
the front bushing 1/4" and the rear 3/4" to keep the ram
closer to the tie rod to minimize the angle. This is the main reason
for the tie rod relocation I did in the HySteer conversion, above.
Next, time to start installing the new power steering parts. A new Howe
pump is installed in a new bracket. I installed the new steering box
using the existing bolts and mounting holes. I found the new valve on
the steering box is longer than on the old box. This pushed the splines
on my steering shaft way up, luckily the 3" body lift I had had
pulled the shaft out a bit, so it ended up just barely fitting.
When re-installing the pitman arm, be sure to line up the scribed lines
on the arm and sector shaft (see image below-left). Then turn the
steering wheel to straight ahead and install the steering shaft.
After connecting all the parts, its fairly easy to align the steering.
I clamped two straight edges on each brake disc, the adjust the wheels
for toe in by measuring across the front and rear, I used about
1/8" toe across the 3' bars.
You can also sight down the bars (or tires) to set the draglink to
straight ahead and centered by lining up the tread on the rear tires
equally down each side. You can get remarkable good readings this way.
Afterall, figure you have approx. 8' between the front and rear tires.
At that distance, a 1" difference in where the left and right
tires line up with the rear tires is equal to an error of 0.6 degrees.
You can easily eyeball the alignment to 1/8"and that puts you
within 1 minute of arc. Who needs a $10,000 computerized alignment rack
when you can do as good with your eyeballs and a tape measure.
Important note: You should re-check the toe in with the
tires on the ground after doing the above. Easy enough to do you
putting a mark around the circumference of the front tires and then
measuring the front and rear width off that mark. Sometimes the weight
of the vehicle will deflect the wheels inward at the top and that ca
slightly affect the toe. Also helps to roll the vehicle back and forth
a little to get things into the normal orientation and release any
stress from jacking the front end up and down. If you do notice a
change in the toe measurement, make a note of the amount of change and
then you can take that into account next time. For example if you set
1/8" toe in in the air then measure 1/8" toe out on the
ground, you know your front end changes 1/4" with weight on it. So
next time you need to align it, set it to 1/8" + 1/4" (or
3/8) toe in. Then with weight on it, the tires should push out the
1/4" and you'll end up at approx. 1/8" toe in.
By putting all parts at their centers, I found my steering wheel was
level, I got rid of the steering pull I used to have, vehicle tracked
dead straight ahead, and I even had a bit of return to center despite
the hydraulic assist ram :)
Now, what about camber and caster you might ask? Well, camber is pretty
much set by the axle housing. The two knuckle (or trunion) bearings,
drop into recesses in the steering knuckles and that sets the camber.
There are purportedy eccentric knuckle bearings available in Australia
that allow a small amount of camber adjustment by having the center
hole in the knuckle bearing offset a bit from center. As imagined, you
would not be able to get more than a degree or so of correction from
something like that. For caster, that is fixed by the relationship of
the spring perches welded to the axle housing and the relationship of
the leaf springs to the frame. So caster can be changed by either
modifying the perches on the housing or by adding a steel shim (or
wedge) between the springs and axle/perch. You can find more about that
and also how to get a rough measure of caster on this web page...
Here's the finished product. Steering parts tucked up safe from trail
obstacles. Ram is in-line with the tie rod and works marvelous on and
off-road. Even with aired down 15" wide tires at a dead stop, its
easy to palm the wheel from lock to lock. On the road, it takes a bit
to get used to the *very* light steering touch. Steering is precise,
absolutely no backlash, there is a tiny bit of road feel. Its very
light but once you get used to it, it feels normal.
On a recent 3-day trip across the Dusy/Ershim trail the
ease of steering was very nice, lots of tight turns between trees and
around rocks. After 6 hours on the trail, there is no fatigue, this is
real power steering!
