My 680H backhoe works great and the cylinders don't leak. The boom, dipper, and bucket all work well as expected when digging. However, when I retract the boom to the full upright position (for transport), for the last 2-3 inches of travel before the boom cylinders bottom out, the boom gets bouncy as if it had air in the system. I don't think there can be any air in the system as there is no bounce and all movements are tight when the boom is lowered for digging. The bounciness only happens in the last 2-3 inches of travel. Hoses are good, and again, no leaks anywhere. What can be the cause for this? Is there something wrong inside my boom cylinders? there are two - one on each side of the boom Can this be caused by the control valve? - no leaks here either, and works perfectly under load when digging. The only thing that occurs to me that can cause this is that the bore of the cylinders are worn out in the particular upright position where the boom is bouncy - allowing hydraulic cylinder to bypass the piston - but I've never heard of this happening before in other applications, especially not in one where two cylinders actuate the boom. I wouldn't really care about this much except that this problem is preventing the boom from fully retracting so I can lock it upright on the swivel pin. When I need to transport it I usually pull it into position with something else (forklift, chain, etc.), and once it is locked, I can actuate the boom back towards me to release the pin locking mechanism. So it appears to retract fine once it is past the "bouncy" part of the travel. Your help is appreciated!
i got a similar on my bucket i found some gouges inside the cylinder at a certain spot and when the gland goes over it loses its seal /ie oil gets thru and at that moment and it get squirrley to operate .. just a guess not a expert i is
https://youtu.be/FeEg19cnriU
Thanks Shimmy1 - will try that this weekend! Hard to imagine you have to rough house this thing into place as the norm. I don't like being rough on equipment but it seems this is a case where nothing less will do. I wonder why they designed it this way?
After you get used to it you will be smooth as silk, the over center design gets the boom and dipper in closer to the tractor. As the cylinders are in the uppermost part of the travel they are close to the over center area and if you notice the cylinders will actually seep down a bit with the valve closed, this is caused by the cylinders creating enough pressure to open the secondaries till the cylinder pressure comes below secondary pressure .down movement stops.
Exactly what I was going to mention. Case is different and designed this way for better ground clearance and better weight distribution to the front. Case hoes are way less teter-tottery and bouncey than the rest of the backhoes out there because they are the only ones that offer an over-center bokm transport design. Practice the technique on the video shown and youll get good at it in no time. I personally prefer rpms to be around 1250-1500 when doing the boom transport lock.
Most people will either not get it over center, or SLAM it hard at first, but with just a little practice, you can make it into the lock with just a nice little "click" and away you go. You need enough rpm's to get the motion, but not too many. I like about 1200 myself, but everyone will find a sweet spot that works for them.
Overcenter wll be smoother and easier with the stabs down.