JD 7775 curl cylinder
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    56FordGuy's Avatar
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    JD 7775 curl cylinder

    I had to rebuild a curl cylinder today, took a few pictures.



    I have a vise, but preferred to let the machine hold the body while I broke the gland it loose. I removed the ram pin, swung the cylinder up and broke the nut loose with the body still pinned to the boom arm. It requires two 9/16" wrenches to remove the bolt that secures the ram pin. I didn't measure the size of the end cap, but it has two flats on it to use a wrench. I used a 48" pipe wrench and needed every bit of leverage it offered. Once it broke loose I was able to turn it out by hand.



    The body pivot is held by a 1/2" bolt. You'll need a pair of 3/4" sockets, one on an extension. The outer bolt is inside the boom about 4". Once you remove the bolt you'll have to knock out the pin that it's holding in.





    Undo the lines and take it to your vise. With the end cap unscrewed, pull the ram out.



    The ram. To remove the piston you'll need a 1 1/8" socket or wrench. Do not clamp the rod surface in the vise.



    With the piston off, slide the end cap off. Clamp it in the vise by the flats, not the threads. Remove and replace the seal, wear ring, wiper and oring.







    Slide the end cap back onto the ram, then reattach the piston. Note that one side of the piston is made to sit over the ram, be sure you reinstall it facing the correct direction.







    With the piston securely attached, pull the seal and wear ring off. Install the new wear ring first so that the seal doesn't get stuck in that groove when you put it on.



    Slide the ram back into the body, then tighten the end cap. You don't have to crank down on it with a 4' wrench, just get it tight.



    When you go back to the machine, install the body pin first, then extend the cylinder by hand and install the ram pin if you can. Do that before attaching the hoses or it will air lock and you'll have to have the machine running to extend it hydraulically. Once everything is reassembled, run the machine and cycle the curl function 5-10 times to push a put any air. When you first lift the boom, don't be concerned if the bucket drops forward before you curl it. That's just the air in the cylinder being compressed and cycling it will push all that out.
    RandyM, Gizmo2, pcabe5 and 9 others like this.
    -Blake

    Your mileage may vary.

    JD 6410
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    Official "Groovie" Dude
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    Great tutorial.👍
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    Senior GTT Super Slacker Gizmo2's Avatar
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    I have a vise, but preferred to let the machine hold the body while I broke the gland it loose
    That's a good idea.
    Nice job, thanks.
    pcabe5 and 56FordGuy like this.
    Keith

    JD 2320, 200CX FEL/61" bucket , 46 BH/16" bucket, Artillian Forks, 72" Snow Blade, Landscape Rake, Ballast Box, PHD, The Wife
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    Let me grab my Craftsman 107 piece tool set and I'll get right on that.



    Seriously, great work.

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    56FordGuy's Avatar
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    Quote Originally Posted by Gizmo2 View Post
    That's a good idea.
    Nice job, thanks.
    A guy has to learn to be creative doing field work. My vise is not even close to being strong enough to hold the cylinder to break it apart.

    Quote Originally Posted by steveontheridge2 View Post
    Let me grab my Craftsman 107 piece tool set and I'll get right on that.



    Seriously, great work.
    No reason you couldn't! I think, aside from a big wrench for the end cap and maybe a seal pick that 107 piece set probably has everything you would need.

    Had a call this afternoon for a steering problem on a 55 ton off road hoist. The steer cylinder blew the internal seal and is bypassing. The ram is 6.5" diameter, four feet long and the entire cylinder assembly is close to 900 lbs. That's going to be a fun one.
    -Blake

    Your mileage may vary.

    JD 6410
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    xcopterdoc's Avatar
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    Worked the field for 15 yrs. Always an adventure! I loved it. Nice job and good write up! I called that series the old Deere four number's. Made by New Holland and tuff as nails. Only thing I didnt like was having to tip the cab without the special fixture. Could get a lil hairy.

    Sent from my LGL52VL using Tapatalk
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    Very good write-up. Done a few in place on my Bobcat machines the same way. I've been buying the repair kits off ebay for 20 to 30 bucks apiece rather than the 80 to 120 bucks from the dealer. Plus the nearest dealer is like 80 miles away.

    Here's a couple pics of the cylinders we've been changing out on our cranes offshore. We haven't repaired any ourselves, but we've changed 16 of them so far. Note the size compared to the people in the pics. There's a guy on top of the crane boom in the second pic. The pin that goes in the clevis weighs over 600 lbs.
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    Serious cylinders

    Quote Originally Posted by mtrmn View Post
    Very good write-up. Done a few in place on my Bobcat machines the same way. I've been buying the repair kits off ebay for 20 to 30 bucks apiece rather than the 80 to 120 bucks from the dealer. Plus the nearest dealer is like 80 miles away.

    Here's a couple pics of the cylinders we've been changing out on our cranes offshore. We haven't repaired any ourselves, but we've changed 16 of them so far. Note the size compared to the people in the pics. There's a guy on top of the crane boom in the second pic. The pin that goes in the clevis weighs over 600 lbs.
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    Now those are real cylinders. When it takes a crane just to lift the cylinder, you know it's big time. . .

    Treefarmer
    John Deere 790, 300 loader w Ken's Bolt on Hooks & Piranha tooth bar, grapple, back blade, box blade, Bush Hog mower, couple of red tractors, hay equipment, various old stuff some red, one orange, some I don't remember

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    Quote Originally Posted by Treefarmer View Post
    Now those are real cylinders. When it takes a crane just to lift the cylinder, you know it's big time. . .

    Treefarmer
    If I remember correctly the main boom cylinders pictured are about 22k lbs. I you notice in the picture of the crane itself, there's a large black stain on the bottom of one of the cylinders. This is the one we were preparing to change out. On this particular crane, no other crane can reach that cylinder so we had to come up with some very inventive rigging to change it out. Took about 3 24-hr days for that one. We have now changed every crane cylinder on the rig. 4 cranes x 4 cylinders per crane = 16 in all. By the time were through we had the time down to about 36 hrs. to do one cylinder.
    ETA: we were changing out the complete cylinders and sending them to be rebuilt, not overhauling them ourselves.
    Last edited by mtrmn; 11-23-2016 at 08:45 AM.

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    Location?

    Quote Originally Posted by mtrmn View Post
    If I remember correctly the main boom cylinders pictured are about 22k lbs. I you notice in the picture of the crane itself, there's a large black stain on the bottom of one of the cylinders. This is the one we were preparing to change out. On this particular crane, no other crane can reach that cylinder so we had to come up with some very inventive rigging to change it out. Took about 3 24-hr days for that one. We have now changed every crane cylinder on the rig. 4 cranes x 4 cylinders per crane = 16 in all. By the time were through we had the time down to about 36 hrs. to do one cylinder.
    Are those hanging over the edge of the rig? It looks like s substantial distance up to the boom so creative rigging might be an understatement. I can't imagine having to figure out lifting the equivalent of a dump truck that's high in the air without a crane. My hats off to you and your crew.

    Treefarmer
    56FordGuy, BigJim55, mtrmn and 1 others like this.
    John Deere 790, 300 loader w Ken's Bolt on Hooks & Piranha tooth bar, grapple, back blade, box blade, Bush Hog mower, couple of red tractors, hay equipment, various old stuff some red, one orange, some I don't remember

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