Quick Answer: A zero-turn mower that pulls to one side, drifts off a straight line, or has stiff/sloppy lap bars is almost always a tire-pressure mismatch or a tracking (neutral) adjustment issue — not a failing transaxle. Check that both rear tires are at the same PSI first (a 3-4 psi difference is enough to cause drift), then adjust the tracking bolt on the linkage between the faster-spinning wheel’s lap bar and its pump in small increments until both sides match. Stiff or non-centering bars usually trace to dirt or a stretched return spring at the linkage, not a hydraulic fault.
Steering problems are a different animal from a mower that won’t move at all — if your zero-turn won’t drive in any direction, see our zero-turn mower won’t move guide for bypass-valve and belt checks instead. This guide covers a mower that drives fine but won’t hold a line, feels lopsided, or has levers that don’t move or return the way they should.
1. Check tire pressure side-to-side first
| Symptom | Likely cause | Fix |
|---|---|---|
| Mower drifts left or right with both bars pushed evenly | Mismatched rear tire pressure or a tracking/neutral adjustment off | Equalize PSI first, then adjust tracking bolt if drift remains |
| One lap bar feels stiff or heavier than the other | Dirty or dry linkage pivot points | Clean and lubricate the control rod pivots under the seat |
| A bar doesn't snap back to neutral on its own | Stretched, disconnected, or broken return spring | Inspect and replace the spring on that side |
| Mower steers fine on pavement but drifts on grass | Uneven tire tread wear or turf traction imbalance | Check tread depth match and tire condition side-to-side |
| Forcing the mower straight causes a whining noise | Hydro pump loaded up compensating for bad tracking | Stop steering against it — fix tracking instead, per Toro's own service guidance |
Before touching any linkage, check both rear drive tires with a low-pressure gauge — most residential zero-turns spec roughly 12-14 psi in the rear per Toro, Cub Cadet, and Husqvarna owner’s manuals (see our tire pressure guide for the full brand-by-brand table), and even a 3-4 psi gap side-to-side is enough to make the mower pull noticeably during straight passes. It’s the fastest and cheapest check on this list, and it rules out the most common non-mechanical cause before you start turning adjustment bolts.
Low-pressure digital tire gauge
- Check both rear tires before assuming a tracking or hydro problem.
- A standard automotive gauge isn't precise enough in the 10-14 psi turf-tire range.
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2. Adjust the tracking (if tires already match)
A zero-turn steers by running two independent hydrostatic pumps, one per rear wheel, at whatever speed each lap bar commands — for the mower to drive straight, both pumps have to deliver identical output when both bars are pushed forward the same amount. If tire pressure is already even and the mower still pulls, one pump is putting out slightly more flow than the other, and the fix is a tracking (sometimes called neutral) adjustment on the link rod connecting that lap bar to its pump arm.
The general procedure, consistent across most Hydro-Gear-equipped mowers and documented in Toro’s and Cub Cadet’s own service materials: get the mower on level ground with both rear wheels safely off the ground on stands, start the engine, and push both bars forward the same amount. Whichever wheel spins faster is the side to adjust — loosen the tracking bolt or nut on that side’s linkage and turn it in small quarter-turn increments, retesting after each turn, until both wheels match speed. Small, incremental adjustments matter here; overcorrecting in one big turn tends to just flip the drift to the opposite side.
3. Don’t compensate by oversteering
It’s tempting to just muscle the mower straight by holding one bar back slightly to counter a known pull, especially mid-mow when stopping to adjust linkage isn’t convenient. Toro’s own TimeCutter service documentation specifically warns against this: forcing an untracked unit to drive straight loads up the hydro pump on the resisting side, which can make it whine under strain and, on turf, can tear the grass where the mismatched wheel speed is fighting the ground. A mower that needs to be steered straight has a tracking problem that needs the actual adjustment in Step 2, not a permanent workaround.
4. Diagnose stiff or non-centering lap bars
If the mower tracks straight but a lap bar feels stiff, sticky, or doesn’t snap back to neutral cleanly when released, the problem is almost always mechanical rather than hydraulic — dirt, dried grass clippings, and surface rust accumulate on the exposed control-rod pivots and linkage points under and behind the seat over a season of mowing. Clean the visible pivot points and apply a light machine oil or dry lubricant, then work the bar through its full range a few times. If a bar still won’t self-center after cleaning, check the return spring on that side; a stretched, disconnected, or broken spring is a common failure point and is a simple, inexpensive part to replace. Persistent vibration through the bars during operation, rather than stiffness, points to a different issue — see our spindle replacement guide if that’s what you’re feeling instead.
When it’s a bigger repair
If tire pressure is matched, the tracking adjustment is centered as far as the bolts allow, and linkage is clean and moving freely, but drift or stiffness persists, the issue has likely moved inside the transaxle itself — a worn charge pump or internal wear that a linkage adjustment can’t compensate for anymore. That’s the same threshold covered in our won’t-move guide: a dealer-level repair on most residential and mid-commercial units, since transaxles are largely sealed assemblies. Check OEM vs. aftermarket parts pricing before booking a service appointment if a dealer quotes a linkage or pump replacement.
The bottom line
Work the list in order: tire pressure first since it’s the fastest and cheapest check, then the tracking adjustment if pressure already matches, then the linkage itself if the bars feel physically stiff or won’t center. Resist the urge to just steer against a known pull — per Toro’s own guidance, that strains the hydro pump instead of fixing the actual cause. Most steering complaints get resolved with a gauge and a wrench in the driveway; a transaxle-level repair is the exception, not the starting assumption.