Please help!, I recently purchased a lull 644d-34 and the automatic fork leveling does not work at all, I wanted to know if you know what this might be, some possible fixes thank you in advance
I don't have the schematic for the 644D but I looked at one for the C-series which I'm assuming are the the same in this regard. The slave cylinders are simply tee'd into the line for the carriage tilt cylinder. Assuming you can still make the forks go up/down with the joystick then the slave cylinders have either been disconnected or the piston seals are blown out. ISZ
Will the forks operate normally with the joystick? If so I agree with ISZ. I'd repack the slave cylinders. It sounds like the piston packing may be blown. BUT- before you start tearing cylinders apart check the hoses on the slave cylinders. Make sure someone hasn't crossed the lines. The bottom ports should be hooked to the same line as should the tops. If they got crossed you won't have any self leveling. I've got that hat. Good luck.
Good point on crossing the hoses - didn't think of that. They could have also hooked the slave cylinder rod ports to the carriage base port and vise versa - but in this case the carriage would tilt back when hoisting. ISZ
It would do that. I ran into the crossed line situation on a 644B-37. The slave cylinders were hooked up with the base of one going to the rod of the other one. Self level was rendered inoperable.
I do not remember what came after the 644 on the last one I worked on. However a service manual was on line for free.
My 644d-34 fork leveling went intermittant, then went out right after getting my boom hoses replaced. Are the slave cylinders the two cylinders above and behind the boom cylinder? My Lull has been in the shop for 6 months and they can't figure it out. I may be bringing it home next week, as I think they are fixin to wash they hands of it. Back when I took it to them, I didn't have time to tinker with it. Now I do have time. hugs, Brandi
Those are the slave cylinders. If the packings are blown inside you won't have automatic fork leveling. Double check your plumbing on the boom hoses. But intermittent operation and then failure sounds like cylinder packings.
Thanks. I got the hydraulic diagram and that sure looks like an simple circuit. Hope to have it home next week, then will pull those cylinders and get them tested. Thanks again! hugs, Brandi
I took the slave cylinders off and sent them out for rebuild. I would have done it myself, but wanted a professional to check it out for wear. I installed the slave cylinders, replaced the hyd. return and pump (is it called charge?) filters. I cut the filters open and I only saw small particles of carbon. Some flea size, but mostly looking like pepper. I added about 8 gallons of hyd. fluid and cranked her up. When I lifted the boom, the fork tilt up and down did not move at first, then it did an uncommanded full down. I shut her down. Today, I just fired her up to see if the electric button was working on the joystick. I hit the button and moved the joystick to the right and the traverse carriage moved. I returned the carriage and shut her down. So the electric button on the joystick is working. Is there something I didn't know to do with bleeding the slave cylinders, or should I take it to Lonestar Forklift and let them figure it out? hugs, Brandi
I finally got the slave cylinders working right. The last guy that worked on it had both cylinders lines crossed. I then held the tilt button until the forks moved. Then all was good.
Duplicate post
I have a 644B telehandler its 1998 . The forks won't self level since we purchased it. Read on here to check the slave cylinder lines and they were both crossed but after un crossing them they still aren't functioning. What would be the next step ? I had one with both lines crossed on both sides we swapped them out and still nothing. Is there a procedure? To get them working
Remove the lines on one slave cylinder and plug the lines. Then try if the forks auto level. If not, remove the plugs and replace the lines to that cylinder. Do the same to the other cylinder. If both cylinders (one at a time) do not auto level, remove both cylinders and have them rebuilt. If one works and one doesn't, I would rebuild both at the same time. Be real careful one side's lines are correct and the other side's lines are crossed. I am waiting for a heavy equipment welder to come out and reweld the right slave cylinder's lower mounting ear back to the frame. Only thing I can reason why the ear broke off.
I have a 644B telehandler its 1998 . The forks won't self level since we purchased it. Read on here to check the slave cylinder lines and they were both crossed but after un crossing them they still aren't functioning. What would be the next step ? I had one with both lines crossed on both sides we swapped them out and still nothing. Is there a proce So your thinking the cylinders seaks are blown ?
Are you sure that both were crossed? You didn't accidentally cross them the other way? It's easy enough to overlook. If you have no automatic leveling at all there's still a crossed line or the slave cylinder piston seals are completely blown. You can get some #8 JIC plugs and plug the lines to one slave cylinder and see if it tries to level somewhat. If you raise the boom and the forks level up instead of down the lines on that cylinder are crossed. Double check your slave cylinder plumbing and let us know. Good luck.
Is one side supposed to be crossed and the other not ?
Yeah they were both crossed. We unhooked them and re attached them and still nothing I was wondering if it had aur or needed to be bleed
No, then the slave cylinders would be fighting against each other. It takes both slave cylinders working together to keep the forks level.
Raising the boom up and down and tilting the forks will get the air out. Both bottom ports need to be together, and naturally the top ports as well. If they aren't like that you are simply transferring fluid from the bottom of one cylinder to the top of the other. There's no oil being forced out to the tilt cylinder to make it automatically level. I'm leaning hard to a line is still crossed.
Ill check again tomorrow but im positive we corrected that. Im gonna then try unhooked each separately and capping off the other and vise vs. If that dont work i guess the cylinders are blown. The one is Slightly wet
Let us know what you find. Good luck with it.
Both lines are good not crossed . Still not functioning so im goin to the hydraulic line store to get caps so I can try each separately.
Welp switched the lines. And to my surprise it ripped the head off one of the slave cylinders
Switched the lines? You said you were going to get plugs for the lines and test each cylinder seperately. Did you put caps on the cylinder fittings AND plug the lines to the cylinder that tore the head off?
Not yet were gonna remove it this weekend. Not the actual head but the ear that mounts to the machine tore off. Really odd
sent you a PM.
Like this?.............
Yeah the upper part on the boom snapped off
How about a photo or two?
Frame tilt stopped working on mine
Does anybody have a picture of the slave cylinder? When I raise my boom my forks tilt and when I lower it goes down. Base off the comments I would believe that the lines got crossed at the slave cylinder ?
Thank you