Mini excavator final drive question

[RPF207]

One step forward, two steps back……

in my previous post I explained my solution to my high speed travel on my 2000 hitachi ex35u not working. Well, the high speed travel engages now but only on one side and it gets stuck in high speed until I shut the machine off.

the side that doesn’t go into high speed…… I’ve had the final drive on that side apart to fix something else on it that’s not related to this problem. When I had that side apart I noticed the “piston” that pushes on the swash plate to engage in high speed travel could not be pulled all the way out by hand. I’m pretty you could get it most of the way out but it would get hung up. It took 200 psi of air to pop the piston out, and when I assembled it I put the piston in the freezer to shrink it.

anyways, right now that piston is the only thing I can think that could be causing my issue. But it did move most of the way so I really don’t know.

anyone know why one side would get stuck in high speed and the other side not go into high speed? Everything looked excellent when I had it apart and the machine moves fine in low speed travel

 

[uffex]

Good day
I suggest getting the fluid checked for contamination. Some machines drain the high speed valve via an orifice this may become obstructed.
Kind regards
Uffex

 

[RPF207]

Good day
I suggest getting the fluid checked for contamination. Some machines drain the high speed valve via an orifice this may become obstructed.
Kind regards
Uffex

i really appreciate the help. The orifice you are talking about is located within the final drive?

Contamination build up is possible I suppose since the high speed travel hadn’t worked in years, maybe 10 or more.

 

[uffex]

Good day RP
We need a hydraulic schematic to point you in the right direction, we do not have one on file ,if you have a service manual it should be included - post a copy we can make some suggestions.
Kind regards
Uffex

 

[RPF207]

I have a pdf of a 539 page “technical manual”. It is too large to upload, I could try to email it to you or try to look later today for the pages related to the issue. I don’t remember a “service manual” in pdf or hard copy being available when I looked.

thank you

 

[uffex]

Good day RP
Can you post what information you have onto a Gdrive (No file size restriction) it is free goes with a Google Email address, post me the link and access code, then we can make some troubleshooting information for you.
Kind regards
Uffex

 

[uffex]

Good day RP
Update a contact has posted a schematic, so please be patient, we will come back with some suggestions.
Kind regards

 

[RPF207]

Great, I really appreciate the efforts.

I just happened to stop by a hydraulic shop to deliver a malfunctioning stick saw and asked his opinion on my situation. I told him about the piston for the swash plate and how I needed to apply a lot of air to the port to push it out. He said he doesn’t believe it should’ve done that and it should’ve come out by hand. Again, it did move in and out by hand some but wasn’t able to actually pull it all the way out to remove it. He also doesn’t work on excavators often so he said it was just his opinion.

 

[uffex]

Good day RD
Please see attached, normally the valve should move freely
Kind regards
Uffex

 

[RPF207]

So the diagram is telling me that there are external Allen plugs that have restricting Orifices Behind them? Is this something where I can remove the Allen plug and clean out the parts inside? I am familiar with the plugs being there on the outside of the motor.

hopefully removing the motor and inspecting the swash plate piston is a last resort, it moved to what I would say is 90% plus of its full travel but I just couldn’t pull it all the way out until pressure was applied.

this has been a HUGE amount of help.

 

[uffex]

Good day RP
Yes remove the plugs behind you should have an orifice most makers screw them in with an Allen key but there are variants, any obstruction to wither will prevent the high speed becoming engaged. You could use a jet cleaner take a good note what comes out from behind the plug you may well find the cause.
Kind regards
Uffex

 

[RPF207]

Ok, I took a look at the motor and the plugs. I will need to remove to motor to be able to do the job properly on a bench. I also need to buy some plugs for the 4 hydraulic lines going to the motor. Should have it apart by the weekend, time is on short supply.

cant thank you enough for the help, I will will let you know what I find

 

[RPF207]

Pulled the motor. Removed two sets of plugs. One for the high speed valve and one for the brake I assume. Removed the few parts inside, inspected the tiny ports, Both were VERY clean. Didn’t see anything I could do to make it better, so I put It back together. Pulled the mini excavator outta the shop, and drove it a bit, finally engaged high speed travel and same symptoms, one side engages, one side doesn’t, and it remains that way until I shut the machine off to get full low speed back. Idk, maybe it’s air trapped in there I’m not sure, might use it for a bit to see what happens. Finally got the cab back on it for the first time in a year after taking it all apart. Next up, boring out the quick coupler/extension to accept replaceable bushings. I say extension because it’s a longer than normal quick coupler to suit the length of the main pin thumb. It was built with solid steel bushings that have play.

any more thoughts on the high speed situation are more than welcome! Thank you

 

[heymccall]

I'd start by removing both travel shift lines from the motors back to the tee at the rotary union and verify that fluid can pass easily through both. And, that there also isn't an obstruction in the tee itself.

On one of my Takeuchi TB180FR machines, one of the speed shift hoses was installed in a manner in which the hose was crushed when the center guard cover was installed. On that one, one side was extremely delayed both in upshift and downshift.

 

[RPF207]

Thanks, I’ll look into it. I did notice when high speed is engaged, and I push the lever for the travel on the track that is “stuck” in low speed, I hear a noise that sounds like restricted hydraulic flow. Happens in either direction on that side.

I guess it could also sound similar to air traveling through the line. I haven’t run it enough to see if the noise goes away after a while. I do know after I’ve had the hydraulic track motor off and put it back on, the motor seems to need to purge some air for a few days…… meaning every once in a while for a week you push the lever to move, nothing will happen. Lift that side off the ground and push the lever again and it moves fine for a while until the next day. Stops doing that after a bit

 

[uffex]

Good day
I suggest you make a check that the lame side is getting power and actually turning the track and not being carried by the good side.
Kind regards
Uffex

 

[RPF207]

It can turn itself independently if that’s what you mean? And turn the machine by itself. I also resealed the center joint because the lame side was a bit slow traveling Lon distance l, I noticed it would track to that side over time. Resealing the center joint didn’t change anything. But the two motors are of different manufacturers it seems and one of the lines, a small one goes the a different location on the motor I believe has been replaced which would be the side that is acting fine. The two large and one medium sized hoses got to the same spots on both sides, the one small hose on the possible newer side gets hooked up on top with a 90* instead of on the side like the rest.

now that I think about it. The side I assume has been replaced…… the smaller hose that has the 90* is getting plumbed right to the apply piston on the motor for the high speed travel, well I’m pretty sure that’s the circuit it’s plumbed to. Which means it’s operating the piston directly from where the other side just has a plug

 

[uffex]

Good day RPF
I would suggest miss match drive motors creates a big question in my mind, if you measure the speed of each motor in low speed any difference will already represent part of the issue, again in low speed in both directions is it the same motor that remains lame. See attached.
Kind regards
Uffex

 

[RPF207]

Yup, same motor remains somewhat lame in both directions

 

[RPF207]

Could I try plumbing it how they have on the good side?