Bobcat 773 G AHC the lift and tilt (mostly the lift control) began to chatter/shake violently, the worst is when booming down. I have had it into the bobcat shop and have sunk over $6,000 in the last few months. Initially chasing an intermittent problem that turned out to be the controller, had that and the tilt actuator, spool seals and drive belt replaced the first time, got it home put no more than 1 hour on it and the lift actuator went. Back to Bobcat to have that replaced, got home and now the chattering. Bobcat sent out a tech today who checked a few things but couldn't figure what was wrong with it, the shop foreman says he's never heard of this before , wants me to bring it back into the shop, which is an hour and a half drive one way. Anybody out there with a similar problem I would love to hear the solution.!
Slip-stick is a thing. Don’t know if it’s your thing, but it’s a thing. Could be hyd oil related. Does the lift function only chatter when loaded? Or, all the time? Might be as simple as the emergency lower button being slightly depressed or the cable is hung up. Or, does the 773G even have one? 1.5 hours isn’t too bad. My record for furthest, expensive and most painful Bobcat service call was Dutch Harbor. https://blog.parker.com/site/usa/en...-rid-of-stick-slip-trouble-with-these-tips-us
It chatters whether loaded or not. Yes, it does have the emergency lower knob and my mechanic neighbor had the same concern, we played with that some but it had no effect. If I raise or drop it full tilt or go very slowly it will not chatter but normal working speed it gets pretty violent, like a jackhammer dropping in 6-8" bursts. The Tech couldn't believe it. Thanks for the info Coaldust.
A bent lift cylinder could be a culprit. Check them with a straight edge. Use the safety lock. Don’t get squashed.
Good idea, I will check them tomorrow. Thanks Coaldust.
Depending on the make of valve, an anti-chatter device (can't remember the name) might be a simple bolt on on the end of the valve spool. I had one installed on my skid steer under warranty. It has a Salami valve. It will still do it the odd time by very rarely and not nearly as bad. It was mostly when lifting, sometimes coming down too but did shake violently.
Welder Dave I believe that's one of the things the Tech was checking, I will ask him. Thanks! Coaldust, the lift cylinders are straight and true. When I had the arms in the full up position I used the emergency lower (knob that you twist and pull up) there was no chatter coming down. I ran it a bit this morning here's what I found (this is going full tilt on the joystick) on both the lift and tilt there is no chatter when going down, on both lift and tilt there is chatter going up. This only happens when I hold the joystick full over, like I said before normal operating there is always chatter and most notably on the downward lift function. Maybe this helps? Thanks gentlemen I appreciate all input!
Roger that. Tell me about the maintenance history and condition of the hydraulic oil. Maybe pull a sample and get an oil analysis report?
Anti chatter damper is what they called it.
It's a 2001 773G w/2500 hrs. I have owned it 10 yrs and put less than 1000 hrs on it. Before that my dad had it since 2003. We have used it for moving snow and moving logs around for our business. Took good care of it kept it clean and maintained on schedule. In winter kept in a heated shop. I changed the fluid/filter about 100 hrs ago. Now reading the invoice from the last shop visit, they changed the sight glass because of a leak and i see they put the same hydraulic oil back in. I should probably change it out again. What is the best way to get the oil analyzed, online kit, send it in or find a place locally ? Thanks again
Most Cat dealers do oil sampling.
What brand/weight is the hyd oil?
After some thought I have never changed out the hydraulic fluid only the filter. The last time I added to it I used HK aw-32. I went ahead and ordered a new filter, 2 case drain filters and a breather cap. My concern is if I change out all that and it turns out to be a major hydraulic system repair that is the problem it will need to be changed again?
What are the Bobcat oil specs. for your machine? It might not be straight hydraulic oil. Many skid steers actually use 10W-30 type tractor TDH fluid.
It calls for bobcat aw-32 hydro. Thanks
You should be OK then. Cat and others have an anti-chatter additive. It looks like it's more for sticky cylinders but I wonder if something like that could help in your Bobcat? Professional Grade Hydraulic Anti-Chatter Additive - Champion Brands
Thanks Dave, I will look into it!
I was hoping one of the Cat guys would chime in regarding the additive. The stuff Cat sells appears to the same or very similar. I don't think you'd need the whole container. I think Cat sells it in a 1 quart/Litre container.
