Rebuilding a Sherman combination transmission
Q: "How do I convert my 8N to a 12 volt system?"
A: You would need to get a Delco alternator (internal regular type is the
easiest), fabricate the brackets to mount it, get a wider pulley for the front of it, run new
wire to hook it up, and get a resistor to drop the voltage to the coil. If you're not familiar
with electrical systems, I would recommend buying the kit that is available for this. It would
be a little more expensive, but you get all the parts you need and instructions, too. Kits are
available from several sources. On the web, you can find them at
Just8Ns . If you're a determined
do-it-yourselfer, first pick up an alternator. Tell the parts counter guy it's for a '76 Chevy.
GM used this same alternator on about all it's vehicles from the early '70's through the mid
'80s. Fabricate some brackets to mount it. If you have the tools and ability to make brackets,
you won't need to ask how. If you have to buy the brackets pre-made, you are probably not
going to save any money and might as well buy the kit to start with.
Typical installation on a front distributor 8N
Typical installation on a side distributor 8N
The next step is wiring. Looking at the back of the alternator, you'll see a threaded post connector
sticking out. Along the top edge, just to the right of the post, you'll see two spade connectors
pointing up. These are numbered "1" and "2", left to right. It's best to have the correct double
connector pigtail to plug on to these spade connectors. You can snip one off at a salvage yard,
or pick up a brand new one at the auto parts store for a couple of bucks. They have them on
those red bubble pack cards with the HELP name. There will be a smaller black or brown wire on
the pigtail that goes to connector "1" and a larger red wire that goes to connector "2". The
larger red wire goes over to the left and connects to the rear post connector. Get a length of
heavy red wire (12 gauge minimum) and attach it to the rear post connector also. Run this wire
up to the junction block on the dash and connect it with the "hot" wire coming from the battery.
Get a length of smaller black wire (14 or 16 gauge) and connect it to the small
black or brown wire on the pigtail. Run it up to the dash. This is the exciter wire for the
regulator inside the alternator. This will connect to the side of the ignition switch that is
only "hot" when the switch is on, but it must connect through a resistor (side marker lamp) or a diode.
If you leave this out, you'll turn off the ignition switch and your tractor will keep running.
I have used diodes, and they work great for me. Side marker lamps sometimes work and
sometimes don't. Run up to Radio Shack and get a diode that's
reasonably heavy, at least one amp or more should do it. Wire it inline so that the arrow or ring painted around the end points to the alternator. There is one other option if you don't want to mess with a marker light or diode
and it's the one I prefer. Get a universal ignition switch at the auto parts store that has an ACC (accessory) position as well as an ON position. Hook the exciter wire to the ACC terminal instead of the ON terminal and you're in business. No
diodes or lights are necessary. Install the 12 volt battery, NEGATIVE
ground. Install a new 12 volt coil. These are available for front distributors, too. If you're
set on using the old 6 volt coil, you'll need a resistor installed inline to drop the voltage
to the coil. I have used a Delco Remy ignition resistor number D-1106 on many conversions and
it works great. If you have headlights, don't forget to replace the bulbs with 12 volt models.
Six volt headlights running on 12 volts burn really bright for a really short time. That should
be about it, you're ready go. Oh yeah, the fan belt seems too fat for the skinny little pulley
on the alternator. Most of the time it will work ok, the belt just rides a little high on the
pulley. If you've got an alternator/starter rebuilding shop in your area, they could fix you
up with a wider pulley if you need it. And, don't pitch out your old generator. There's a
market for those things.
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Q: "Why does my 8N run for a few minutes and then die?"
A: This is a very common complaint among Ford owners, and it usually stems
from one of two common problems. First is fuel. Dirt or crud in the fuel tank will clog up the
the shut off valve under the tank. The tractor runs until it uses up the fuel in the carburetor
and
then runs out of gas. After sitting a few minutes, the fuel will dribble down and refill the
carburetor bowl and the tractor will restart and run a few more minutes. Remove the fuel line
at the carburetor and open the shut off valve. You should have a good flow of fuel coming out of
the line. If you have only a slow dribble, or none at all, remove the shut off valve and bowl
assembly and give it a good cleaning with compressed air. Then unscrew the brass inlet elbow from
the carburetor and check the filter screen that is attached to the end of it. They get clogged
up, too.
If the fuel flow is good and the tractor still runs a while and dies, then you likely have the
other common problem - the coil windings are shorting out from the heat build-up and you lose
spark when the coil gets hot. When the coil cools off, you have spark again. You need a new coil.
