Altec Lift

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77 Ford
1010 crawler
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Joined: Tue Nov 22, 2011 7:52 pm
Location: Missouri

Altec Lift

Post by 77 Ford » Mon Aug 21, 2017 9:25 am

I've got a AA755L altec lift that blows the hydraulic return filter seal when it's in out rigger mode. For those who don't know there is a selector valve that you push/pull that either drives the outriggers or allows fluid to control the main boom assembly. Twice now while in out rigger mode it's blow the seal on the return filter. I don't really see much in the circuit that could cause this. There is not a main relief valve its a variable displacement pump, so I'm wondering if the pump is creating too much pressure for the out rigger circuit. Does anyone have any suggestions or know a good altec guy I could call to discuss?

Thanks!
JD- 450C track loader
Serial #208336T

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pop pop
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Re: Altec Lift

Post by pop pop » Mon Aug 21, 2017 6:38 pm

i dont know the machine, but you have described to me what seems to be a flow problem,, or overflow.
you might try adding a restrictor to that control valve(s) only.,, active on cyl. return only.
maybe your oil is thick, probably not but maybe the filter is plugging. or wrong filter??
might already be flow controls located in the system.
corroded? old o-rings parts stuck in there?
the valve itself may be adjustable.
maybe the RPM has to be at idle for outrigger return..
it can be a can of worms but its all logic.

help us by telling valvebody spec.s
hose sizes, or link us to an exact layout.
440icd/602,,, 440icd/831/ripper, misc. 440 parts

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Lavoy
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Re: Altec Lift

Post by Lavoy » Mon Aug 21, 2017 7:04 pm

Would seem to be a down stream from the filter restriction of some sort. Filter should flow all the pump can put out and then some.
Lavoy
Parts and restoration for antique and late model John Deere crawlers.
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77 Ford
1010 crawler
1010 crawler
Posts: 294
Joined: Tue Nov 22, 2011 7:52 pm
Location: Missouri

Re: Altec Lift

Post by 77 Ford » Fri Aug 25, 2017 7:14 am

I actually found a technical support number for Altec that gives free advice. They claim it's an issue with the variable speed pump being spooled up to move the out riggers when you close the valve the pump is moving so much fluid it over whelms the filter and creates pressure which pops it. They say it's a known issue and the fix is to replace the stock filter/base with a filter/base that can flow 50 gpms and hold 150 psi. I can not find exactly what the stock filter would hold but I think it was 15 - 18 gpms (standard screw on hydraulic filter). The new filter/base is 100 bucks so I'm going to give that a try.

It's hard to imagine it's survived since 2006 without the fix but I got the impression if you feathered the valves carefully so it didn't create the surge you might be able to make it work. We'll see what happens, thank you for the suggestions if this doesn't work I'll move on to some of your ideas.

Phillip
JD- 450C track loader
Serial #208336T

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