Diff Breather Hoses
I would like to install longer diff breather hoses. Is this
hard to do?
What is the max fording depth with stock diff breather
The safest depth I believe is about 12 inches of water.
The standard breathers have a flap and a spring in them and
they can block open. This means that water will enter the diffs
and the water in extreme pressure diff oil breaks down the ability
of the oil to take the load and the gears actually wear out. (ed
- The flap can also snap shut when the diff housing is cooled in
water resulting in axle seals popping in and sucking water).
I extended the breathers using normal fuel hose and from the
back I ran the hose up to the floor and then along the chassis by
zip tying it to other lines (ed - avoid running them along
brake lines as they can get caught on branches etc) then up to
the top of the engine bay. The front was done likewise. You need
about 8 metres of hose (I think, I cant remember exactly). (ed
- Don't forget to allow for suspension travel in length of hose at
I used T fittings into the rear line to also take a breather
from the gearbox/transfer. The breather on the gearbox ends at the
top of the bell housing at the rear of the engine. Its had to find
but you can run your hand along the top and feel it. I unclipped
the end from the last fitting on the box and pushed on the new
line and joined it into the rear line. Where ever I added the line
to I then zip tied the hose to the fitting, although hose clamps
could be used.
The T fittings are available from irrigation or auto parts
I then installed a small petrol fuel filter in the end of the
line in the engine bay with a short length of hose 8 - 10 inches
hanging down. The filter is to stop dust entering and the hose
hanging down is to provide a u shape to stop water entering if you
get it really wet.
Its also worth while changing the diff oil if you even think
they might have a bit of water in them as it works quickly to ruin
If you have an under bonnet compressor, like an ARB one, it is
also worth while to provide it with a breather hose as they fill
with water/mud through the little bronze filter and they have to
be stripped down and the bearings replaced.
The cost all up including a small pack of zip ties and T
fittings was under $50 plus a hour or so under the car.
> these 'valves' can block up and cause more problems.
Best to toss them and
> use some other filtering arrangement, 'u' tube, petrol
These flapper valves are designed to let air out of the housing
as it heats up. They snap shut and create a lower pressure in the
axle housing when it's cold. Nasty when the axle housing is
quenched suddenly when you enter cold water. When installing the
extension diff breathers on my latest 80, there was an audible
rush of air when I pulled the diff breather hose off the barbed
fitting on the housing.
A cheap fuel filter or the filters ARB use on their air
compressors are good to use on your extension diff breathers.
Especially if you're running air lockers. These will let enough
air through in the event that you have a locker piston seal
failure and end up pumping 120 psi through your axle housing.
just finished installing longer breather hoses on the front and
rear diffs yesterday (will install one on the transfer case later
this week, ran out of time;-).
after sizing up the situation, i purchased 25' of .250"
i.d. fuel line hose, two (2) tee fittings, six (6) hose clamps, a
bunch of 10" tie wraps, and went to work.
disconnecting the existing hoses was easy enough, and the front
hose yielded a very good filter/baffle to use for the new system.
on '97's, the front breather connects to a roto-molded plastic
container with a pop filter on the top of it. also, the metal
bracket that holds this part to the frame can be used when you
reposition the filter under the hood. I do not know if earlier 80
series have this, if not, Dimitry used an in line fuel filter on
i installed the front diff hose first, which took approx. 1
meter of fuel line to run, allowing enough free play for
suspension articulation. two (2) tie wraps held it in place. i
ended up running the hose up into the engine compartment,
terminating next to the fuse box. the bracket that originally held
the plastic filter to the frame, was reshaped and used to attach
the filter in its new position (i will take photos of all of this
later, and post, as trying to describe exact locations is
difficult, at best;-). both ends of the new hose were secured with
the rear diff was even easier to work on, and after allowing
enough free play for articulation, and using a hose clamp on the
diff breather fitting, it is a straight shot up the frame on the
drivers side, using tie wraps to secure the hose in place. i used
approx. 4 meters of hose for the rear diff.
i used one of the tee fittings to patch the rear diff hose into
the front diff hose, just as the front hose crosses the frame and
starts to head into the engine compartment (again, photos will
after testing the hoses today (long on-road, and some off-road
driving), i am happy to report all are doing well.
as i mentioned, i will attempt the transfer case breather hose
this week, as i ran out of time this weekend, and i really would
like to get the cruiser up on a lift, to be able to really see up
into the transfer case area. i looked at a shop manual, and saw
what i believe to be the breather fitting, located way up on top
of the case (this makes sense), and this area only has little more
than a hands thickness of clear space to work in.
i hope that this account prompts any other on the list that
have been contemplating doing a diff breather mod, to go ahead and
do it. the way i rationalized it is as follows:
1. the materials cost less than $40.00 to obtain (you can use
less expensive fuel line hose, i suppose, and this would lower
2. the whole job took me less than 3 hours total (this with
LOTS of rerouting hose, to obtain maximum safe routing). i am sure
it can be done in less time than this.
3. the cost of rebuilding a diff that has sucked water is
considerably more than the material cost, and my labour for three
hours (even though i do charge a lot for my consulting time;-).
