Erradic Lift Cylinder Movement

tbyrd1960 · Mar 7, 2011

I have a 1965 Ford 4400 TLB. The backhoe on my 4400 is a model 753. All works well except the lift cylinder which is very erradic when I operate the lever to lift it. I try to feather it slowly, but if the bucket is empty, it is very very difficult to accomplish a smooth lift. What should I look for? It was like this when I got the tractor. The Vickers vane pump was worn out when I got it so I replaced it along with many new lines, but as I said, the movement of the lift cylinder was erradic before I did anything. I am a decent mechanic, but not a student of hydraulics; any help to point me in the right direction will be appreciated.

J_J · Mar 7, 2011

Did you try swapping the lift cyl hose to another spool to check things out?

The nut on back of the lift cyl piston might be loose.

wdchyd · Mar 8, 2011

You may want to check for bent hyd rod or binding in cyl barrel (dented)....or frozen/rusted pivot pins.....or just an air pocket in the cyl....

tbyrd1960 · Mar 11, 2011

Switching the lift cylinder hose to another spool is a good idea. The more I study it, the more I think that particular spool might have a small problem. Could be the spool spring or oring. I am not much for fixing something that still works. I have heard removing a spool can result in something different than what I would hope to find. I noticed that when I first start the machine, the lift cylinder movement is not bad, but after running it for a while the lift cylinder function becomes jerky while other movements are OK. I have read that worn spools do this because as the hydraulic oil warms it becomes thinner which causes the action through the spool to be different. Wish I could know for sure before taking anything apart.

J_J · Mar 11, 2011

I would take things apart until you verify that a particular spool is bad. Just switch the hoses to verify. Perhaps do a pressure check on that spool, and compare to the others.

wdchyd · Mar 11, 2011

tbyrd1960 said:
I noticed that when I first start the machine, the lift cylinder movement is not bad, but after running it for a while the lift cylinder function becomes jerky while other movements are OK. I have read that worn spools do this because as the hydraulic oil warms it becomes thinner .

Don't know where you read that, with your description it may be a pump aeration/cavatation problem, Relief valve..??.. Maybe..??.......not spools..