644 tt 34 Lull boom cylinder

[David Sargood]

Hi all, new to this site, looks to be an awesome place!
I am in the process of buying a 644 tt 34 Lull that has a leaking boom cylinder. I have rebuilt cylinders before just nothing of this length (it's about 10' long)
It appears as though the cyl has to come out the rear of the boom and I've heard there are some equalizing valves on the cylinder that could have residual pressure.
My main question is will I have to remove these valves or can they be left alone?
The other question is does anyone have any advice on getting the cylinder out of the boom?
The machine is about 3.5 hrs away from me so I'm just going from memory here and what I saw the other day when I went and looked at it.
I guess the third question is should I just look for another machine?
Thanks,
Dave

 

[joestewart]

My 644's boom extend cylinder has leaked for years and I need to do the same rebuild as you. I've been putting it off. I dread the thought of removing that cylinder.

The procedure is given in the service manual. Go to the following link. The procedure is on page "4.2-5". You have to level the boom by resting it on a support and you will probably have to hang a "come-a-long" from the ceiling to support the cylinder after you slide it out the back. Cylinder is too heavy to handle while standing on a ladder, even with a couple of guys. Maybe some of the more experienced forum participants can offer some helpful tips. Follow the procedure in the manual to deal with possible residual pressure in the cylinder. The cost of the parts is minimal (I think $40 for the cylinder rebuild kit), but its the labor that I dread.

Here's the link to the manual. Let me know if you have trouble accessing it:

https://drive.google.com/drive/folders/0B9-7bn5CX9NDUUt3YkJtQ1U0LWs

Should you buy it? Depends on how much he's asking! If its a bargain, I would go for it.

https://drive.google.com/drive/folders/0B9-7bn5CX9NDUUt3YkJtQ1U0LWs

 

[David Sargood]

Joe, thank you for that information and manual I'm sure it will come in handy. Yeah it looks to be a dirty job but one that needs doing. It's leaking bad enough that I would like it fixed. It's not just a drip but not really a stream if you know what I mean.
My thoughts for removal are prop the boom as they say and set up some scaffold and planks with a couple of guys or use my Kubota bucket and a sling to slide it through. I think the sling idea may be best. I'll have to get it on level ground at the job site.
I can pick this one for 8k and about 1k to get it shipped to the job site. I think that's a decent price what do you think?
thanks again,
Dave

 

[joestewart]

I was thinking it would be cheaper than that, given the leaking cylinder and who knows what else is wrong with it (you will probably discover other deficiencies in your first few weeks of ownership). I just perused the online auction and Craigslist and yours looks to be one of the cheapest ones out there. Not sure I would call it a bargain, though. I bought my 644 nine years ago for a lot cheaper (but it was a basket case).

 

[David Sargood]

Well I got the Lull delivered to the jobsite Friday evening (about 8pm..lol)
After using it for a couple of days I don't think it's the cylinder seal leaking, it only leaks while it's running. If it were the cylinder leaking wouldn't it leak when using it and when parked? It leaks even if I don't use the boom extend/retract cylinder. I'm hoping to get a few minutes later today I'm going to set it so I can stand on flat ground and look into the boom with a flashlight and see if I can see anything going on. From what I understand the hydraulics are controlled by pilot pressure, could some part of that or a hose be the culprit?

 

[Vetech63]

Well I got the Lull delivered to the jobsite Friday evening (about 8pm..lol)
After using it for a couple of days I don't think it's the cylinder seal leaking, it only leaks while it's running. If it were the cylinder leaking wouldn't it leak when using it and when parked? It leaks even if I don't use the boom extend/retract cylinder. I'm hoping to get a few minutes later today I'm going to set it so I can stand on flat ground and look into the boom with a flashlight and see if I can see anything going on. From what I understand the hydraulics are controlled by pilot pressure, could some part of that or a hose be the culprit?

Anything inside the boom could be the culprit. Hoses, fittings, orings, or the cylinder head seals. It would be best to clean out the area as best you can and have someone run the boom in and out while you watch inside there with a flashlight.

 

[David Sargood]

Well she started leaking/gushing a lot on Thursday so I think she is going to be out of commission until I get it repaired. Wish me luck. I didn't look inside yet but i will Monday when I get back to the jobsite.

 

[David Sargood]

I got my seal kit and have a rental unit coming in for a week or so. I may have the driver bring mine home, it will be much easier for me to work on it here. i have a big compressor and all the tools here too. We'll see.

 

[David Sargood]

Well me and a buddy tore into it today. I am happy to say all went well and it's operational.
The cylinder is 14'-8" long and weighs over 300lbs
I'll have to have it hauled back to work next week.
Cylinder coming out

cylinder ready to go in

Didn't really have time to take any more pictures, between the rain, humidity and the grease I had my hands full.