Check out our new YouTube videos on the idler arm upgrade:
If there was a "weak link" in the Toyota IFS Hilux pickups,
4Runners, and T100s, that would be the steering system. You can see
below that it is a fairly complicated system with lots of moving parts
and joints. One of the most highly loaded components in that system is
the idler arm and it's operation is described in the paragraph
following. Folks often ask if cranking up torsion bars or installing
ball joint spacers or adding this or that sort of lift will cause
increased wear and tear on the steering and idler arm. Actually the
short answer is not really, but the longer answer is it depends. One
likely reason for installing the lift is that you may be considering
taller and/or wider wheels and tires. And you may be considering the
lift and larger tires in order to either go off-road or to handle more
challenging off-road driving. And with the lift and larger tires and
harder off-road driving you may end up doing, that will put more wear
and tear on the steering. So did the lift cause the steering wear or
A typical Toyota 4WD IFS steering system is pictured below. The
steering wheel and shaft connect to the steering box (8). The pitman
arm (9) connects to the sector shaft (10) on the bottom of the steering
box and transfers steering input to the center link or relay rod (6).
The relay rod connects to the idler arm (3) on the passenger side. To
the ends of the center link are tie rod ends (2 and 4/5) that connect
to the steering knuckles on each side of the front axle to turn the
wheels. A steering stabilizer (7) attaches between the frame and center
link to dampen jolts from the road. Of all these parts, only the idler
arm and steering box are re-buildable, but the idler arm seems to take
the brunt of the abuse and is the most common part to require repair.
If you are tired of destroying stock plastic idler arm bushings, these
bronze bushings are machined to exacting tolerances in order to provide
maximum strength and life. They are very hard and durable. As a result,
not only can they bear much more load and resist wear, but they also
transmit much less shock to the steering wheel making the truck easier
to handle on rough roads.
One way to look at the purpose of the bushings on the idler arm is to
imagine holding up a flag on a pole. If you only use one hand to hold
the flag pole, it puts a lot of stress on that one hand and it is hard
to hold it straight. If you use two hands separated by a distance, the
load is more equal between your two hands and you can hold it straight
a lot easier. WIth the stock plastic bushings, you have the idler arm
set up more like the one-handed setup, since the bottom bushing can
give under load letting the idler arm twist inside the housing. Now
with the two bronze bushings, the shaft is held solidly and the forces
are transferred along the shaft to both bushings more equally. Now
there is a limit to the ultimate bending strength of the steel shaft
and if you put enough load on it, it'll bend no matter what sort of
bushings you use. The bigger the shaft, the stronger it is, given
similar material. So the bushings are designed to fit the largest
diameter shaft available in aftermarket idler arms.
One consideration of a machined bronze bushing is the need for tight
tolerances in order to fit over the shaft of the idler arm and inside
the housing of the idler arm bracket. Unlike soft plastic that can be
squished into a too-small hole, the bronze bushings require a precisely
sized hole and shaft for a good fit. We measured numerous idler arms in
search of the strongest and most affordable to support. Luckily for
you, we found both in some commonly available idler arms:.
Any other questions not covered here, send us an e-mail
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Good question! There are two main reasons but before getting into them
it is important to point out that 1st and 2nd gen idler arms are
interchangeable. The second gen arms are typically stronger though.
Therefore, if you have a 1st gen truck, it make sense to install a 2nd
gen arm for the added strength.
First, for the most strength, the largest shaft diameter is the key
factor. Initially we assumed that we would want to at the very least
produce idler arm bushings for the high-end Napa arm as well as the OEM
arm because we assumed they would be the best. After an idler arm
spending spree we found some interesting things we'll discuss below.
As you can see, the arms with the largest shaft diameter are at the top
of the chart. And that larger diameter equates to almost 11% increase
in stiffness over the OEM part, since the torsional stiffness increases
by the 4th power of the diameter. Another interesting note is that the
Napa 1032403 which has a diameter similar to a 2WD OEM arm is also sold
for 4WD trucks even though from a strength standpoint, this arm is
below spec., in fact it is about 25% weaker than the FA5040 arm.
We also wanted to support shafts with high manufacturing quaility, such
factors as fully machined surfaces. Some of the shafts are only
partially machined. A stretchy plastic bushing can be jammed in place
with no problem, but this makes fitting a rigid bronze bushing
impossible. The part of the shaft closest to the arm itself wears more
than the rest. This means that a bushing that fits snuggly over the
lower part of the shaft will not fit at all over the rest of the shaft.
Assuming one was to verify that the shaft has a uniform diameter, there
is the issue of calibration. My calipers might not measure out like
yours. As a result it is difficult to machine the parts to order due to
the tight tolerances in this application. To reduce part cost it is
necessary to produce many at once and supporting one arm helps us
accomplish this goal.
Given these issues we have decided to support the most affordable yet
strongest idler arms.