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Q: "What kind of gear oil should I use in the transmission?"
A: Originally, the 8N used 90w (GL-1) gear oil for the transmission, rear
gears and hydraulics common sump. Capacity is 5 gallons. Many people today recommend using Ford 134 oil. This usually works fine in the 8N and is not so stiff in cold weather.
However, if your system tends to leak, or you have a lot of wear in the hydraulic system,
you probably need the heavier oil to keep things working and slow the leakdown rate. I
use 80w90 gear oil (GL-5) or 90w (GL-1) in mine, just because it always works fine for me.
When draining the gear oil, be sure to remove all 3 drain plugs (one under the transmission, one under the hydraulic pump, and a 3/4" pipe plug under the rear differential).
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Q: "How do I lube the steering gear box?"
A: The steering box uses 90 weight gear lube. Lots of people
have tired of leaking seals and now fill the box with thick heavy gear oil or grease.
If using grease I'd recommend a soft black Moly grease that will stay fluid and not
pack away from the moving parts or dry out. The biggest problem with the lube is the
upper thrust bearing which is above the full level in the box and seems to fail from
lack of lube. Over filling with a free flowing grease seems to solve this problem.
The early ('47-'48) 8N steering box had a 1/4" pipe plug on the upper right side of the
box. It could also be filled by removing the nut that holds the steering wheel on and
pouring the oil down the hollow steering shaft where it flowed out a cross drilled hole
and over the upper bearing.
The improved steering box (after 1949 serial number 216989) had a 1/8" pipe plug
on the upper left side of the box hidden under the dash suport bracket and was nearly
impossible to access.
The '50-'52 models could be filled through the upper right hand side bolt hole
where the dash panel attaches to the steering box.
After serial number 452913 a screw was added to the front side of the steering
column between the dash and steering wheel to allow adding lube from there. This
let the oil again flow over the upper thrust bearing on the way down (a good idea)
the same way the early models did.
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Q: "How do you replace rear axle seals?"
A: Rear axle seals leaking gear lube onto the rear brake shoes and onto the wheel
rim is very common on 8Ns, especially the early models before the added inner seal.
The major causes of seal leakage are improper (loose) axle bearing preload and worn
(loose) hubs on the axle shafts. Installing the correct number of shims to obtain
proper bearing preload when replacing seals is critical, as is having good
hubs. If your hubs were loose on the axles before, they will probably need replaced.
Once the hubs get worn, they will no longer tighten against the taper splines on
the axles and you'll never stop the leaks. I have personally never had to replace
an axle shaft - severe wear from loose hubs has always been in the hub itself and
the harder axle shaft was still good. You may not be so lucky. Inspect the hubs
and axle shafts closely for wear. If your hubs were tight on the axle and required
some force to remove them, they are most likely ok.
Replacing the seals is not too hard of a job if you're used to working on old
rusty mechanical things and have some basic tools. Here's a short rundown.
It's not meant to replace the I&T FO-4 shop manual for the 8N. You will need the manual
on hand before you ever start replacing the seals. Refer to it as you go.
A common sight, the oil soaked
rear brake drum on an 8N
If your tractor is a '48 or'49, you have just one
outer seal. If you have a '50 - '52 you have an outer and an inner
seal. You will need the (Ford part number) A8NN4248A
retainer assembly. This is actually the
outer seal. The seal is pressed into the retainer. You will need the
8N4284 gasket and the 8N4225
gasket. That's it, unless you have the '50
or later model in which case you will also need the 8N4233A
inner seal. First, remove the retainer
wires and loosen the hub center nuts about 1 turn. Rock the rear wheel from side to side.
If the hub doesn't move on the axle, drive the tractor around for a few minutes. Do some
figure 8's. Sometimes this will loosen the hub from the axle taper and save you from having
to use a large puller. If they still don't appear to be
loose on the axle, go ahead and remove the lug nuts and rear wheel. Remove the
brake drum (the 4 flat head screws holding the drum to the hub can be a bear to remove
if they're rusted in - and they usually are). Remove the brake shoes. Pull the hub off,
if it's loose. If it's not, get a large 3 jaw puller and start tightening. Make sure to
leave the hub retaining nut on the axle but have it a couple of turns away from the hub.
Without the nut, the hub can pop off suddenly and do some serious damage to your knee caps.
