Need Help with Hydraulics Jerking Motion on a JD 310c Backhoe/loader

Hi Everyone, I need help with the hydraulics Jerking motion. I feel i need to tell you a huge part of its history first. The Loader, Hoe, and Stabilizers all give a jerking motion when lifting them under load, mainly when cold, and as it warms up it very slowly goes away, on some very cold days if it does go away it can take the entire day of operating it as the jerking motion is more tolerable, but it will never go away totally. The hard jerking motion is almost gone when its in the middle of the Summer and its in the high 90's is when it feels like its gone. But with the colder it is the harder I get the jerking motion, especially the loader, when I pull up on the loader no matter if I go slow pulling the lever back, or make the action of raising the loader faster the jerking action is all the same when raising the loader going up, it's so violent that it's shaking the machine so hard I feel like nuts and bolts are going to fall off soon, and I bounce up and down in the seat so bad I can't hold the video recorder steady enough to record what its doing because I'm violently shaking all over the place, this is how bad this problem has become now. Its hard for me to say because I've used it all the time when it was hot out, but I say it has been this way pretty much since I got it, it was in the high 90's when I looked to buy it, I never really noticed it because I didn't really work it hard, I just checked things that they worked. But over the 4 years its been progressively gotten worse. It's all an intermittent problem and nothing about it is consistent, when I went to record this on video the other day the loader almost made it all the way up with hardly any jerking. then like I mentioned there is no consistency to this problem and for the rest of the time I get such a violent jerking of the loader going up its shaking the heck out of everything, and at times it gives me only one or two very hard jerking motions while raising the loader, empty or full don't matter. The same goes for the stabilizers and all of the hydraulics for the rear hoe arm, under load only, full or empty loads don't matter. I don't believe its the main hydraulic pump because I get this problem even when I pull the loader arm slowly, so if the loader valves were starving for fluid from a weak pump I would think my logic would be prudent. But I don't know, can I be wrong? I'm going to post videos soon. Now just to mention the Main Hyd. Pump on my John Deere 310c shows the most forward section of the hyd pump is for the power steering, and thats all working great, nothing wrong with the steering, now if the front and rear sections of the main pump share I don't know? but the rear section is for the loader/backhoe/stabilizers, and each one does this jerking motion under any kind of a load only, when letting the arms are going down its all smooth action, not even a hiccup when lowering the loader. I did all the obvious already, changed hyd. filter, check the screen in the hyd. tank, followed the hydraulic feed line coming off the main hyd pump to see that it goes to the loader valve first, so I pulled out the Stabilizer Relief Valve above where the hyd feed line goes in and it looked good, so I rebuilt it anyway and made sure it all worked perfect. Then I took out the other valve on the loader assay. that is called the Circuit Relief Valve, it also looked good, so I polished it up and put it back in, but this particular valve when installed new needs to be calibrated to I believe 2500 PSI ?? well anyway I put it back together the same way I took it apart and with having cleaned and inspected both of these valves didn't make a difference. I do have one hypothesis that makes me think perhaps something is being overlooked with the loader valve assembly. I asked the guy who sold it to me why does the loader handle have a turbo button on top when its not a turbo, or even shows signs in the engine compartment where there use to be a turbo, unless I'm mistaken and you won't see any signs in the engine compartment if there ever was a turbo and it was removed, so the guy said "totally ignore that button on the loader handle" and acted like the case of discussion was closed to mention it any further. So I suspect that, being all this guy does is buy machines at the auction, fixes them, paints them, his whole yard was full of heavy equipment, this guy was big time into fixing and selling, so I suspect who knows if he most likely put one good backhoe together out of Three salvage units and I bought it, this is why I'm thinking that the loader valve might not have been what my machine came with and its never been properly calibrated having replaced the one that was in my machine. but then if it was not adjusted correctly would it give me this problem? There is one more thing in the loader valve I need to check, it looks to be a solenoid, not sure what it does and why. Sorry guys for the long winded message, I figured it could help, because I'm totally lost here and can only hope someone knows about this and where I can look next. Thanks, Joe