B7500 3 point hitch hydraulic problem

[dannyk]

I need some help with a 3ph hydraulic problem. I purchased my B7500 last year and it performed flawlessly. I use the tractor only for mowing with a 60" mid mount mower and, with the mmm removed, with a 48" brush hog. I keep the "implement lowering limit" adjusted so my brush hog remains level. Those of you having position control on your tractors may not be familiar with this limiter. It is a simple sliding stop on a rod beneath the right rear of the tractor seat. It works well in place of position control for me since I only have one rear implement and don’t need to change the limiter position once it is set. (It’s a pain in the rear to change it.) It prevents the rear 3 point arms from dropping too low so that the hog would scalp.

The first problem I noticed was when I started the tractor in late May after winter storage. There were all sorts of noises, banging and other undesirables, which I finally realized were related to the hydraulic lift control lever not being in the fully neutral position (It was close, but not fully centered). I had tried to put it in neutral before starting the tractor, but it would not shift fully into neutral, and I didn’t want to force it. OK, problem solved, I’m thinking. Now when I start the tractor, if the lever won’t go fully into neutral, I simply put it into neutral immediately after starting the engine.

Next thing I notice is early this August when I am removing the mmm. The pin that holds the left anti-scalping wheel on the mower (the wheel that turns 90 degrees when sliding the mower out) is bent so badly I have to drill it out. I’m a little confused about how that could have happened, but I proceed with brush hogging my nine acres. I had no problems with the hydraulics, but I did notice that once when I stopped the tractor for lunch and forgot to close the 3-point lowering speed knob, the front of the brush hog did lower past the limit until it was resting on the ground. I had no problems when I resumed mowing.

This weekend I remounted the mmm after removing the brush hog. Now I find that when I lower the mower to the ground I hear grinding and/or squealing noises that I can alleviate by working the hydraulic lever back and forth a bit. But I also notice that the three point arms are not in float. That is to say, when the mmm in on the ground, the three point arms are locked into position and will not move. I may be crazy, but I was sure that before when using the mmm that the 3 point arms could easily by lifted by hand. That is they "float" upwards even though their downward travel was limited to horizontal by the so-called implement-lowering limit.

I am obviously going to call the dealer Monday, but I sure would appreciate any advice/knowledge about the 3ph hydraulic system that may relate to my problem. For example, if the rear 3ph arms are not in float, does that mean my mmm is also not floating on the ground, and could that be the cause of the bent anti-scalping wheel pin? At this point I will not be using the tractor until I get the 3ph hydraulic system figured out and working properly. I would really appreciate hearing from anyone who can help. Thanks!

 

[snowman]

Can't help you too much on the technical workings of the 3 pt, but I can tell you that the 3 pt and mmm are the one and the same, so that when the 3 pt floats, so does the mmm hardware.

When in float, you should be able to raise the 3 pt arms easily.

I have the same tractor as you.

The 3 pt and mmm hardware is pretty tough. My check chains have been bent, I bent up the mmm arm hookups when I lost a pin, and the mmm itself has been beaten up pretty good. All of it still works fine though.

I've never had noises due to the 3 pt lever not being in neutral. Have you ever changed the hyrdraulic oil? Have you
checked to make sure that it's full?

Good luck

 

[dannyk]

Thanks Snowman. The hydraulic fluid is brand new and full. Let me ask a more general question:

When the mid mower is on the ground and the hydraulic lever is in center position, should a person be able to raise the three point arms by hand easily?

Thanks!

 

[snowman]

I've never tried it, but I think that it would be much harder, because you would be trying to lift the weight of the mower.

Depends too on if you let the 3 pt arms drift all the way to the bottom when you let the mmm down.

What I usually do when I drop the mower is then push the 3 pt lever just enough to raise the 3 pt arms up without moving the mmm off of the ground so that the arms are not too close to the ground (because I back up alot when mowing and will ram the arms into something if they are too low)

 

[GregJ]

Danny,
The center position is basically the lock position. The forward (down) position is the "float" position.

Greg

 

[dannyk]

Thanks Greg,

That may explain some of my confusion about the floating 3 point arms. I'll see if they float when the lever is in the forward postion. I'm still concerned about the squealing and grinding though. The manual and my mechanic says there is a hydraulic mechanism adjustment that may need to be performed. The mmm is removed and the lift arms are raised. Then there is supposed to be 5-15mm clearance somewhere. Something about near the rockshaft. I don't know what a rockshaft is yet, but I'm going to try to find out more about this adjustment. Has anyone done this?