After a year of running a clearanced front axle (and stock rear axle)
and finding out how much of a difference it made (read: front easliy
clears trail obstacles only to get hung up on the rear axle), it was
time to do the rear axle. I had been planning some other rear axle
upgrades including swapping my narrow '85 rear axle for the wider
IFS-style rear axle. After stripping down the housing, it was shaved of
the drain plug and lower part of the housing. A 1/4" steel plate
was welded in place and ground smooth:
You can see in the image on the right the bottom part of the axle that
was removed and the smooth piece that replaces it. On the rear axle the
ground clearance is only increased about 3/4", but the more
important benefit is the reduction in drag, there is nothing to get
hung up on rocks.
As part of the rear axle upgrade, I decided to go with a full floating
rear axle. A full floating axle is stronger as the axle shaft only
transmits torque and the axle housing (and spindle) carry all the load.
After years of fighting with bent axle shafts and inadequate wheel
bearings, this was an important point for me. Also, the Front Range Offroad Fabrication
full floater kit I chose to use, had disc brakes, which would be a big
improvement in braking over my small drum brakes. The kit was very well
thought out as it also included an adjustable proportioning valve to
replace the troublesome stock Load Sensing Proportioning Valve (LSPV)
as well as using disc brakes with integral mechanical parking brakes.
So at long last, got the axle built and installed in the summer of
In picture A, above, you can see the overall rear setup. The 3"
wider IFS rear axle housing is shaved and plated with a high clearance
axle kit. Picturedalso are the original Rancho 9012 shocks, those
have since been changed to longer remote reservoir Ranchos. Still
working on getting those shocks dialed in and positioned.
In picture B, you can see the detail of the Supra rear disc brakes and
brake line plumbing. I ran the hard lines under the springs and behind
the u-bolts and fashioned a bolt-on plate to protect them from trail
damage. Then Earls brake like fittings were added to transition from
the hard line up to a length of s/s flex line used in place of the
rubber line supplied in the Front Range.kit. Since the Supra calipers
are essentially mounted upside down on the F/F axle, you need to unbolt
them and roll them to the front of the axle to bleed. I did not like
the way the supplied rubber hose handled that, so went to a slightly
longer s/s flex line.
In picture C, you can see the the block off plug I added up front to
eliminate the stock LSPV valve, which is no longer used. In back, where
the LSPV used to be, the line from the brake m/s up front connects to
the brake line to the axle. Then the line that used to run from the
LSPV to the front brake circuit (for the Bypass function of the LSPV)
is plugged. For folks wanting to do a similar LSPV elimination and/or
disc brake line install, all parts are available from 4Crawler Offroad.
And finally, in picture D, you can see the end result, locking hubs on
the rear axle. I originally installed some FJ-80 drive flanges and do
carry those as spares. But, to beef up the stock Aisin hubs, I
installed a set of Longfield cro-moly hub gears and also a set of ARP
hub studs. Should make the rear axle pretty stout with that and the
cro-moly axle shafts in the full floating setup. And yes, the rear hubs
do work. Lock up the front hubs, unlock the rear hubs and slap it in 4H
and you have instant FWD. Kind of different driving now in FWD that I
was used to with the stock front axle. With the stock front birfield/CV
joints, you have a very smooth front axle drive, even while turning.
Now with the u-joint D60 outers, it is VERY lumpy while turning. Feels
like something is broken, badly. But once you straighten out the
wheels, it is fairly smooth. And with the soft rear springs up front,
you get a lot of front lift when you accelerate. When I had used FWD
before with my original stiff lift springs, I found it was a lot better
behaved compared to now. But the idea was not to have a FWD truck,
rather one that is more reliable off-road.
And so far the driving results on and off road have been great. The
biggest change is that it drives smooth on pavement. I had been
fighting bent rear axle shafts for many, MANY years on my old '85 axle.
I think I had between 6 and 8 axle shafts and all were bent to one
degree or another. Was interesting watching the truck on the smog test
dyno, it was hopping all over the place. Now, with the full floating
axle spindles and double bearings (just like the front axle), it rolls
like it is on glass. And off road, it just works like normal, except
now the axle is wider, the housing is shaved for addded clearance, and
it has mounts for a sway bar (with disconnects) so it just works better
[Last updated: 01.May.2019]