I've got the same mast with a leak at the gland nut on one of the outer lift cylinders. Were you able to fix yours on the truck, and if so, how did it go? Anything you learned that I should be aware of?

yeah i've dealt with these before and seen the guys in the shop take these apart and that extra channel just takes up more room so workable space is even smaller so removing those main cylinders is even tighter. The problem is in the crossbars at the top and middle that get in the way when trying to pull the cylinder out, that's why if i didn't have to repack the whole cylinder i just did the gland nut at the top if it was just leaking and not drifting down.

Thanks for the info. I have completed many three stage outer cylinders, but never a quad. I was a bit concerned with the removal of the cylinder. Usually do remove the entire cyl. and reseal the rod piston just to be sure it will not leak, but in this case if it gives me to much trouble, perhaps I will try just the gland or nut seals as you call it. My customer wants a price upfront, I will cushion it just in the case it takes 6 to 7 hours. Thanks again!

on a quad mast 4 to 5 hrs would be if everything went perfect and you've done it many times before and knew exactly how to do it.
For a first time attempt i would add a couple hr's to that.

The freelift cylinder is usually easy to do, no issues getting it out as it is with any freelift cylinder. The outer "main" cylinders are a whole different story. The manuals all suggest removing the mast and laying it down to remove or repair any part of it which i'm sure they suggest this for safety reasons.
But with that said it can be done on the truck if you have the right tools to block or chain up the mast sections after you raise it to the right point to allow the cylinder to clear all the areas so it will come out. With these quad masts you have that extra channel so there is more weight to consider when blocking or chaining up the mast sections so use a heavy chain. Of course if there are any attachments on the front those will have to be removed to lessen the weight.
If indeed you actually need to repack the cylinder completely then the rod will have to be removed so you'll need to actually remove the whole cylinder to change the seal on the rod along with the packing nut seals. In alot of cases if the upper packing nut seals are the only place it is leaking you do not need to remove the cylinder, just raise the mast, block or chain it up, disconnect the cylinder rod and use the hydraulics to lower the cylinder rod enough to get the packing nut off. Then just replace the seals in the packing nut and reassemble it in the reverse as you took it apart. (keep in mind there is a crossover tube that runs from one cylinder to one of the other ones so that will have to be removed and the fitting removed from the cylinder rod as well).
Without removing the cylinder then yes you can do it in half the time that was suggested as long as you use extreme caution in safety measures for securing the mast channels.

Thanks! Much appreciated.

The manufacturer of the mast is Lift Technologies. Their web site address is Lift-Tek dot com. The have service manuals listed in the support section. Just a guess but i would expect it to be a 4 to 5 hour job. If you call them I'm sure they will assist you.