I tried a search for this info with much luck. If anyone could help me, it sure would save my kidneys. When I lower - not raise - the loader arms on our 963G - the chatter (chatter is an understatement - I practically see double) is intense. I have changed 2 hydraulic filters and the hydraulic tank breather cap. :Banghead Can anyone figure this out? Someone mentioned a regenerative valve. Any info on that? Thanks
Does it chatter when you go into a pile and really work it. Ours would do that, and we had bobcat come out and everything they could never figure out the problem. We tried everything then we decided to change the drive belt, and that was the problem it never did it again. Good luck.
We did just replace the big hydraulic pump belt. Is that the one you are talking about? Unfortunately the problem remains. It does seem to worsen the more I use it but then again, maybe it's the cumulative effect! Today a mechanic suggested that I look to see if the arms are still aligned properly. The thinking being that they might not come down evenly. I will take any help and suggestions. Thanks!
You have a strange problem pconnelly, one I haven't seen before. Does the 963G use manual pedal links to control the main control valve? I assume it does. When you drop the bucket to the ground, will it lift the front of the machine using loader arms? Does lowering the loader arms chatter no matter if the bucket is loaded or empty?
I honestly don't know if the foot pedal controls work. I run everything off the joysticks - forward and back = forward and reverse, left side to side = the loader arms, up and down, right side to side = bucket, fill and dump. The hydraulic is very powerful. It can easily lift the front of the machine. If I drop the arms, bang, full speed there is no chatter, and if I go very slowly, no chatter, but if I lower the arms at a normal working speed, I I I I gggggggettttttt the heavy shshshshakkkkking, see what I mmmmmmean! Thanks BTW, your description of overhauling the 773 was fantastic!
I just had a feeling you had a joystick controlled machine. I don't have any experience with that type of controls on Bobcats, but I'd be willing to bet my paycheck that your problem is in the electronic controls. Could be a joystick, could be a servo coil at the control valve, could be the ECU that controls everything, could be the joystick just needs calibrated. I have no idea how to do any of these actions on these machines, but if you have a competent Bobcat dealer in your area they should be able to fix this problem. For that matter, why don't you switch to foot pedal control and see if it operates different. The joysticks and foot pedals are independent of each other, they send inputs to the ECU, then the ECU sends input to the valve servos. If it works proper using foot pedals, chances are you've narrowed your problem to the joystick or the wiring harness from joystick to ECU.
Being Sunday and all, even though tooling with a bobcat or the like should be considered entertainment or relaxation, but I will wait till tomorrow to try to switch over the controls from the joysticks to the foot pedals, but I have another question. Someone said I should check how well greased it is. I m fairly diligent about greasing the machine but with long days of moving snow, could I have let the lubrication get that bad? Thanks
Well, anything is possible. But with the exaggerated bouncing you're describing sounds like a bit more than a sticky pin.
873G Hydraulic pump problem . This may not be the proper forum for my question but if there is any information available I would greatly appreciate the assistance. I have a 2001 Bobcat 873G with 1400 hours on the machine. About 8 months ago the hydraulic gear pump developed a minor leak which appeared to be coming out from around one of the 4 case bolts. I put a wrench on the bolts to make sure they were tight. They were. The leak was minor so I continued using the machine. After doing a pool demo with a rock hammer attachment the leak became much worse. It was leaking about one quart of fluid per hour. I had assumed the seals in the pump had gone bad so I ordered a rebuild kit for the pump. While waiting for the kit to arrive, the high pressure side of the pump cracked from end to end and dumped about 3 gallons of fluid everywhere in a matter of seconds. I removed the pump and disassembled it. All internal componants are in excellent condition. I am wondering if the aluminum case is prone to breaking in this manner or should I be looking for a more severe underlying problem? I have a new pump but I am concerned that installing it may be a mistake if a deeper issue exists. All hydraulic fluid is changed every 500 hours. Filter is changed every 150 hours. Machine is well maintained. Please help if you can.
I have experienced cracked work equipment pumps on a number of Bobcat skid models. Haven't ran across one for some time now, but it's not an uncommon problem on Bobcats. Never have determined if it's a particular operation that causes the failure, or whether it's simply faulty pump design. I've replaced the cracked pumps on machines with a new replacement pump and had no more issues with the machine or pump. :beatsme
Pconnelly, from what you have said it seems that if it was a sticking loader pin it would be getting a vibration both lifting and lowering. From what it sounds like you might have a sticking valve, broken spring, or leaking seal in the lowering circuit. One way of testing would be to disconnect the pressure line from the top side of the cylinder and plum that back into the reservoir. Therefore we can still raise and lower the linkage arms, the hydraulic flow to force the boom down will be rerouted into the reservoir. Now if it still shudders that means one of two things, either the pins are sticking or you have problems with the raising circuit. Now if it operates correctly that means, it is a hydraulic problem with the lowering circuit. Given that there is a much higher flow when the boom is on its way down, the hydraulic flow might be restricted in a sticking return valve, or a filter. What may be happening is that on its way down the system may not be able to cope with the high flow, the hydraulic back-pressure will rise to a point where the relief will kick in then drop sufficiently to allow more oil to routed to drop the cylinder. Now a way to test this theory is to plum in a pressure gauge and look for spikes in the oil pressure. From this high frequency vibration there should be some. Now if the filters are all new and no hoses have been pinched or collapsed, then i think your best bet would be to check out every valve in the boom raise and lower circuit. hope this helps best of luck Alex
pconnelly, did you get your problem figured out? I am having the same issue with my 773 G turbo! Thhh-aaannk-sss!!