john deere 490D cylinder repair question

rmg · Dec 16, 2015

Have a john deere 490D excavator. Am trying to repair top cylinder ( arm cylinder ). I have it apart but cannot budge the nut on the end of the rod. Does anyone know if nut is right or left handed? I did remove the set screw and ball from nut, but still won't move. I've never seen one with left hand threads, but I don't want to mess this up. Thanks for any help.

NCWayne · Dec 17, 2015

Even though those nuts use a ball and setscrew to keep them from backing off, they are still TIGHT. I just did the boom, and dipper cylinders on a 120 Deere excavator which is similar in size, just newer. If I remember right the nuts on the 120 cylinders were torqued well North of 600 ft lbs.

Short of having some kind of cylinder bench and a way to get that much torque, your pretty much stuck taking it somewhere that has that capability to get the nut loose as well as retightened.

Wish I could give you better news, but without a cylinder bench and a torque multiplier, your pretty much out of luck.

rmg · Dec 17, 2015

Thanks, NC Wayne. I live in rural area of east Texas and not close to most shops that can do this. BUT, there is a guy about 40 miles from me who works on cylinders. He looks like a reject from a motorcycle gang with all the tattoos and Harley T shirt but he does know what he is doing. Took it to him today and he showed me the bench he uses and how he gets the nut off. Will see if he really can! Thanks for your help.

tlock0331 · Dec 18, 2015

rmg,

Most times, on cylinders from them ol hoes, the tube and nut are usually ruined getting them apart. I have taken the outter sleeve off and heated the tube and hit it with both an air hammer and a 10" compound pipe wrench, mixed results at best. For a 690 its about 3500 bucks to replacement the entire thing, used are almost impossible to find....

That being said, i would start looking around for a cylinder about the same size to replace it. I found my dipper cylinder replacements from an old trash truck, i had to cut the ends off and weld new on, but that only cost me 100 bucks for junkyard cylinders and new slugs for the pins. If you go that route...remember this, the cylinder fits UP INTO that pin assembly, so if your replacement cylinder is a little bigger around than the one you have, put in a spacer block to raise the pin other wise you have to trim the pin assembly, which is a lot bigger pain than welding your pin eye an 1 inch offset haha

Heat Houser · Dec 21, 2015

It has standard RH threads and has a fair amount of torque. A cylinder bench is the only way to go. I have built a bench in the past that would do 20,000 ft lbs which would get the nut on an EX1800 Hitachi Mining shovel.

The EX5600 has about 55,000 ft lbs on the arm cylinder as I recall.

The nuts are highly torqued but a 490 is way less than the larger machines.

I think the 490 was the Hitachi EX120 but cannot recollect for sure.

john deere 490D cylinder repair question

rmg

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NCWayne

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rmg

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tlock0331

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Heat Houser

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