Why Won't Your Excavator Track on One Side?
And why pulling the final drive first is usually the expensive mistake
The call we get is usually the same: one track has gone dead, or it's turning noticeably slower than the other. By the time anyone reaches us, the assumption is already made — final drive's gone, book the replacement.
That assumption is expensive if it's wrong. A final drive isn't a cheap part, and if the actual fault is a brake that isn't releasing, a crushed hose, or leakage inside the travel motor, you've pulled the wrong component and the machine still won't track straight. Before anything gets removed, there's a sequence of questions and checks that narrows this down — most of them free, done with the machine as it stands.
The symptoms people describe
"One side's completely dead — nothing at all." A total loss usually points to something seized or fully blocked, not gradual wear.
"It's not stopped, just slower on one side." Partial movement usually means internal leakage or a restriction, not a locked component.
"It's fine forward but weak in reverse" (or the other way round) A fault that only shows up in one direction points at the pilot circuit or the travel control spool on that side — not the final drive.
"It gets worse the longer the machine runs." The signature of internal leakage in the travel motor. Hydraulic oil thins as it heats, leakage increases, and torque drops off.
"It happened overnight" versus "it's been getting worse for weeks" Sudden failure points to something mechanical seizing. Gradual decline points to wear or leakage building over time.
Questions to answer before you touch anything
Is it completely dead, or just slower than the other side? Dead usually means something's seized or blocked. Slower usually means a leak or restriction.
Does it happen in both directions, or only one? Direction-specific faults point at the pilot circuit or travel spool, not the final drive.
Hot, cold, or does it get worse as the machine warms up? Getting worse with heat is the signature of internal motor leakage.
Does the engine labour when you try to move that track, or does the note stay the same? Heavy load means something mechanical is resisting — final drive, a brake not releasing, or a seized motor. No change in engine note means hydraulic oil isn't reaching the motor at all.
Can you hear the travel motor turning? Confirms whether oil is reaching the motor and it's spinning, even if the track isn't responding.
Any grinding or clicking from the final drive? Early warning of gear damage inside the final drive itself.
Did it happen suddenly, or has it worsened over time? Sudden points to mechanical seizure. Gradual points to wear or leakage building.
Has anyone recently worked on the final drive, drivetrain, travel motor, or hydraulic system? Recent work is often the actual cause, not a coincidence.
The checks, in order
Inspect the undercarriage first — before touching any hydraulics. Track tension, bent track guards, an obstruction in the chain, a bent guide, seized rollers. Any of these can slow or stop a track, and none of them cost anything to check.
Pull the final drive plug and check the oil. Level first, then inspect the magnetic plug for debris and smell the oil for a burnt note. Clear oil and a clean plug — the final drive is probably still good.
Raise the machine and run the affected track off the ground, with no load on it. If the problem improves or disappears once the load is removed, it's load-related. If it's identical in the air, the fault sits inside the drive line itself.
Compare engine loading and track speed, good side against faulty side. Listen to what the engine does on the working track versus the affected one.
Now the tests
Check pilot pressure and confirm full spool movement on the travel circuit, faulty side.
Run a case drain test on the affected travel motor. There's no single spec that covers every make and model — if you can get the manufacturer's figure for that specific motor, use it. If you can't, run the same test on the good side and compare the two, at the same oil temperature. A significant difference between the two sides confirms internal leakage — this is the test that actually proves a failed motor, rather than assuming one from the symptoms alone.
Check that the parking brake is releasing fully, and inspect the counterbalance valve. A brake that isn't releasing, or a valve that's sticking, can present almost identically to a mechanical failure — and costs nothing like one to fix.
Quick reference
What you're seeing | Most likely cause |
Engine loads heavily, track doesn't move | Something seized or mechanically restricted — final drive, a brake not releasing, or a seized travel motor |
No load on the engine at all | Hydraulic oil isn't reaching the motor — there's no resistance for the engine to feel |
Track only works in one direction | Pilot circuit or travel control spool fault on that side |
Works fine in the air, weak on the ground | Low-torque problem — weak travel motor, low hydraulic pressure, or a dragging brake |
Gets weaker as the machine heats up | Internal leakage in the travel motor, more noticeable as the oil thins with heat |
Metal in the final drive oil or on the magnetic plug | Internal damage to the final drive — it needs to come out for inspection |
Why this matters
Most of these checks cost nothing but the time to do them properly. The two that do cost something — a pressure gauge, a case drain flow test — still cost far less than a final drive ordered on assumption. We'd rather work through this sequence with you and find out the final drive was never the problem than sell you one it turns out you didn't need.
If you're chasing a track that won't move, or won't move evenly, send us what you've found working through the checks above — we'll help you get to the actual fault before anything gets ordered.
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