Thanks again, Danny.

 

[don716]

Dannyk,
I own a B7500 too and I have'nt had any problems so far.It has 62hrs on it and performs well. My question is what size bush hog do you have and how well does it work for you? I run a 4 ft on mine but would like to have a 5 ft but I don't know how well the 7500 will handle it.
Donny /forums/images/graemlins/smile.gif

 

[dannyk]

Donny,

I use a 48" hog. I have been cutting very tall thick grass and light brush. To get a decent cut, I go very slowly although there is no apparent strain on the engine. My reading suggests that a 5-foot hog would not be appropriate for the B7500, but I have no experience in this regard.

Good luck!

 

[dannyk]

Having spent some time talking with the mechanic and working with my tractor, I am going to try to answer some of my own questions. Maybe this information will be of use to other owners of the B7500. I do not know if this device is present on any other Kubota tractors. I am new to modern hydraulic CUTs, so if more experienced B7500 owners have comments or think I am in error, I would certainly appreciate hearing from them.

The bottom line is that I THINK that most of my issues relate to use of the "implement lowering limit" which is located on the the "feedback rod" beneath the right side of the tractor seat. Kubota tucks this thing out of the way, perhaps hoping that no one will try to use it. It consists of a small clamp, a couple of nuts, and a set screw. My unit was delivered with the nuts facing upwards, which made it nearly impossible to get a wrench on it. I removed the entire feedback rod to move the limiter, and now I have the nuts facing to the right. (By turning the limiter 90 degrees, there is room to move a wrench in the vertical direction, whereas previously there was no room to work a wrench in the horizontal direction.)

The good news is that the limiter works as advertised in the manual. It replaces the need for check chains or for the operator to constantly monitor the position of the front of the bush hog so that it does not scalp.

Here is what the B7500 manual does not tell you:

Use of the limiter can make the hydraulic lift lever stick after the tractor is shut down so that the lever cannot be centered or moved freely before restarting. I do not understand the theory behind this, but based on some of the noises I have heard, I suspect this mechanism has the potential to damage the tractor hydraulics. I hope I have not damaged mine, but I don’t know. I’ll probably find out as soon as the warranty period is over!

To prevent the lever sticking, I would always advise resting the rear implement on a support so that the implement does not fall below the level set by the limiter when the tractor is not running. I have not had problems with the hydraulics when following this procedure.

Second, I would never leave the limiter in place when using a different implement or when storing the tractor. I originally thought I could just set the thing and leave it. Bad idea, since it will also limit the downward travel of the mmm. And, as I stated above, it seems to result in hydraulic problems when the tractor is restarted.

The limiter is not a terrible idea. It’s simple and it works. But Kubota’s design makes it difficult to adjust, and the B7500 manual does not provide nearly enough information about its use. Perhaps that’s why it has been replaced in the B7510. I hope that this is all that I will have to say on the subject, but if I get more useful information, I will post it in this thread.

Danny

 

[snowman]

Danny;

I've read your posts a couple of times and still am not clear on what the "implement lowering device" does or is designed to do.

If it's as hard to get to and adjust as you describe, then, as you say, it might be that it's something that Kubota does not really want people to use, which doesn't make sense if it really is a device to use with 3 pt implements.

I don't think that I have this on mine, but I'm nt home now, so I can't look. I have a PDF file that I downloaded back in 2001 that shows all of the tractor part numbers and exploding diagrams, and I couldn't find what you describe. I bought my B7500HST in February 2001, so it's possible that Kubota added something after my was built.

I do have that knob that changes the rate of lowering of the 3 pt. I have also read other people's post describing the adding of position control and the need to add it to the B7500 if you want it, which leads me to believe that the rod that you adjusted maybe should not have been.

I would think that you could accomplish what you're trying to do (keep the 3pt at a set level) by (1) getting it to the desired level and (2) turning that knob under the front seat so that the 3 pt doesn't move from your desired setting. Maybe if you put that rod back the way it was (nuts up) and do this, that would cure your problems?

What did the Kubota mechanic say about changing this rod? Did he say it was okay to do?

Just curious about this. I'll have to take a look tonight to see if I have that.