Put pressure on the puller and tap the hub. Some are really on there and I've even had to
resort to heat from a torch to get them to pop loose. Once it's off, remove the 6 bolts
holding the retainer and seal assembly and pull it off. The brake shoe pivot plate will
come off now. Remove the last 2 bolts from behind (tractor side) and pull the bearing
retainer and backing plate and slide the axle out to get access to the inner seal
('50-'52). Remove and replace the inner seal.
The inner seal on the '50 - '52 models
On early models, removing the backing plate and axle
is somewhat unnecessary, but you should go this far anyway to reseal the area where
grease can leak between the backing plate and axle housing flange and also make sure you
have the right amount of shims to properly load the axle bearings.
Disassembled and ready to clean
This is the time to inspect the axle bearing and cup for wear and to reset
the axle bearing load. Make sure the bearing looks good, no pits in the cup or on
the rollers. Make sure the backing plate, bearing retainer, and all shims
and/or gaskets are clean. I select the shims needed to load the axle bearings to zero load.
Zero is hard to describe. It's no bearing load and no end play. If you're not sure how
many shims to use, follow the procedure in the shop manual to set the load. I think their
procedure loads the bearings too tight, but it's worked ok for a lot of years, so who am
I to question it. Zero load is desired, but if you're in doubt, a little too loose is better
than too tight. Too tight will ruin the bearings. Be sure to pack the axle bearing with grease before you
reassemble if you have the later model with inner seal. Clean all parts in a good solvent.
Cleaned up and ready to assemble
Reassemble with some Permatex Ultra Blue silicone RTV on all flange faces and wherever grease
could leak out. The Permatex No.2 non-hardening form-a-gasket works fine, too. Use sparingly.
Too much sealer just oozes out all over and is wasted as well as being ugly and possibly
screwing up the bearing load you just worked so hard to set.
Use sealer on all flange faces
The 8N4284 cork gasket goes over the axle
between the axle bearing and the hub. The 8N4225 cork gasket goes between the brake shoe pivot
plate and the retainer/seal assembly. Use Ultra Blue there, too.
Putting it back together with the proper load
 |
 |
|
8N 4284 axle to hub cork seal installed |
Sealer on every shim and face |
I put a small bead of sealer
around the axle shaft splines before sliding the hub back on to help keep the gear lube
from leaking out the front side behind the nut. Wipe a little oil or grease on the inside
lip of the new seal and around the seal diameter on the hub before the hub goes on. This
keeps the seal from running dry on the hub and getting hot right away.
Installing the hub
Put the hub on
and tighten the nut to hold it. Put the new, dry brake shoes on, install the drum, put the
rear tire back on and finish by tightening the hub retaining nut REAL tight and replacing the
wire clip. Adjust the brakes, and you should be leak free and stopping on a dime for the next
several years.
Finished and ready for the brake drum and wheel
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Q: "Why is water leaking out of my rear tires?"
A: This isn't actually water unless you live in a very warm climate.
It's most likely a calcium chloride mixture that's heavy and won't
freeze. It's also extremely corrosive and will destroy your rims if
it's leaking inside the tire. Tires are filled to add weight for extra
traction and as ballast for a loader. You can drain it out yourself,
but getting it back in the tire is best left to a tire shop that has
the necessary equipment to pump it in. When adding air to a filled
tire or checking
the pressure, always have the valve stem at the top (12 o'clock
position). To see if your tires are filled, position the valve stem near
the bottom and carefully let a little air out of the valve stem. If
the tires are filled, you will see liquid come out. To find out how
much liquid is in the tire, hold a screwdriver by the blade, put your
ear to the top side of the tire, and use the screwdriver handle to
lightly thump the side of the tire starting at the bottom and working
you way up gradually. You will hear a distinct difference in the sound
from the tire when you reach the top of the fluid level and move into
the air space. With a little practice, you will be able to pinpoint
the exact level of fluid in the tire. Tires should never be filled more
than 2/3 full. More than that can cause instability on hillsides, etc.
When removing a filled tire from the tractor be very
careful. They're very heavy and when tipped can fall over and injure
the person trying to handle it. Have a strong helper around when you
take these off.
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Q: "I changed my oil and now I have no oil pressure."
A: This can also happen when a tractor has been sitting for a long
period of time without being started. It usually happens because the
oil pump pickup tube has come loose or the gasket on the oil pump is
bad and the pump is "sucking air" rather than pulling oil up from
the sump. Badly worn gears in the oil pump can cause it, too. It's a
sign that something in the oil pump area needs attention soon. The
easiest way I've found to prime the pump and get it going again is to
remove the oil pressure relief valve from the front of the engine. It
is a 15/16" nut on the top front of the timing cover just below the
water pump.
