Working on a Gehl 5640E with what I initially thought was a twisted/racked boom (cutting edge wearing thin only on one side). Hits bump stops at 3/8 to 1/2"" intervals. I've had to re-twist these in the past when boom was racked from hitting a bucket corner on a curb or manhole cover at a quick ground speed, but this one measures out fine in those areas. Takes very little effort to twist boom into proper alignment with the only abnormality being the right and left lift cylinder rods measure close to 1/2" difference in any position except all the way lowered. My question is this: Could one of the lift cylinders be fatigued internally so that it isn't exhibiting the same amount of pressure as the opposite side? Neither are leaking externally. These machines have an extraordinary amount of hydraulic power for their size and I'm wondering if it was in a situation where one cylinder suffered internal damage to a seal. Boom does drift a very slight amount when up in the air and engine off.
Highly unlikely. You say the boom is straight? the mounts must be bent if it doesn't go up and down evenly. The only way I can figure the cylinder would affect this is if one is dragging bad inside, or one is ballooned out. Take a circumference measurement of the middle of the cylinder, or use a caliper if you have one with enough reach.
If the piston seals are bad, the cylinder becomes a displacement cylinder with only the area of the rod supporting the load, so yes it's quite possible for one cylinder to be pushing with less than half it's usual force.
The rod end holes do get stretched out and ripped open. Pistons do work their way loose also
Hadn't thought of that. Wouldn't that usually leak both ways and not let the loader lift up the front wheels then?
Well, it depends. If it's a single seal it should drift both ways yes, but If the piston is the better type and has a seal in each direction, the one that takes all the punishment, lift in this case, will usually fatigue first. Sometimes even the single seal ring will be worn on the back edge from moving under pressure where the front edge is still in good condition. YMMV
Very helpful info. Thanks all! Pretty sure cylinders are at fault on this machine. These booms are built tougher than most.
Ended up boom was twisted. Found out by pulling both lift cylinder pins at the boom and lifted the boom in the front middle between quick attach plates with a single fork from another skid...held same measurements. SO I left the boom cylinder pin out on the high side, chained it underneath the body and attached to the upper tower in the rear. Installed the boom pin on the low side, used two 10 ton porta-powers along with the machine's pressure on the boom cylinder (30 tons of hydraulic force????). Better, but was only able to cut the twist in half...has 1/8 to 3/16". Had the low side almost 4" higher than the high side when under pressure. No heat involved. Geesh, incredibly stout and resilient. No idea how the guy twisted this.
I've said it here before and I'll say it again, operators are like peanut butter, they come in two flavors...smooth and crunchy. I've had to "un-tweak" twisted loader arms from crunchy operators myself.
Question though: Did you in fact test the cylinders and they passed muster? A duff cylinder will over time cause exactly this sort of twist, just sayin'...
Good question. Perhaps I should check it.