Nicholas Fluhart

December 25, 2011

Allis-Chalmers Forklift Cylinder Repair

Filed under: Project: AC Forklift,Trucks & Equipment — Nicholas Fluhart @ 5:30 pm

Well, after 30 years of service, age and wear had finally gotten to the hydraulic cylinders on my old Allis lift. You may remember previously I rebuilt the short lift cylinder and one tilt cylinder on the mast. Later, the long lift cylinder and the other tilt cylinder both began hemorrhaging. Bad became worse and soon I was loosing a gallon of fluid at every use. Fortunately, I had recently acquired a little Clark lift which took up most forklift duties around the complex. This bought me a little time for the repairs.

After the local hydraulic shop, in a state of incompetence, screwed up my short lift cylinder, I decided to rebuild this one myself. Rebuilding the long cylinder is no easy task for two reasons. One: Due to its location within the mast (not to mention its weight), it is heck to remove and reinstall. Two: It is also more complex than the short lift cylinder as the long cylinder has a feed tube with all the associated bushings and seals. At first glance, there’s no logical strategy for getting it out, and since my service manuals don’t cover anything to do with the mast, I’m flying purely on what I hope to be at least a moderate level of competence in terms of my skill level. Nevertheless, I endeavored to persevere.

Since I figured the mast would have to be raised at some point during the procedure, I had to work on it outside the shop. I began by removing the hydraulic line attached to the feed tube. Then I removed the nut that fixes the feed tube to the top stage of the mast. You’ll note that I’m using a manual ratchet instead of an air wrench on this because the nut is self locking, and often times if an air wrench is used, it will destroy the threads because of the high rate of speed.

Hydraulic Line Removed from Feed Tube

Removing Feed Tube Nut

Might I add, the humidity level that day, and throughout most of the project, had to have been 200% if that’s even possible, which explains the somewhat foggy photos and my drenched shirts. Moving on… Next, and before loosening anything else fixture-wise, I decided to loosen the gland nut while the cylinder was still firmly in place. I didn’t have a wrench big enough, so the next day I borrowed a large chain wrench which did the job nicely.

Feed Tube Nut

Loosening Gland Nut

Next, I had to raise the mast so I could lower the junction block at the top of the feed tube through the second stage of the mast. For this I took my Clark lift and raised the carriage on the Allis lift until the second stage of the mast begun to raise. This was NO easy task. The Clark lift would barely handle the weight. To make matters worse, the junction block is slightly offset and refused to go down through the hole in the second stage. Careful not to bend the feed tube, I pried and hammered a bit before logic struck at which time I decided to loosen the bottom mounting nut on the cylinder (exactly like the top nut on the feed tube). This allowed some wiggle room, and alas, it dropped through and the top of the cylinder was now completely free.

Feed Tube Junction Block

Raising the Mast

The next step in removing the cylinder was to finish the bottom mount and unhook the bottom hydraulic line, but first I made certain the mast was safely suspended. Don’t let the compact size of this machine and these parts fool you; this stuff is very heavy. The machine weighs about 13,000 lbs, and the mast components are made from very thick and very heavy steel. There is literally a ton of weight hanging above me here, so safety is very important. I used a strong, heavy-gauge pipe to hold the mast up, then I chained the top portion of the mast for a backup safety mechanism. I also had the carriage double chained.

Safety Check

When attempting to unhook the hydraulic line from the base of the cylinder, it became evident that there was not enough room to maneuver the wrench in the tight space. So I decided to unhook the line back at the hydraulic valve. This would give me slack enough so when I removed the cylinder I could pull the base out far enough to use the wrench to remove the line from the base of the cylinder. Back at the valve, I also had to unhook and move the hydraulic filter to have enough room to work at the valve.

Filter Moved Back from the Valve

Disconnecting the Bottom Hydraulic Line

Finally, the heavy cylinder was ready to come out.

Now that the cylinder is removed, it is time to disassemble the components for inspection at which time we can also take measurements which will be needed to order the new parts. We place the cylinder down where we can easily work on it and remove the main gland nut, and then the main ram easily pulls out of the bore. Then, using the same chain wrench, we remove the feed tube gland from the ram, and the feed tube pulls out. Then, although it’s not pictured, we removed the feed tube gland which proved to be extremely stubborn to slide off the tube, but a long pipe and a sledge hammer did the trick.