If it was my job, I would change filters and cut them open for inspection. To verify if anything weird is going on. I would pull a hyd oil sample and wait for results. That will shed some light and help determine if we are dealing with a oil issue. There is a thread in the archives where I located the actual blender that packages and brands the Bobcat hyd oil. If curious. If the used oil is acceptable, I would consider the Cat additive. I’ve used it before to solve similar issues with 400 series Cat BHL’s and other compact machines. If the SOS results are bad, I would change the oil and see what happens. Pay particular attention to the Bobcat ISO 4406 cleanliness code requirements. Which, I don’t remember off the top of my head. Because, my brain is locked in truck mode today instead of dirt mode. I have access to the new Chevron ISO clean packaged products and I’m excited about being able to source and install clean hyd oil that doesn’t need pre-filtering. I think that’s awesome. Because hydraulics are expensive and “clean” oil is critical, contamination control, blah, blah, yada, yada. Send me a Purchase Order and a credit card number and I’ll fix that ol’e Bobcat up for you soon as I finish my South Carolina job. Still can’t believe my client sent me to the land of Chick-Fil-A to do this. The travel cost is enormous. Like $3,500 just in air fair. Guess I’ve spent more on chartered helicopters before when I worked for wages, but not for my business clients.
One of the lift cylinders had been leaking from the top for some time so I pulled that and ordered a seal kit, I am waiting for that and the filters to show up before I pull the old filters for inspection. My neighbor/mechanic said the fluid looked fine and didn't seemed concerned about the burned transmission fluid like smell to it. I am replacing it anyway. I haven't been to town yet to have it analyzed. Is there anything in particular that I should look for in the filters?
Take the filter element and cut out 5-6 pleats. Take it to a clean vice. Give it a squeeze. Now, you have a dry sample of element. Pull the accordion apart and read it like a book. aluminum? Iron? -does a magnet stick? Contamination- rubber, dirt, gravel, dead elephants Take a picture and show us what’s up. Don’t contaminate the filter element sawing the can off. A can opener works best.
Thanks Coaldust!. I'll do that tomorrow, Appreciate.
Going back to your first post, you mentioned replacing the controller, would that be the joystick controller or the main controller (computer)?
Going back to your first post, you mentioned replacing the controller, would that be the joystick controller or the main controller (computer)?
They replaced the main controller.
There was nothing metallic and I couldn't see any aluminum, I did my best to get close-ups of the soft black fragments. Hope this helps. Thanks again guys!
The filter had 38 hours on it
Thanks for the pictures. Looks like particles from the inner-most tube of a hydraulic hose. Maybe junk left over from someone building a new hose assembly? Have you replaced any hoses recently? I’ll be curious what the seals in the leaking lift cylinder look like.
Hey Coaldust, there hasn't been work performed on a hose or any hose replaced on the machine in the last 10 years, to my memory anyway. The wiper seal is obviously bad and there is a small inclusion or cavity on the orange seal pictured. I appreciate your help with this!
Do you run any hydraulic attachments with this unit?
I bought a used woodsplitter a few years ago that I plugged in, it immediately blew the cylinder which I found out was not rated for the unit. I replaced the cylinder, ran it for an hour maybe before a hose began to leak. The unit is homemade and I don't doubt it had contaminated fluid. That is the only attachment since I have owned it. (10 yrs) I changed the case drain filters out today
Well, I changed out the fluid, filter, the 2 casedrain filters and breather cap. I also put new seals in the leaking lift arm cylinder. The problem persists! Any thoughts coaldust? willie59? welder dave?
Hmmm. I have a long trip ahead of me today. I’ll ponder this riddle along the way and give you a shout back.
Alrighty. So, I chatted with my Bobcat dealer principle, guru, Buddy of mine and he recommended isolating one loader cylinder at a time. See if the chatter only happens with one cylinder or another. That will help isolate the problem: control valve vs cylinders.
We had brand new 400 series chatter it was a seal in pump in warranty it was 20 plus years ago I know if the inlet on mine was leaking it blew oil out the tank might check the seals on the pump
Thanks for the input guys. I got busy and put this project aside for awhile. I have been using the bobcat, I had added/replaced a gallon of Lucas hydraulic booster to the system and I am not sure if it helped, there is less chatter but I suspect I just got better at manipulating the controls. I won't be bringing it back to the dealership for repairs, I will have time this winter. Thanks Coaldust ! Great idea, makes sense. Thanks Tripowerpaving I really appreciate all input.
The fact that it lowers smoothly using the manual bleed valve makes me think it’s not a cylinder binding or chattering. Can you see the movement of the pilot actuators on the valve when you move the lever in the cab to see If they are moving smoothly or chattering. May be a bad ground or connection in the electrical side.
Did you ever find the solution? Mine is doing the exact same thing on the exact same model and year. I’ve done everything you’ve already done in this thread. Only thing that’s been newly recommended to me is adding a capacitor harness jumper in line. Any info would help, thanks!
Did you ever find the solution? Mine is doing the exact same thing on the exact same model and year. I’ve done everything you’ve already done in this thread. Only thing that’s been newly recommended to me is adding a capacitor harness jumper in line. Any info would help, thanks!
The fact that you’re both in Minnesota and this is an old post, would make me suspect as to the OP still being said owner of possessed machine and wondering if it you! Lol
Haha nope I just got it about a month ago so not the same! Wish I could get an answer on it though, it’s frustrating ha
I bet it’s frustrating but either way, the original OP may not have the machine, YOU may have it now!