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JD 48 back hoe bent cylinder shaft

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andywoj
Join Date: Jul 2003
Posts: 6 Caledon East, Ontario Canada
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2003-07-15          59575

Hi,

I just went through two cylinder rods on the bucket cylinder on my 48 backhoe which is just over two and a half years old. I was removing tree stumps in a 4 yo 8" dia. range. The first rod bent like a pretzel. I had to cut the shaft with a hack saw and destroyed the nut trying to remove it. I was quite suprized to see an indent in the rod from where it had jammed against the nut. I replaced the rod and nut and proceeded to remove more stumps. At stump number five the rod bent again. Now I am really pissed off. My dealer told me that JD would not warrant the first rod and that I had abused the back hoe. This back hoe has approx. 15 hours of use. I decided to call JD customer support and had a discussion with the Canadian service manager reguarding my problems. He stated that there is no problem with my aplication and this should not have occured. Now if you remeber earlier I said I cut the shaft off with a hacksaw. The material that the shaft is made from is very soft and appears to be Supperior Shafting. I purchased a length of hard chrome shaft and made up my own shaft. You will not cut this shaft with a hack saw. I feel this will solve the problem. I did this because I felt that replacing the shaft with a third JD part would end up with the same result. I was of the understanding that all cylinder shafts where made from hard chrome shaft. It does not appear to be the case with the JD 48 back hoe. I am still waiting to see if JD will do anything to back there product.


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JD 48 back hoe bent cylinder shaft

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Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
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2003-07-16          59593

Jeff, sorry to hear of your troubles, I can only assume from where you are located that you bought your machine from Nobelton Farm Service. If that is the case I am VERY surprised that they were not able to put a little pressure on Deere for you.

As for the material the rod itself is made from, yes it is soft steel, in fact I also think it is just Superior shafting, however, I would urge you to use great caution if you have replaced it with hard chrome, if it bent before the hoe is obviously producing force in excess of that which the stock cylinder could withstand, that force will now be transferred to something else. A cylinder rod is a LOT cheaper than a hoe boom section.

See the other posting by Harvey on this same problem.

Best of luck. ....

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JD 48 back hoe bent cylinder shaft

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andywoj
Join Date: Jul 2003
Posts: 6 Caledon East, Ontario Canada
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2003-07-16          59609

HI Murf,

The relief pressures are to be checked next week to ensure that they are in spec. My opinion is that the shaft is to soft to handle the stresses at he angle of the ram when it is close to the end of its stroke, it is no longer a straight push.
....

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JD 48 back hoe bent cylinder shaft

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Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2003-07-16          59612

Andy, unless there is some physical interference from another part of the hoe how could it be possible for the cylinder to push in anything BUT a straight line.

Cylinders (IMHO) are most commonly bent as a result of one of two things, first from being the weakest link when forces exceed construction strength, or second, when they are inadvertantly forced against something like the wall of an excavation.

Best of luck. ....

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JD 48 back hoe bent cylinder shaft

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jeff r
Join Date: Jul 2003
Posts: 428 burton. michigan
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2003-07-17          59661

Murf is right. Cylinders get bent because they are the weakest link and that's why a maufacturer puts in a Relief valve so the cylinder doesn't try to do something it wasn't designed for at too high a pressure. ....

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JD 48 back hoe bent cylinder shaft

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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2003-07-18          59729

Digging with the stick is going to place a load on the bucket hydraulics. It may be that different bucket angles create different loads on the bucket when the stick or boom is operated. I guess I can see that there'd be greater load on the bucket shaft if the bucket was fully extended from the stick and then the stick was pulled in than when the bucket at an acute angle to the stick.

I'm not sure if that's the thinking here but I can see that some configurations in which it's possible to dig may exceed designed capacities.
....

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JD 48 back hoe bent cylinder shaft

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andywoj
Join Date: Jul 2003
Posts: 6 Caledon East, Ontario Canada
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2003-07-18          59735

Hi Murf,

When the ram is close to the end of the travel and the bucket stops traveling the shaft flexes enough that the cylinder keeps pushing until the shaft starts to bend. If the relief pressures are in spec. there is no way that the cylinder shaft should bend under its' own pressure. As to my complaint of leak down the piston in this cylinder does not use an "O" seal rather a loose fit single wiper made from some sort of plastic and it is not a close fit to the cylinder wall.
....

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JD 48 back hoe bent cylinder shaft

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Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2003-07-18          59742

Are you sure about the fit there Andy?

Unless it is a VERY close fit it won't hold pressure, i.e. won't do anything....

Best of luck. ....

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JD 48 back hoe bent cylinder shaft

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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster

2003-07-19          59793

Many cylinders have inner and outter seals, and the outter seal mostly wipes the shaft. ....

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