Instructions: How to Install Gearbox & Differential Breathers
The Test Vehicle
The test vehicle was 1994 manufacture (Australian version) with the following
The success of these modifications on your vehicle will depend upon any
variations from the configuration used to provided these instructions,
components used, and your mechanical engineering ability. Given those variables,
I can not provide any guarrantee as to the level of success of failure
you may achieve.
manual 5 speed transmission
mechanical centre diff (same transfer case housing as viscous coupled)
no diff locks
ARB side steps (mounting hardware seen in picture)
There has been a lot of talk about the effectiveness of the differential and gearbox breathers used on the 80 series Toyota
Land Cruiser. I started
to look in detail when oil was noticed coming out of the front differential
The front diff breather enters the axle housing about 25mm above the
axle centreline. The rear breather is connected to the top of the rear
axle housing. It is interesting to note that the 60 series Land Cruiser
had the breather entry at the top of both axle housings.
When the axle housing breather hoses were removed there was a noticeable induction of air into the axle housing, which had been under vacuum.
A number of small modifications have been made to (hopefully) resolve
the discharge of front diff breather, and prevent the breather or seals
from sucking in water or dirt during river/creek/mud hole crossing.
The only options, not detailed here, are to;
These are sub projects that others may consider investigating, and writing
the appropriate methodologies.
use a 60 series breather valve instead of modifying an existing valve
incorporate the main gearbox,
use a garden variety fuel filter on the combined breather line,
pressurise the combined breather line to a low pressure (1-2psi ??)
The modifications are simple, and can be carried out with normal hand tools
These modifications include;
modify the breather valve
relocate the breather valves higher
connect all breather lines
possibility of pressurising the diff & transfer case
The Breather Valve
The breather valves are designed to permit gas (and liquid) exit the axle
or transfer case housings. A modification needs to be carried out on only
Below is a cross section of the original breather valve. The valve
body is brass, with a steel cap, spring, and rubber flapper.
The 60 series Land Cruiser used a plastic body and cap, without
either the spring or rubber flapper. You may wish to purchase one of these
if you do not wish to modify one of the original breather valves.
The 80 series breather valve after modification is shown below;
Tools required to carry out the task are listed below. Most of these tools
are probably already in your tool kit.
12mm combination spanner
14mm socket (from memory)
ratchet and extension
flat blade screw driver
pointy nose pliers
ramps, or jack and jack stands
The following parts are required to complete the modification. Most are
available from auto parts or brake repair shops.
7 metres of 1/4" hose (rubber fuel line)
10 "P" clamps to suit above hose (with 10mm mounting holes)
10 hose clamps to suit rubber fuel line above
3 1/4" brass "T" pieces (the ones with barbs)
1 3/8" rubber blanking cap
8 7" long cable ties (BLACK only)
8mm bolt - optional
The procedure is simple, and will take about 2.5 hours once you have all
the tools and parts required. No attempt has been made to connect into
the main grearbox breather, as the gearbox needs to be lowered to get access
to this breather (unless you have minute hands, and double joined arms/hands).
Then new breather line will run from the rear axle housing, to the inner
rear cross member, along the inside of the left chassis rail to the transfercase
cross member. From there it will split to run up the side of the transfer
case to the transfer case breather outlet, and forward along the chassis
rail to front axle house breather valve hose mounting point on the chassis.
At this point the new breather line will split to connect to, the front
axle housing breather outlet, and the other remaining leg will run up into
the engine bay.
The new breather line will be secured to the chassis with P clamps,
and cable ties were access to the bolt onto the chassis is extremely difficult (like behind the fuel tank).
Brass "T" pieces are used at the transfer case cross member, and just
forward of the left engine mount. Hose clamps are used at each breather
outlet and each "T" piece.
Work is commenced from the rear axle housing towards the from of the
car. Breather lines are always mounted above the brake lines.
Please read ALL of the modification details before commencing.
There are a lot of steps involved, but most are just reasonable engineering
This procedure has worked fine for me, on 1FZ-FE engined '94 model.
Your mileage may vary, so use these instructions as a guide.
Clean the underside of the car with degreaser and a pressure was, then
find a level, and preferably clean dry hard surface. Get the car on the
ramps or jack stands. Proceed as follows;
cap one end of the new breather line
feed the breather line (capped end first) rearwards from the transfercase
crossmember along the inside of the chassis rails, above the brake lines)
past the main fuel tank
slip one P clamp (tail pointing rearwards on the right side) over the
new breather line
slip one hose clamp over the new breather line
remove the original rear axle housing breather hose (completely)
remove the cap in the new breather line
push the new breather line onto the rear axle housing breather outlet,
and secure with the hose clamp
ensure that there is sufficient hose to allow full articulation of the
suspension without fouling or rubbing
secure the new breather line to the fuel tank cross member using the existing
parking brake cable guide bolt
remove the bolt holding the brake lines to the chassis at the rear of the
install a P clamp over the new breather line, tail outer most and pointing
loom the new breather line neatly across the rear of the fuel tank, and
secure with cable ties
secure the P clamp and brake lines with the original bolt
remove the bolt holding the brake lines to the chassis at the front of
the fuel tank (and behind the transfercase crossmember)
pull any excess new breather line forward from in front of the fuel tank
install two P clamps over the new breather line, tail outer most and pointing
down, just forward of the fuel tank
secure the new breather line to the brake lines behind the fuel tank with
cable ties at each brake line clip
secure the rear most P clamp and brake lines with the original bolt
Here you have two options, one is to leave the original forward breather
in place, the second is to remove it completely
NB: small hands are an advantage
here, and its a fraction easier if you work from the left side of the car
A Follow this process if removing the forward breather hose
- Remove the forward breather hose at the base of the main gearbox gear
lever and plug with 8mm bolt.