Relief valve location
Remove the nut and pull out the spring and valve poppet.
Get a trigger type squirt oil can and put the nozzle in the hole that
the valve poppet goes into. Squirt several shots of motor oil into the
hole. This oil will run down into the top side of the oil pump and
collect on the pump gears. This is usually enough to prime the pump.
Replace the poppet and spring and nut and fire it up. You should get
oil pressure back again. If not, or if your oil pressure suddenly dropped
to zero while the engine was running, remove the oil drain plug and
verify that the pump pickup tube is still intact. It could have broken
off at the pump which is above the oil level in the pan.
Q: "How much oil pressure should I have?"
A: The relief valve spring is designed to hold the
poppet on the seat until oil pressure is 35-40 psi (Yes, the poppet IS
supposed to have that flat spot on it). The relief valve only sets the
maximum pressure attainable and has no effect on raising a lower pressure
unless the spring is weak or broken. If your engine is in good shape,
you will see 35-40 psi, hot or cold, at anything over an idle. Pressure
at idle will be about 25. The main cause of low oil pressure is worn
crankshaft bearings (main and rod bearings) followed by worn gears in the
oil pump. The first symptoms of wear are good oil pressure when cold
that drops off when the engine is hot. This is a sign that the clearances
have opened up in there and the oil that has thinned when hot can now
rush through the bearings faster than the pump can pump it. The oil
pressure on your gauge is back pressure, or the resistance against the
oil escaping from the clearances. No back pressure = no oil pressure.
The oil pump relies on a close runnng fit between two gears to move the
oil along into the engine. If these gears are worn excessively you won't
build pressure either. Low oil pressure is not a death sentence for an
8N, they will keep going a long time if you have at least 5-7 psi at low
idle when hot and 15-20 psi when hot at fast idle. Less than that means
your engine needs rebuilt soon. If it was recently rebuilt, someone skipped
something important or did something wrong. Be sure to verify that your
oil pressure gauge is reading accurately before you condemn the engine.
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Q: "I'm rebuilding the engine. Should I get 3
ring or 4 ring pistons?"
A: Go with the 3 ring pistons. The 4 ring pistons which are touted to
seal better actually have more drag (friction) which causes more heat
and faster wear that would offset any gains from the extra ring.
Q: "Which type sleeves do I have?"
A: If your engine is serial number 8N433578 or later, you have the
.090" wall thickness cast iron sleeves. All earlier engines could
have either sleeve since many were rebored at overhaul time. The only
way to know for sure is to disassemble the engine and take a look.
I've heard that some suppliers of sleeve kits only sell the heavy
wall sleeve and tell you that the older block must be rebored for
the newer sleeve. This is not true. The .040" wall thickness sleeves
are available and will still work fine in the older engines.
Q: "How do I replace the sleeves?"
A: There are numerous methods for removing and replacing the sleeves.
Obviously, the easiest and safest way is to use a commercial sleeve puller
set. Reverse the puller setup to install the new sleeves. Most machine
shops that do engine rebuilds will have one, and it's usually a pretty
reasonable price for them to do the sleeve R&R for you. You may be able to
rent one, or you could make your own that will do the job. The .040" thin
wall steel sleeves (commonly referred to as tin can sleeves) can be
removed by using a tool to crush the sleeve inward away from the cylinder
wall. This is a risky proposition however, as many cylinder walls have
been damaged and even broken by people trying to wedge a screwdriver or
other tool between the sleeve and cylinder. Another method that seems to
work well on both types of sleeve is to run a bead of weld from top to
bottom of the sleeve (not too hot!). As the weld cools it contracts the
sleeve and you can usually slide them out by hand. Clean the bores of
carbon and scratches but do not remove any stock or you could find your new
sleeves are loose. Freezing the new sleeves (VERY cold) will contract the
diameter and allow the sleeve to drop right in the bore. However, I've never
had a lot of luck with freezing at home since the sleeves warm up by the
time I get them from the freezer to the engine block. Usually, the sleeve
will press in the bore by pushing it down by hand. Place a short length
of 2x4 across the top of the sleeve and lean on it. Make sure the sleeves
are starting into the bore straight! You can tap on the 2x4
lightly with a soft mallot but never hammer on the sleeve itself. If your
sleeves are tight in the bores and won't push in, make a puller to pull them
in. Get a piece of heavy flat stock that will span the top of the sleeve and
another that will span the bottom of the engine block. Drill a 5/8" hole in
the center of both pieces of stock. Use a length of 5/8" threaded rod and
2 nuts between the 2 pieces of stock to pull the sleeves in. The top of the
sleeves should be flush with the top deck of the block when installed. The
sleeves were intended to be a light press fit into the bores. If you find
that one of your new sleeves is loose in the bore, try another sleeve.
