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The parts book for the A/B tractors illustrates the control parts. Here is a write-up I did for someone else a while back: The system works fairly well when it is maintained, but it does require some
regular maintenance. Engine exhaust is both hot and full of corrosive
combustion byproducts, thus the need for ongoing care. The pressure valve (on top of the manifold) tends to have problems from rust
and scale. The valve plate can be cleaned up with a file. The surface it
mates to in the lower half of the housing is a little more difficult to
clean up because it is recessed into the housing. Keeping rain out of the
exhaust reduces the problems with this valve. There is a drain hole in the
lower half that should be kept open, to reduce the chance of water
collecting in the valve. By the way, the manifolds have a drain hole as
well. These are usually filled with rust. But when new and a Lift-all was
installed, there was a small plug to install in the manifold drain. There is a piece of pipe that connects from the pressure valve to the
control valve. Originally, this was one piece of pipe with 2 bends in it.
There were no elbows, unions etc. that often are found on the tractors now.
When the parts were new and the threads all free, it was possible to install
these parts with the manifold in place. The control valve can also have
problems from corrosion. Moisture likes to collect in it. The main
maintenance items inside this valve are a metal disc and a neoprene seat.
With time, the seat tends to swell up rather than dry and harden. There are
2 problems typically caused by this valve. One is that the system won't go
down, the other is that it won't stay up. Either of these problems usually
comes back to the disc and seat. When you work on this valve, clean it up
and make sure that the entire inside has a coating of grease. Looking at
the back side of this valve you will see 2 or 3 grease fittings (or at least
things that look like fittings). 2 are grease fittings. If you see three,
the middle one is really where a hose that is no longer present had been
connected (more about that hose later). There is a difference of opinion as
to whether those fittings should be greased. My opinion is to grease them
but only very lightly, one squirt from the grease gun to do BOTH fittings.
Heat is the major enemy of this valve. It is important to never leave the
system with the large hose connection open. A continuous flow of exhaust
through the valve will overheat it. So always keep the outlet capped or
connected to a good lift cylinder. >From the control valve is a hose (garden hose size) that connects to the
lift cylinder. Although a garden hose washer will fit the end of this hose,
it won't work long before it swells up. The proper washer is neoprene. The lift cylinder is 7 inches in diameter and uses a leather seal on the
piston. The tube of the early cylinders was made of brass. Later on, they
went to steel with a porcelain coating. I am sure that was a cost reduction
change. Plain steel would have probably never held up in that use. These
usually hold up pretty well. Failure is evident when exhaust can be seen
coming out the vent at the top end of the cylinder. Again, much flow here
will result in the exhaust overheating the control valve, hose etc. The
lift package itself is an attachment of the tractor and includes this
cylinder. However, the mounting brackets depend on what implement it is
being used with. The ubiquitous bracket to the left of the radiator is for
the cultivator. Plows mounted the cylinder to the side of the bell housing
in a nearly horizontal position. Other equipment had other mounting
arrangements. The control handle came in 2 different styles. The earlier version was a
straight rod with a ball on the end and some lugs welded to the sides of the
rod for holding it in different positions. The guide for this handle was
attached to the steering shaft support. On the support was a small pressure
diaphragm unit with a latch. The latch would hold the control rod in the
rearmost, lift position. A small rubber tube ran from the control valve
back to the diaphragm unit. When pressure hit a certain level, the latch
would release the rod allowing it to move forward to the neutral position.
The diaphragm unit had an adjustment to set the pressure required for the
release. The forward end of the small tube connected to the control valve
between the 2 grease fittings. The forward end of the control rod connected
to a rock shaft below the fuel tank and the rock shaft was linked to the
lift valve. The link between the rock shaft and lift valve included a
spring assembly so that the valve would be held shut when the control rod
was latched back. When the control rod was pushed fully forward, linkage to
the control valve released it so the pressure stored in the lift cylinder
was released through the exhaust system. The pressure driven latch on the
control rod must have worked when they were new, but I have never seen one
that did. The later style control handle eliminated the troublesome diaphragm unit and
release mechanism. The control rod was replaced with one that came to the
rear with 2 parallel rods. A handle stood vertically between them and
continued upward to a ball on its end. The upper rod had a spring assembly
that allowed it to stretch slightly when the handle was pulled back. A
redesigned guide allowed the upper rod to be latched in the rear position.
The handle had to be manually released when the cylinder was extended.
Since this design had a spring built into the handle, the spring assembly
between the rock shaft and pressure valve was eliminated. Quite a few of
the early systems were backfitted with the later style handle.
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