(*) One thing to beware of is that sometimes, you'll get an arm in a
box marked "FA5040". But be sure to check for a genuine
FA5040 arm before taking the box out of the store. The genuine item is
marked with a single "L", as noted below. The genuine arm is
also in a nice shiny black clean finish. The imitation
"iak9424" arms are in a rough dark gray finish, like they
were taken directly out of the sand mold and into the box.
If you see a "555" stamped on the idle arm
itself (click here for a picture
of the stamping), that is likely a Sankei 555 arm, which is
actually a smaller 2WD arm. If you find a "555"
stamp, take that arm back and swap it for a genuine FA5040 arm. And you
might want to be wary of on-line sellers, like on eBay, as you'll not
be able to inspect the arm until it is shipped to you. If it is the
incorrect part. you may be stuck with shipping it back for an exchange.
Also, some Duralast FA5040 arms have a casting mark of "iak9424 L (click for picture of
stamping)" instead of the plain "L" on the genuine FA5040 arm (click for picture of
genuine FA5040 arm). The Pro-Forged arm also has "YN130"
stamped onto the top of the forged arm section. This "iak9424 L" arm has an
undersized shaft, comparable in diameter to the 2WD arm and appears to
be a lower quality part. So be sure to check for that when you get the
arm. Best bet is to pick one up at your local FLAPS where you can open
the box at the counter and verify you are getting the genuine article
before leaving the store. Note that some parts catalogs list a Duralast
FA1739 arm for certain model years. This arm while the same overall
mounting dimensions as the FA5040 arm, has a lower quality casting and
the arm shaft diameter is poorly machined meaning that it is difficult
to get the bronze bushings onto it. So ignore the parts catalog
recommendation and go with the FA5040 part. And this also applies to
the Napa-ATM-103-2403 idler arm, if it has just the "L"
casting mark, then it is likely the "good" version,
otherwise, it is likely a version with a different diameter shaft. THe
only way to know for sure is to remove the shaft and measure the
(**) The Pro-Forged idler arm has the larger 20mm dia.
shaft, this is a good thing. This shaft is made of 4140 heat treated
Cro-Moly steel and is thus extra strong. However, the inner diameter
(ID) of the bushing seats in the "L" cast housing is a bit
smaller than the FA5040 arm. Two options are to use a Dremel with a
sanding drum or grinder wheel to remove a few thousandths of an inch
from inside the housing until you can fit the bushing in place. Or we
can custom machine the bronze bushings to fit that housing for an
additional cost. See below for ordering options on bushings and idler
arm kits. Now there also appears to be a new model of this arm that
lacks the "L" in the casting, but instead has a threaded hole
for a grease fitting where the "L" used to be. This arm
housing has the same bushing seat ID at the original FA5040 arm and
thus will accept the regular bronze bushings, although you may need to
do a little touch up sanding on the ID of the arm housing to clean up
any burrs. So you can order those or you can order our
"Pro-Forged" bushing kit and specify you want the full size
bushings and we'll add in a grease fitting that fits the hole in the
arm housing. Or if you order one of our Pro-Forged
arm kits, we'll throw in the grease fitting, which Pro-Forged
sometimes omits. Unfortunately we can't guarantee which arm you'll get
as they both have identical part numbers and what shows up in our order
is what we have to work with. So if ordering a Pro-Forged arm from
another supplier, best advice is to wait until you have it in hand then
see if you have the "L" casting or the grease fitting hole
befre ordering bronze bushings. We are simply reporting the findings of
our product research and trying to pass that on to our customers.
Pro-Forged also lists a 102-0052 model arm for some model year trucks.
If anyone has had a chance to measure that one, let us know the arm
diameter. The listing has the same photo as the 102-0045 arm, so it may
be an identical unit, if so, it will likely work with the bronze
So the bushings are built with an inside diameter (ID) of approx.
0.787" (20mm) and an outside diameter (OD) of 0.941"
(~23.9mm) to fit over the idler arm shaft and inside the idler arm
housing. So the acid test is to measure the diameter of the shaft
inside the idler arm, and you need to take it apart to do that. If you
lack a micrometer or calipers to do that, wrap a piece of paper or
masking tape around the shaft then slice that where it overlaps. Take
that paper or tape off and measure the length, a 20mm shaft will
measure just short of 63mm long, a 19.5mm shaft will measure just over
Now if you are stuck with an idler arm with the smaller 19.5mm diameter
shaft and want to use the idler arm bushings, there is an option. You
can obtain some brass shim stock of the appropriate thickness to make
up the different in diameter between the shaft and bushing. We can
supply such shim stock if desired. It can also be ordered with the
bushings if you are unable to check the size of your idler arm shaft
prior to ordering. The piece of bushing stock will be cut to ~60mm wide
to roll into a ~20mm dia. circle and will be approx. 6" / 150mm
wide to allow it to be trimmed down (with scissors) to just fit from
the top to the bottom of the idler arm housing. This way the coiled up
shim stock will sit inside the housing and bushings and the shaft will
fit down inside that shim stock. This should allow most of the
0.767" / 19.5mm idler arm shafts to fit. You may need to do some
light filing/sanding of the housing to fit the OD of the bushings if
needed. We can supply either 0.009" or 0.004" shim material.
