7753 lift lock valve

[truckdiagnostics]

I have a 7753 had it for ever do all my own work on it and I am the one to use it, so i know it rather well.
My questions is this, do the lift lock vales fail more often then one would want?
It lifts slow, tilt is fine. The issue started all of a sudden. does not appear to labor when it lifts slow. It is not the electric solenoid valve other wise it would have issues with the tilt. The linkage could be a little tighter.
Thing is maybe 5 years ago I replaced it, that is what is making me question things.
I also don't remember just what I did looking at the parts book


it is item 37
thank you

 

[truckdiagnostics]

I am thinking the cap on the left is item 4.
Then looking at the hydraulic schematic item 37 lift lock valve, item 4 is right above the x. X is piolet pressure? near as I can figure every time this thing starts up and runs that valve item 4 moves.

So does this mean it will wear out?
If it walks like a duck and talks like a duck it is a duck. it just was not that long ago I replaced it and I can't come up with anything else it can be..... or this makes the most sense.
now when I say lifts slow, it will not lift at all until you rev it up and the engine does not seam to labor.

All that, near as I can figure point too...... number 4, in the lift lock valve.(item 37)
Now how do i get it out?
i thinking, I am going to cut a hole so I can get at it.

 

[Xfaxman]

The service manual should have a pressure test procedure that would tell you a lot about your problem.

 

[truckdiagnostics]

I went back and looked incase i missed anything. this appears to be the extent of there troubleshooting. It is in a three ring binder so i could be missing some pages.
Thanks for the suggesting.
i did think about testing. I have yet to find a test port....... I can rule ot a lot of them with educated guesses.
the linkage is a little sloppy. I however don't think it is worn enough. Getting to the one that is a little sloppy is a bit of an issue.
And the thing is, I haven't figured out a way you can manually stroke that valve and do it safely.
could be the check valve in the lift lock valve.
When i throw parts at it I am going to replace that also.
The verdict is not in on the manual valve-I pull the knob to bring it down on the safety props and it didn't do anything?
i thought you pull that and you can get the lift arm to go down. That might be a clue? Ugh!

 

[truckdiagnostics]

Wrong image and for some reason it rotated it.

 

[SSdoxie]

If the lock valve is not opening fully, causing enough restriction to slow fluid flow you should be able to hear additional hydraulic whine and/or engine rpm loss when raising lift arm only as compared to operating bucket tilt.
If the lock valve was by-passing oil it would be to tank because the the rod end circuit does not pass through this valve, and if it was by-passing to tank then lift arm would steadily drift down when pedal in neutral.
Reference the troubleshooting chart: #4 problem (linkage adjustment) is the only possible cause listed that would pertain to one function only. All the others would show similar issue in both lift and tilt.

Address the loose sloppy linkage before throwing other parts at it.

 

[truckdiagnostics]

thanks.... got the slop out of the linkage when I get the alternator back in I will test it.
It has hand controls don't see how that would make a difference.
It does drift down, tilt drifts also and I have rebuilt the tilt cylinder thinking that was it.
There is however something I just noticed.

When I take the lift handle and tip it all the way down or in, there appears to be a stop, then I can push the handle further have to force it not rear hard, never noticed it until I started playing with the linkage. Could that be putting it into float? or is there something going on in the valve? you can hear and feel it jump like it is going over a detent or something. You would have thought I would have noticed this before?