Jlg 800a tower lift cylinder removal .

[kenneth hofer]

Hey guys , new to this forum and would like to get some advice on removing the (huge) tower lift cylinder on the main boom . I do have the proper lifting equipment to support the boom itself while doing the job . i also understand that it a big job and can be very dangerous if not done right . But thats why i would like some advice from someone that has experience with this task . like how do you make removing the cylinder rods EASY lol and what the best way to get the cylinder out once its free . thanks in advance ..

 

[Txhayseed]

Do you have a way to hold the wieght of the machine boom up with out the cylinder? The way i do it is lift the basket about half way up. Pull a reach fork for under the basket to hold up the boom. Pull off the hydraulic lines and cap them. Knock the pin out of the rod end. Leaving my pipe i used to knock the pin out to hold up the cylinder. Put a chocker on the cylinder. Hook it the crane on my truck and apply pressure. Then remove the bottom pin and remove the cylinder. Thats how i do it. The removal process is covered in the service manual. I do like this since i have to remove the usually outside with my service truck and this allows me access with my crane. There are and have seen some people do it with the boom cribbed up parallel enough to gain access to the cylinder and room for removal.

 

[92U 3406]

Have fun with the pins. Every JLG I've ever touched cylinder pins are corroded solid into the frame.

 

[tractormech]

Have fun with the pins. Every JLG I've ever touched cylinder pins are corroded solid into the frame.

They can get seized up! The last one I did was an old 60HA boom scope cylinder. The base end was froze up tight in the frame. I discovered Milwaukee Diablo carbide tooth Sawzall blades. It did a number on the pin. I keep some on the truck at all times now. Kind of pricey but they work and don't take hours to cut. Just oil and saw. The two ends were froze up but only half as hard as getting the pin to move whole-that wasn't happening.

 

[kenneth hofer]

 

[kenneth hofer]

So cylinder number 3 is the one i have to reseal . We have a big hoist that raises 7 feet, i can use that to place underneath the upright.That way i can support it and move the boom up or down . We also have a overhead crane that i can then use to remove the cylinder with a sling . We have tried to get the upper pin out with a sledge hammer but it wont budge . Is there anyway i can relax the hydro preasure in the cylinder without draining out all oil ?

 

[Txhayseed]

You can remove the lines and cap the machine side. You wont drain the machine since the function manifold stops fluid flow. You would loose the residual from the lines and cylinder. Remove the holding valves from the cylinder and that will release any load the cylinder has left. but like everyone has said the pins can be a pita. You may get to to the point where you need to burn the pins out or cut them. Like tractormech said. They usually get stuck in the frame boss on one side or the other or both.

 

[Txhayseed]

I should note that make sure you have the boom supported and secure with its weight held securely. With the cylinder still pinned in place the holding valves are what keep the cylinder locked in its position. Once they are removed nothing is in place to keep the boom from feeling the effects of gravity and dropping

 

[Mike hofer]

For sure , thanks for all the info!!! I have no problem securing the boom in a sufficient manner . My only concern is getting the pins out with out to much of a hassle ... I will contact JLG and ask what kind of pulling tool they offer for a job like this .The pins have thread tapped in on the butt side on the pin . Have a look at the link i posted , i am thinking i could probably rent a tool like that somewhere . Maybe make life a but simpler .LOL

 

[tractormech]

Hayseed is telling you straight-This thing will kill you in a heartbeat if it falls. Once you have it blocked up and you take the lock valves out you are 100% dependent on the blocking.Once the pressure is off the pin may move.Just don't mushroom it and add to the problem. What size is the threaded hole?

 

[kenneth hofer]

Yes , I understand that once the holding valves are removed that gravity will do it’s thing . The thread size on the pin is only 1/2 “ . Just wondering why they would install thread that small for pulling, or even installing any at all.

 

[tractormech]

Getting that pin out may prove interesting.Those of us that deal with this have equipment to handle pin removal-a welder to weld a big nut to the pin,1 inch threaded puller rod,hollow ram porta powers and the like. I have an Arcair slice to blow holes in pins if I have to. Every job is different. just don't mushroom the pin by beating on it. This is a big deal if you haven't done this sort of thing before.How long is the pin? Diameter? You may get a bridge clamp and exert enough force to get it to move...don't know.It's awkward to get to and that adds to the issue.Just block that thing up good-you can't be too safe.

 

[MarshallPowerGen]

It can still be a pain, but if you can get the boom positioned (and supported) right and the top pin out, you can lower the cylinder and tear it down still in the machine if the bottom pin is too frozen.

Be weary of the holding valves, some spin right out, and some like to blast out and shoot across the shop (or punch a hole through the drain pan laid over it). Just take it slow and stay out of the way.

 

[kenneth hofer]

The pins are about 20” long by 6” long. I am thinking of first trying to heat up the pin with a torch and then apply liquid nitrogen to cool it of very fast . If I do that a couple time she should brake free . If not then I have a option of renting a hollow center enerpac Hydrolics ram from a shop in town.

 

[kenneth hofer]

Ya you don’t want to remove the holding valves while under pressure . (Very dangerous )!! You can actually remove them with the boom fully lowered , as there is a access hole behind the engine . Just have to push the engine forward , then that gives you plenty of space to unhook the lines and valves from the cylinder . You also have access to the pins from on the frame that way . So I was thinking of braking the pins loose while the boom is secured up and the upper pin accessible. Then lowering the boom and then pulling the pins. Once the pins are removed I can lift the boom up with our crane and hoist which will give me access to get the cylinder out with our loader and jib boom .

 

[92U 3406]

Just be prepared for a struggle. I've broken 10 ton press rods removing JLG pins half that size in diameter. Hot, cold, doesn't matter. You might get lucky but every one I've ever touched fought every inch of the way.

 

[tractormech]

You said 20 inches long but 6 inch diameter? Typo on diameter? If not that thing is massive.

 

[tractormech]

Just be prepared for a struggle. I've broken 10 ton press rods removing JLG pins half that size in diameter. Hot, cold, doesn't matter. You might get lucky but every one I've ever touched fought every inch of the way.

I pulled two on the slave cylinders on a 644b Lull that had been on the beach it's whole life. 1 3/8 x 6 pins. Welded 1 inch grade 8 nuts to the ends,ripped the nuts off three times so I blew a pencil sized hole through the middle of the pins with my Arcair slice. The pins actually popped like a rifle shot when I blew through. I've never had one do that. Welded nuts on again and that 30 ton porta power didn't want any more. It would do all it had and the pins would pop and move a tiny bit. They came out hard every inch of the way. And the rust....unbelievable. You just never know.

 

[kenneth hofer]

Sorry for misinforming you on the pin dimensions. The pin is 2 7/8 by 16 inches . i have attached some photos as well. Thanks .

 

[92U 3406]

I pulled two on the slave cylinders on a 644b Lull that had been on the beach it's whole life. 1 3/8 x 6 pins. Welded 1 inch grade 8 nuts to the ends,ripped the nuts off three times so I blew a pencil sized hole through the middle of the pins with my Arcair slice. The pins actually popped like a rifle shot when I blew through. I've never had one do that. Welded nuts on again and that 30 ton porta power didn't want any more. It would do all it had and the pins would pop and move a tiny bit. They came out hard every inch of the way. And the rust....unbelievable. You just never know.

I don't know what JLG puts on those pins but I have NEVER come across a machine as bad as them for seizing. They always seize in the frame, never the cylinder.