The 0.009" shim will make up the 0.5mm difference in one layer,
the 0.004" will include enough material for 2 layers, giving
flexibility to handle shafts slightly over 19.5mm. Either piece of shim
stock is US$10.00 plus postage or $9.00 additonal when ordered with the
bushings, specify your thickness preference in the Special Instructions
to Seller section of the order form.
As described above, no. This is one of those "rare" cases
where the aftermarket parts are actually better than what the factory
put on the truck. In idler arms, "bigger is better"
and the aftermarket idler arm shafts are a bigger diameter than the OEM
part, plain and simple. So if you have a factory arm and the plastic
bushings are shot, your two choices are to pick up a replacement
plastic bushing kit at the dealer or pick up one of the larger after
market idler arms (above).
4Crawler Offroad does not warranty bushings damaged by bent idler arms,
however, not to worry. If you bend an idler shaft and damage the flange
of one of the bearings, you can simply remove the bushings reverse them
placing the damaged flange bushing on top with flange loads are very
small. If you bend another, rotate the bushing 180 degrees. At this
point, if you bend another, you will need to purchase a new pair of
bushings and hopefully and idler arm brace too. The good news is that
hopefully your more expensive idler arm has been covered under warranty
by your local auto parts store.
Not required, the bronze bushings are self-lubricating. Grease will not
hurt them so there is no need to wipe clean grease off of the housing
and/or shaft but there is no need to install a zerk fitting if the
idler arm does not have one. Bronze is slightly porous and will absorb
oil from the grease and then slowly release that oil over time as the
shaft moves inside the bushings. If there is a grease zerk, by all
means you can use it to add grease as needed.
There are currently 3 options for RHD applications. The first is to
locally source an McQuay-Norris FA5040GL idler arm and then
install the bronze bushings in that and install that idler arm on your
vehicle. The second option is to make a hybrid idler arm, using your
existing RHD idler arm bracket (i.e. the part that bolts to the frame)
and a LHD McQuay-Norris FA5040 or the ProForged idler arm (using
just the internal shaft and arm portion that is identical between LHD
and RHD applications) then install the bronze bushings in your RHD
bracket and install the LHD shaft and arm into that. In order for that
to work, you need to check that the inner diameter (ID) of the bushing
holes in your bracket match the outer diameter (OD) of the bronze
bushings, that being 0.952" or 24.2mm. The third option is that we
have heard from a few RHD customers, that they were able to get a
suitable fit of the bronze bushings with their OEM idler arm, perhaps
with a little sanding or filing to get the bronze bushings to fit
inside the OEM idler arm housing.
If interested, we can supply the shaft and arm section of a ProForged
idler arm with the bronze bushings without the LED cast steel housing.
This combination cas ship for less than the full arm + mounting bracket
since it weights less. Simply order the Pro-Forged
arm/RHD option below...
We offer 3 options for your idler arm needs. If you have an existing,
compatible idler arm, you can order the bronze
bushings below. If you need a new idler arm and want to get one
that will work with the bronze bushings, you can order a new Pro-Forged idler arm below. And if you want
the new idler arm with a set of
custom-fit bronze bushings for later upgrade, you can order the full
For shipping times and methods, see below.
No Grease Fitting
This idler arm has the same 20mm shaft diameter as the genuine FA5040
arms. It does have a slightly undersized bushing seat in the main
casting, so you'll need to order the modified bushings above or you can
file/sand either the bushings or the bushing seat as needed. Cost on
the Pro-Forged idler arm is US$79.00:
This idler arm has the same 20mm shaft diameter as the genuine FA5040
arms. It does have a slightly undersized bushing seat in the main
casting and this kit includes the modified bushings. Available both as
separate arm+bushings or as an arm with the bushings pre-installed and
ready to go. Cost of the arm and separate bushings is US$114.00 and the
arm with bushings pre-installed is US$119.00. We only have a limited
supply and we need some time to schedule in the bushings installation,
so expect some delay in filling your order:
And for Right Hand Drive (RHD) applications, we are now offering the
idler arm+bushings less the heavy left hand drive frame bracket so that
you may retrofit the ProForged arm and bushings into your existing RHD
frame bracket. You may need to open up the bushing areas of the tube in
your RHD bracket slightly to fit the bronze bushings. This can be done
with a Dremel and sanding drum or a die grinder and round grinding
stone or sanding drum or even a hand drill. The benefit of the RHD arm
option is it saves over half on the international postage as it drops
the weight under the 4 lb. USPS flat rate envelope limit. Another
option is that we've had customers install a LHD idler arm on the right
side frame rail. You'll need to drill some new holes to line up with
the mirror image bolt pattern on the idler arm housing. If interested
in this, we can
send you a photo of a typical installation.
Be sure to supply an address that accepts US Post Office mail
deliveries and be
sure the address is valid.
[Last updated: 20.June.2019]