Loosening Feed Tube Gland

Removing Feed Tube from Ram

Once everything is apart I can begin measuring the components to place an order for new packing. I couldn’t simply measure the old seals because they had completely disintegrated. This explains the hemorrhaging, and it also explains how rainwater was entering the hydraulic system. Nevertheless, I took measure and proceeded into the office to do what the incompetent local hydraulic shop said was impossible: find new seals. After approximately one Google search and three minutes of viewing an online catalog, I easily found the parts I needed and placed the order. Since my application has a feed tube involved, it required the most expensive packing kit. This is largely due to the addition of bronze bushings and extra seals. However, it was still much cheaper than anything the local guys could have ever came up with and I was happy to find the parts. Now, on to the business of reassembling the cylinder…

First we took the feed tube gland and knocked out the old plastic bushings and replaced them with the new bronze bushings that came in the kit. We used the hydraulic press to install the new bushings:

Installing Bronze Bushings

Reinstalling the gland back on the feed tube proved almost as difficult as removing it. We used a brake cylinder hone to reach precisely the correct inside diameter of the bronze bushings, then we used a buffing wheel on a Dremel tool to polish off any scars on the chrome feed tube. After that, we were able to slide the gland back on the tube with moderate pressure. Then we installed the feed tube back into the ram, and after installing the new wear ring / guide band,  we reinstalled the ram back into the cylinder. Once completed the final step was to install the new oil seal and dust seal into the main gland nut.

New Oil & Dust Seals for Gland Nut

With new oil and dust seals in the gland nut, it’s time to install the nut back onto the cylinder, and it is a tight fit over the feed tube gland and ram. To keep from destroying the new seals, we placed a spacer on top of the gland nut and then used two bolts through two flat bars and threaded them into the top of the feed tube gland. This slowly pressed the gland nut onto the ram without damaging the seals. And that concludes the assembly of the cylinder.

Installing Gland Nut

Cylinder Assembled

Now, before reinstalling the cylinder onto the forklift, we needed to paint it. Jose uses a wire brush to strip all the old paint off. Then he masks off the chrome before applying primer.

Stripping the Old Paint

Applying Masking Tape

To conclude, I come in behind him with a new coat of gloss white industrial enamel. We then reinstall the cylinder in the same sequence used to remove it. The final step was to refill and bleed the hydraulic system and give the machine a good scrub and wash.

Applying a Coat of Industrial Enamel

Finished and Back in Service!

Everything worked out great bringing us to the conclusion of this project. My Allis-Chalmers ACP 80 is back to work and running great.

Until next time…

4 Comments »

  1. do you have any pics or any direction on how the seals go into the glad nut? i just bought a new seal kit but what i pulled out compared to what i got in the kit is not the same.. thank you?

    Comment by Levi Bishop — July 23, 2012 @ 12:36 pm | Reply

    • I know this is an older comment; sorry I missed it. Typically the main oil seal in the gland nut is a type of thick o-ring that fits in a groove inside the nut. Then you have a dust seal that goes on top, and it’s typically a lip seal. I’m not sure exactly what you have, but that’s normally how it goes.

      Comment by nfluhart — September 20, 2012 @ 12:52 pm | Reply

  2. I have a Allis Chalmers ACC80 that has a bad mast cylinder, did your cylinder have a leather packing at the bottom of it or did it just seal with the upper gland seal?

    Comment by Nick Jockheck — July 12, 2015 @ 6:50 pm | Reply

    • Are you referring to a tilt cylinder or a lift cylinder? In any case, I don’t recall a leather packing. On the piston, there will be a seal and a guide band (or wear ring). On the gland nut there will be an o-ring oil seal of some type and also a dust seal. You’ll see in one of my lift cylinder posts, the long one also had a feed tube with a seal and bronze bushing.

      Comment by nfluhart — August 26, 2015 @ 9:27 am | Reply


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