Pc75uu2 final drive issue

[Floresfarm]

Hello, I just recently replaced a final drive on my excavator. I Bought the final drive from Ali Baba because Komatsu discontinued them. The problem I’m having is after about 5 minutes of use the new final drive will start to track a lot faster than the original one. It will also struggle to turn left to right. Also I can hear a noise coming from the final drive when the stick is fully extended. Not a bad noise just sounds like the gears are turning faster kinda like a zipper on a coat. If I let the machine sit for a little bit hour or so it will be back to normal working condition until after using it for 5 min and then do the same thing. If anyone has any thoughts can you please chime in. Thank you very much, Mike

 

[coalrulz]

Did the new final Drive have 1 additional hydraulic port compared to the original?

 

[Floresfarm]

It did have one additional port. What are you thinking?

 

[coalrulz]

I am wondering if the final drive motor that you recently purchased is a two-speed motor.
From everything I can find the PC75UU-2 was equipped with single speed hydraulic travel motors. If the motor you purchased is two speed, for PC75UU-3, and you hooked up the case drain hose to the motor port that is supposed to feed the two speed servo you could get the symptoms you describe. The case drain pressure in the motor builds until it shifts the two speed servo increasing one track speed, shut machine off for a while case drain pressure drops. Bad thing about this if I am right the case drain pressure will build to high and blow out motor shaft seal.

 

[Floresfarm]

Did the new final Drive have 1 additional hydraulic port compared to the original?

Yes I just checked and it did have additional port.

 

[Floresfarm]

I am wondering if the final drive motor that you recently purchased is a two-speed motor.
From everything I can find the PC75UU-2 was equipped with single speed hydraulic travel motors. If the motor you purchased is two speed, for PC75UU-3, and you hooked up the case drain hose to the motor port that is supposed to feed the two speed servo you could get the symptoms you describe. The case drain pressure in the motor builds until it shifts the two speed servo increasing one track speed, shut machine off for a while case drain pressure drops. Bad thing about this if I am right the case drain pressure will build to high and blow out motor shaft seal.

I think your right that makes a lot of sense. So would I be able to rearrange the plumbing to the drive motor for it to work properly?

 

[chardengine]

Hello, I just recently replaced a final drive on my excavator. I Bought the final drive from Ali Baba because Komatsu discontinued them. The problem I’m having is after about 5 minutes of use the new final drive will start to track a lot faster than the original one. It will also struggle to turn left to right. Also I can hear a noise coming from the final drive when the stick is fully extended. Not a bad noise just sounds like the gears are turning faster kinda like a zipper on a coat. If I let the machine sit for a little bit hour or so it will be back to normal working condition until after using it for 5 min and then do the same thing. If anyone has any thoughts can you please chime in. Thank you very much, Mike

Hi you mean the whole final drive or just the floating seal / du cone seal?

 

[coalrulz]

Image below is from the PC75UU-3 manual, roughly showing the hose routing to what appears to be the left track travel motor. Case drain is shown as #2, hose #3 would be the two speed travel hose, which I am assuming you do not have.
Are the motor ports identified with letters and numbers that correspond with the diagrams below? C1, C2, P1, P2, etc.


Below diagram is from PC75UU-3. Port C1 is two speed travel.



Below diagram is from PC75UU-2. Port C1 is case drain.