Don't assemble the engine with loose sleeves, call a machine shop and see
what other options they can offer.
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Q: "Do I have to use non-detergent engine oil in my 8N?"
A: No. Todays motor oils are far superior to what the manufacturers
suggested 50 years ago. Use any good straight weight or multi-vis motor oil in your 8N and
it will be just fine. Crankcase capacity is six quarts with filter.
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Q: "Do I need to add a lead substitute to my gas?"
A: No. Lead substitutes are nothing but octane boosters, and with the 6.5
to 1 compression on the 8N, you certainly don't need high octane. The 8N valve seats are
hardened inserts and will not be harmed by unleaded fuel at all.
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Q: "Where can I find a wiring diagram for my 8N?"
A: Here's one -
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Q: "My hydraulic lift isn't working right."
A. The 8N hydraulic system is simple yet elegant and works great when
properly adjusted and maintained. It consists of a pto driven piston type
pump with internal control valves and a lift cylinder connected to the
rear lift arms. The control lever and quadrant moves the valve spools on
the pump to control the lift. The most common complaints are addressed
below. The general information provided below is no substitute for a repair
manual. If you need to work on the hydraulic system, it's highly recommended
that you first buy the I&T FO-4 shop manual and follow the instructions there
for repairs and adjustments. It's also highly recommended that you change
the hydraulic oil (gear oil) and keep it fresh and clean at all times. The
oil sump holds 5 gallons that is shared with the transmission and rear end
of the tractor. It has a tendency to accumulate moisture from condensation
inside the gear cases and the water collects in the bottom of the sump where
it is drawn directly into the hydraulic pump. In cold climates the water can
freeze and break the chambers in the pump. You definitely don't want that to
happen. If the oil looks milky, it's got water in it. Change it.
Q. "My lift isn't working at all."
A. If the lift won't raise at all, first make sure the pto is engaged and the
pto shaft is turning as it should be. Make sure the oil level isn't low.
If those two things check out ok turn off the engine and remove the right
side access cover (the one with the dipstick) and slide your hand down
along the control rod into the oil and feel the end of the rod where it
goes into the control valve pivot. Make sure the rod is connected and
that it is moving the control valve spools in and out as you move the
lift control lever up and down. Other possibilities are a defective relief
valve or a ruptured oil tube that goes from the pump base to the top cover.
To check these, leave the side cover off and start the tractor. Have a fairly
heavy weight or load on the lift arms. Raise the lift control lever and watch
inside the cavity for oil spraying out in the area of the relief valve or from
the side of the cavity where the tube is located. If no oil is spraying out
anywhere, you could have a bad pump. Check the pump pressure as outlined in the
I&T FO-4 manual.
Q. "My lift only comes up half way then stops."
A. This is a very common complaint and can almost always be attributed to a worn
cam follower pin in the lift control linkage. Loosen the 4 bolts holding the
quadrant control lever bracket to the top cover. Slide the quadrant bracket
toward the rear of the tractor (bolt holes are elongated). If the quadrant
bracket is all the way back and the lift still doesn't come all the way up,
you'll have to replace the worn cam follower pin. Remove the top cover and
place it bottom side up on the workbench.
 |
 |
|
Cam follower pin location |
A badly worn pin |
Find the worn pin. Disassemble the
control linkage until you can get the part with the worn pin out of there.
Press or drive the worn pin out. Replace with the correct hardened dowel pin
part number 374072S from Ford/New Holland. This is listed as a 5/16" x 7/8"
dowel pin but it is actually .309" diameter not 5/16" (.3125"). Pressing or
driving a common .3125" pin into the .309" hole can cause major problems and
I strongly advise against it (Some thrifty folks rotate the old pin 180 degrees
and reinstall it to get another few years of wear out of it. That usually works
ok if you can't spare the two bucks for a new one). Reassemble the linkage
and adjust as per the shop manual instructions. Many times you will find that
simply replacing the worn pin will take care of the problem without any further
adjustments, but you have to completely reassemble the tractor to find out if
you are lucky or not. Before replacing the top cover, take the time to inspect
everything else in there for wear or other problems. This is an excellent time
to rebuild the lift cylinder also. See the next question.
