I don't know about Allis forklifts, but I've got a couple Clarks and a Hyster of similar vintage, one of them uses a complex packing system, one uses a simpler system, and one uses just a 'displacement cylinder'... where there's no piston rings, it's just a guide for the inside end of the rod.
Your Allis MAY be just a displacement cylinder... if you're not familiar:
Displacement cylinders are particularly popular on long-stroke hydraulics. The first one I ever worked on was on a 3-stop hydraulic in-ground passenger elevator... and I grew to appreciate them once working on my first forklift, for reasons to follow-
On a displacement cylinder, the packing really just consists of a couple O-rings and spacers within the cap, and a wiper-type dust seal on the top. The packing is all in the cap assembly, and there's a void between the upper wiper and the pressure packing... the void has a drain line that returns (gravity) to the reservoir.
The advantage of a displacement cylinder, is partly the simplicity.
A displacement cylinder's bore does NOT need to be perfectly straight or smooth... there's no tight tolerance necessary for the end of the ram (usually referred to as the 'stop') because all it does, is stop the cylinder from spitting all the way out of the cylinder. A slight bend in the rod imposes no significant issue to the unit's operation... and flex in the system doesn't seriously stress the displacement cylinder.
There's no need for a 'vent' on a displacement cylinder- there's no 'piston', so you don't have an entrapped volume 'behind'. The ram extends simply because the cylinder is filling up with fluid, and the only thing that will make space, is the ram being displaced out. Furthermore, it will tend not 'suck in' dirt or crud from atop the packing, because there's never any negative pressure on the seal. Whatever dirt DOES happen to make it past, will either be pushed out on the next cycle, or washed down the drain line into the reservoir, to be stopped by the filtering plan.
A displacement cylinder is much less susceptible to rod corrosion, because when retracted, it is fully submerged in fluid...
And finally... A Displacement Cylinder can USUALLY be re-sealed in-situ. ON a forklift, here's how you do it:
Raise the mast up about a foot'n a half, put blocks under the carriage, so it can NOT fall.
Disengage the cylinder from the hoisting crosshead. Usually, this is a bar with sprockets for a doubled-over chain, but this totally depends on the machine. Usually, the rod has either a big castle nut, or a bolt-pin, or something that retains the crosshead cap on.
Once the crosshead is disengaged, chain it securely into the mast, so it cannot come down.
Lower the rod into the cylinder about halfway... scrub the rod with wire brush, emory cloth, etc so it's smooth and clean, wipe it down, and spray on a little oil (like engine fogging oil)
Lower the rod all the way down...
Remove the drain line, then disengage the packing assembly from the top of the cylinder, slip it up over the rod. IF it doesn't wanna lift, fire up the engine, and cycle the valve to lift slightly. Don't rev it up, if it blows the packing out, you'll get a 'drilling rig shower'. a little bump of the valve will usually unseat the packing, and once free, it'll ooze some oil down the exterior, but the packing will slip off. At that time, you can carry the packing into the shop to clean and rehab. Easy-Peasy... with a stepladder. Mine took me about an hour and a half.
SO... if you happen to find a diagram, but there's no seals shown, it's probably a displacement type. If you carry the entire (cleaned and reassembled) packing, along with your cylinder's OD measurement to a hydraulics shop, they can order all the proper O-rings, and usually the modern materials are even better'n the old.
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