Hyundai 360 Swing Motor, help? Pinion Seized?

This is my first experience troubleshooting/repairing swing motors. I did not diagnose this machine though I feel more diagnosis should have been made before condemning this pump. Its a Hyundai 360 excavator, long reach style, about 10 years old. I have removed the pump from top of gear box, everything in or around gears looks fine. THE PINION GEAR SHAFT WILL NOT ROTATE, is this normal for swing motors? I have tried rotating it with quite a bit of force.

I understand that most of these motors have brakes (clutch pack) that must be released before pump can drive, is that why the shaft will not rotate?

Yes, if there is a small 1/2" line or so. That will be the release pressure on teh brake

Good day Broiesel
If the swing transmission has an issue it will show up by draining some of the lube from the box mostly this will have witness parts of a failure.
Kind Regards
Uffex

This link may help you
KR
Uffex

https://www.heavyequipmentforums.com/attachment.php?attachmentid=161941&d=1480326950

Brodiesel said:

This is my first experience troubleshooting/repairing swing motors. I did not diagnose this machine though I feel more diagnosis should have been made before condemning this pump. Its a Hyundai 360 excavator, long reach style, about 10 years old. I have removed the pump from top of gear box, everything in or around gears looks fine. THE PINION GEAR SHAFT WILL NOT ROTATE, is this normal for swing motors? I have tried rotating it with quite a bit of force.

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Do you mean the pinion shaft on the box or do you mean the shaft at the bottom of the motor? As you've mention there's a spring applied disk brake on the motor which is released by 40 bar of pressure normally by an external hoses. With the motor removed, you won't be able to turn the shaft unless the brake is released.
If its the pinion shaft on the box, then with the motor removed, if you can lift the bucket slightly off the ground( you'll need to blank all the swing motor hoses off), you should be able to easily pull the machine round in a circle by hand if its on a level surface. If not the issues definitely in the swing box.

Pinion shaft at the bottom of the motor. By hand? This machine is huge! Im going to reinstall and take 40bar/600psi measurement at brake line. Thanks!

"Tested" swing motor. The pinion was spinning in either direction consistently. But, once installed into gear box the machine will not rotate. Could it be a flow issue? Or is the problem further down into gear box? Hmmm

When installed, what is the pressure on the FWD and REV ports?