- Cap the port that the hose came off with the 3/8" blanking cap
- nstall brass T piece into the breather line between the main gearbox
and transfer case. Secure with hose clamps
B Follow this process if leaving the forward breather in situ
- Remove the main gearbox breather just forward of the T piece.
- Insert the 8mm bolt into the end of the hose and secure with the hose
- Tie the hose to the top of the main gearbox to avoid it snagging while
on the trail.
slip one P clamp (tail down and forward most), and one hose clamp over
the unused end of the new breather line
secure the new breather line to the T piece on top of the gearbox
using the hose clamp
route the new breather line down the left side of the transfer case
remove the second lowest transfer case housing bolt
secure the new transfer case breather line with the P clamp against the
transfer case using the bolt just removed
loom the new transfer case breather line along the transfer case cross
member, and up to the top of the chassis rail
cut the new transfer case breather line at the top of the chassis rail
cut the rear axle housing breather line just forward of the transfer case
slip one hose clamp over each of the new rear axle housing breather and
new transfer case breather lines
trim each new breather line to permit a tidy fit of one brass T piece
secure the new breather lines to the brass T piece with the hose clamps,
with the new transfer case breather line connecting to the terminating
portion of the brass T piece
slip one hose clamp over a the remaining section of new breather line
secure the remaining section of new breather line to the remaining unused
portion of the brass T piece
secure the rear axle housing breather line to the chassis using the mounted
P clamp and bolt from the original rear axle housing breather support
slip all but one of the remaining P clamps over the new breather line
route the new breather line forward from the T piece, under the engine
mount, to the front axle housing breather support
secure the new breather line to the chassis using bolts from the brake
line mounts and P clamps
use cable ties were appropriate
cut the new breather line approximately 15cm forward of the left front
remove the front axle breather hose from the front axle, and chassis rail.
Listen for the suction!
slip a hose clamp over the unused section of new breather line
install this section of new breather line onto the front axle breather
outlet, and secure with the hose clamp
allow sufficient breather line for full front axle articulation from the
front axle housing to meet up with the breather line from the rear axle
and transfer case.
cut the new front axle housing breather line at this point
slip one hose clamp over each of the the new front axle housing breather
line, and rear axle/transfer case breather line
clamp the rear axle/transfer case breather line to the terminated part of
the remaining brass T piece with the hose clamp
clamp the new front axle housing breather line to the brass T piece using
the hose clamp
route the remaining section of new breather hose down along the left inner guard
in just in front of the left engine mount
slide one P clamp and one hose clamp over this section of breather line
secure the breather line to the remaining outlet of the brass T piece using
the hose clamp
secure the P clamp using the original front axle breather hose support
bolt and chassis mounting hole
route the section of breather hose to a convenient location in the engine
bay which has an 8mm bolt hole. This will depend on the extra equipment
installed on your car
rework either the front or rear breather hose support bracket to hold the
new breather line
mount the breather line support bracket
install the breather line into the support and secure by compressing the
metal loop slightly
cut the breather line, leaving sufficient to install an original breather
slip a hose clamp over the end of the new breather line
non destructively remove one of the original breather valve caps
re-assemble the breather valve without either the rubber flapper or spring,
as per the modified 80 series breather valve drawing
remove the breather valve from the original breather hose
install the modified breather valve into the open end of the new breather
line in the engine bay
secure the modified breather valve onto the new breather line using the
ensure all clamps are tight
inspect brake lines for any damage
account for all unused clamps and hose
account for all tools used
clean the tools
clean thy self
remove the car from the ramps or jack stands
Pictures of the Installation
Below are pictures which show various parts of the completed installation.
The following photo shows a view forward from the transfer case cross
member to the front brass T piece, were the breather line splits to go
down to the front diff, and up into the engine bay. The hydraulic line
seen in the picture is the clutch line. The white object on the right is
the engine sump.
The second photo shows details of the area around the transfer case
T piece. You will notice the P clamps using the same bolts as the new breather
line, and the support U bolt for the ARB side steps (left of the picture)
routed under the brake lines and new breather lines. Fuel lines can be
seen on their way to/from the engine in the centre of the photo.
If you have a full time 4WD (as most are) you can possibly trace the
breather hose from the 4WD servo motor as below;
or from the actual transfer case (all versions) to the T piece on top of
the transfer case itself, as below.
The main gearbox breather connects at the base of the shifter tower.
A hose connects to the transfer case from the rear, and then runs forward
to a flapper valve at a point behind the motor. You need small
hands to access these from under the car.