help needed

[greeniron]

have a old 550 ford backhoe with a slew problem
as in it does what it wants . i can make it slew around left or right but it will not hold itself in any position . is it possible for the control valve to be letting the oil to by-pass the relieve valves ( i`m thinking there would be two of them,1 for LH & 1 for RH swing ) or is there a brake inside the hoe rotory motor.

 

[daman]

what hoe you got 765? sounds like one possibility is a spool valve/check valve not holding.

 

[greeniron]

ok lets try a pic

 

[daman]

I still cant tell,it's a side shift,whats all over it? see a tag on the controls anyplace?

and what does slew mean,im not familiar with your term.

 

[davidd]

Like david slew the giant?

Slew = swing
:>

 

[Shaunrh]

Slew fault

Greeniron,
What I am thinking is your problem lies in the rotary motor.I think the vanes have been breaking up over time and finally the last one has broken allowing the oil to bypass so the boom does not stay in the one place.

Shaun

 

[greeniron]

daman , can`t find any tags and david is right on ------- slew = swing
Shaun , are you saying that there is only vanes in the swing motor ?
if you are right and the vanes have all broken , i would think that it would not slew/swing at all but it is swinging either way with loads - just not holding still in any one place

 

[daman]

Just checked my service manual(752 side shift hoe) a few possibility's are....


(boom travels w/control valve in neutral)
- internal leak
- relief valve stuck open
- check valve stuck open

other posibilitys.....

(erratic swing)
- defective pump
- aeration (oil)
- sticky spool valve
- orifice blocked
- bearings broken or wore

 

[greeniron]

daman , where is this check valve ?

 

[daman]

daman , where is this check valve ?

I'll post back let me check.....

 

[DGODGR]

This motor could have worn seals. It may work when you put enough flow to it (to overload the leak), but as soon as you close the valve it doesn't hold the fluid well enough to keep it "firm".

 

[greeniron]

dgodgr , possible but this thing is like a flag in the wind and i would think that if a seal / the seal or any seals had gone that it would not slew under load :beatsme

anyone got a parts page brake down of this slew motor so i can see whats inside of it possibly the control valve aswell or of the complete hyd system

 

[greeniron]

Ok , just an update to let you all know what the problem was . it was the seals in the slew motor . theres bugger all in there but they want $480 for the seal kit

 

[AussieChris]

Hey, thanks for posting the pics Greeniron. I've always wondered what those rotary motors looked like inside.

Yes, expensive but no more so than re-sealing two cylinders on twin ram slew.

Good luck with the re-build.

Chris.