| Step | How | Conclusion |
|---|---|---|
| 1. Swap lines | Swap left/right travel lines, retest | Fault moves = upper (swivel joint / main valve); stays = lower |
| 2. Gauge pressure | Test both travel circuits | Chase the low side; both low = pilot or main pump |
| 3. Final-drive oil | Check the gear oil level plug | Low oil = motor/final-drive internal leak; full = lower unit cleared |
The center swivel joint feeds every line between upper and lower structure and rotates all day. Worn seals let high-pressure oil cross over to the low-pressure side — tracking pull, one-sided weakness, even weak swing. A seal kit costs a fraction of pulling a travel motor, which alone is ten times the labor.
Boundary: fault doesn't swap + low final-drive oil + motor noise = open the motor / reduction gear path.
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The core must be extracted — best done by a mechanic. Send the model first so we match the seal kit.
Yes, done slowly in open space with a hydraulically literate person swapping lines.
Even more likely multi-port swivel crossover — check it first.
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