Q. "My lift drifts down when the pto stops."
A. Leakdown is probably the most common complaint with the N tractors, but it's usually
easy to fix. If you have an implement on the lift and it drifts down over a few minutes time after the tractor is shut off you have some leakage. If the implement drops as soon as you
push the clutch pedal in, you have major leakage.
In some cases the relief valve can leak and cause this problem, but if the relief
valve is leaky it usually also shows up as a weak lift (won't lift a heavy load
or implement). The control valve spools in the pump base can leak due to scoring
in the bores but this is rare and generally not repairable except by a major pump
rebuild. The most common cause
of leakdown is worn lift cylinder piston rings. You can determine if the leakage is
coming from the lift cylinder by removing the right side cover (the one with the
dipstick) and starting the tractor. Have a fairly heavy weight or load on the lift arms.
Raise the lift control lever and watch inside the cavity for oil leaking out from above
in the area of the lift cylinder. If the cylinder is leaking, you will see it. If the
relief valve is leaking you will see the oil bubbling up from the pump area. The N tractors originally had a piston with 3 cast iron rings to seal it. These rings are still available, inexpensive and will work just fine, but a small amount of leakdown is normal and is to be expected with them. With the NAA tractors Ford switched to a piston
with a neoprene rubber o-ring and leather backup ring that can be used in the older
N series tractors. This provides a much more positive seal to eliminate the small leakage
from the cast iron rings. The NAA piston and seal will cost more to replace than just
buying new cast iron rings. The determining factor in which way to go is the condition of
the cylinder bore. Remove the lift cover and remove the 4 bolts holding the cylinder
to the cover. You can remove the piston fron the cylinder by applying a little
compressed air to the oil inlet hole in the cylinder. Don't use a high pressure or
you'll blast the piston out of there like a rocket. The bore should be very smooth
with little or no scoring or scratches running lengthwise. It can (and probably should)
be lightly honed to a cleanup. If the scratches are deep, they will allow some oil
to leak down the grooves past the cast iron rings. In this case the NAA seal will
work better, but only for a short time. The scratches or grooves will chew into the
new neoprene seal and it will leak worse than ever. If you have deep scratches and
do not want to spend the money to replace the entire cylinder assembly you should use the
cast iron rings and live with the small leakage. If the cylinder bore is in good shape
or has only very faint scratches or grooves use the NAA piston and seal.
Q. "My lift went up but now it won't go down."
A. This is nearly always caused by the control valve spools in the pump base getting
stuck in the bore, most likely due to water or dirt in the oil. Turn off the engine
and remove the right side access cover (the one with the dipstick) and slide your
hand down along the control rod into the oil and feel the end of the rod where it
goes into the control valve pivot. Make sure the rod is connected and that it is
moving the control valve spools in and out as you move the lift control lever up
and down. Chances are, you will find that the valve pivot is stuck and not moving.
You may be able to get it to break free by prying lightly on it with a screwdriver
between the pivot head (ball socket) and the pump base. When it breaks free and starts
working again, CHANGE THE OIL. If it's really stuck tight, you'll have to pull the
pump and rebuild it.
Q. "My lift works by itself but not with a heavy load on it."
A. This could be severe leakage at the cylinder, a bad relief valve, or a badly
worn pump. Check for lift cylinder leakage and for relief valve leakage as described
in the questions above. If no major leakage is noted, then check the pump pressure
as outlined in the FO-4 manual. A rebuild is probably in order.
Q. "My hydraulic pump makes knocking noises under load."
A. What you're hearing is the sound of worn cams/pistons in the pump. When the pump is
new it runs quietly, but as the cams wear they begin to knock as they actuate the
pistons from side to side in the pump. The louder the knock, the more wear your pump
has on it. It's generally not an immediate pressing problem. If the knock is faint you
can probably put off repairs for quite a while. If it's knocking loudly you should buy
a pump repair kit and do a rebuild before it quits all together.
Q. "My lift is very jerky and erratic when raising."
A. This is usually a sign of a defective or sticking valve in the pump. The pump piston
pushes the oil out then pulls it back in as it returns. Time for a pump rebuild.
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