Symptom
Whine or hum from the transmission
A whine, hum or moan from the gearbox rather than the engine: it changes between neutral and drive, follows road speed rather than engine revs, or — on gearboxes with their own electric pump — is that pump audibly running at odd moments or near-continuously. On a conventional automatic, a whine that worsens when the fluid is low is the pump drawing air, which is the cheapest warning the transmission ever gives. A whine only under hard acceleration points at the turbocharger instead, and a smooth rising electric note on a hybrid is the drive motor — both have entries of their own.
Also described as: transmission whine, gearbox whine, whining from the gearbox, transmission noise, gearbox noise, gearbox pump running, pump running constantly, cvt whine, whine in gear, gearbox humming, whining from the transmission, transmission pump running, transmission humming, زوزه گیربکس, صدای هوم از گیربکس, zumbido caja, ruido transmision, chirrido caja cambios, أزيز من الجير, صوت من ناقل الحركة, طنين من الغيار
Some causes mean you should stop driving
1 of the 9 codes that produce this symptom indicate a fault where continuing to drive risks damage or is unsafe. If the symptom is sudden or severe, treat it as one of those until a scan says otherwise.
What this usually means
Establish what the noise follows, because that separates three different systems. A noise that follows road speed and changes between neutral and drive is the transmission. A noise that follows engine speed under hard acceleration is more likely the turbocharger. A smooth rising electric note on a hybrid is the drive motor, and all three have entries of their own.
On a conventional automatic, a whine that worsens when the fluid is low is the pump drawing air — and it is the cheapest warning the transmission ever gives. A pump that is cavitating is not making full pressure, so the clutches it serves are already being under-clamped; acting on the noise at that point is a fluid leak repair, and ignoring it is an overhaul. That single fact makes this symptom worth more than its low code count suggests.
On gearboxes with their own electric pump, the noise may be that pump running when it should not. An auxiliary pump that runs near-continuously, or comes on at odd moments, is usually compensating for pressure it cannot maintain — so it is a symptom of a leak or a failing main pump rather than a noisy component.
Mechanical whine that varies with road speed and is unaffected by fluid level points at gears and bearings — final drive, differential, or an output bearing. A whine that changes when you lift off or apply power is characteristic of gear mesh loading and unloading, and is a different repair from a bearing, which whines steadily regardless.
Working through it
| What you find | Likely cause | How to confirm it | What fixes it |
|---|---|---|---|
| Whine worsens as fluid level falls, or on hard cornering | The pump drawing air — the cheapest warning the transmission gives | Check level by the manufacturer's procedure, and note whether the noise correlates with cornering, which uncovers the pickup. | Find the leak and correct the level immediately. Acting here is a seal; ignoring it is an overhaul. |
| Noise changes between neutral and drive | Inside the transmission — a loaded component rather than an engine-driven one | Compare deliberately in neutral and in drive at a standstill. A difference localises it past the engine. | Diagnose inside the transmission. This test alone rules out most engine-bay candidates. |
| Follows road speed, unaffected by fluid level, steady | A bearing — output, final drive or differential | A bearing whines steadily regardless of load, where gear mesh noise changes on and off throttle. | Renew the bearing. Check the fluid for metal, which tells you how far it has gone. |
| Whine changes when you lift off and again on power | Gear mesh loading and unloading — worn or incorrectly set final drive gears | Note the on-throttle and off-throttle difference; it is the classic discrimination from a bearing. | Set up or renew the final drive. A different and larger job from a bearing, which is why the test matters. |
| Electric pump audible near-continuously or at odd moments | The auxiliary pump compensating for pressure that is not being held | Read the pump's live duty where the tool exposes it, alongside line pressure. | Repair the leak or the main pump. The noisy auxiliary is the symptom rather than the fault. |
| Only under hard acceleration, rising with engine speed | The turbocharger rather than the transmission | Follow engine speed rather than road speed. Neutral revving reproduces it if it is the turbo. | Diagnose as a turbo noise; it has its own entry in this vocabulary. |
-
Whine worsens as fluid level falls, or on hard cornering
- Likely cause
- The pump drawing air — the cheapest warning the transmission gives
- How to confirm it
- Check level by the manufacturer's procedure, and note whether the noise correlates with cornering, which uncovers the pickup.
- What fixes it
- Find the leak and correct the level immediately. Acting here is a seal; ignoring it is an overhaul.
-
Noise changes between neutral and drive
- Likely cause
- Inside the transmission — a loaded component rather than an engine-driven one
- How to confirm it
- Compare deliberately in neutral and in drive at a standstill. A difference localises it past the engine.
- What fixes it
- Diagnose inside the transmission. This test alone rules out most engine-bay candidates.
-
Follows road speed, unaffected by fluid level, steady
- Likely cause
- A bearing — output, final drive or differential
- How to confirm it
- A bearing whines steadily regardless of load, where gear mesh noise changes on and off throttle.
- What fixes it
- Renew the bearing. Check the fluid for metal, which tells you how far it has gone.
-
Whine changes when you lift off and again on power
- Likely cause
- Gear mesh loading and unloading — worn or incorrectly set final drive gears
- How to confirm it
- Note the on-throttle and off-throttle difference; it is the classic discrimination from a bearing.
- What fixes it
- Set up or renew the final drive. A different and larger job from a bearing, which is why the test matters.
-
Electric pump audible near-continuously or at odd moments
- Likely cause
- The auxiliary pump compensating for pressure that is not being held
- How to confirm it
- Read the pump's live duty where the tool exposes it, alongside line pressure.
- What fixes it
- Repair the leak or the main pump. The noisy auxiliary is the symptom rather than the fault.
-
Only under hard acceleration, rising with engine speed
- Likely cause
- The turbocharger rather than the transmission
- How to confirm it
- Follow engine speed rather than road speed. Neutral revving reproduces it if it is the turbo.
- What fixes it
- Diagnose as a turbo noise; it has its own entry in this vocabulary.
Codes that produce this symptom (9)
Listed with the codes that most typically present this way first — the likeliest place to start.
- P0943 Hydraulic Pressure Unit Cycling Period Too Short Typical of this code High
- P0947 Hydraulic Pump Relay/Control Circuit Low Typical of this code High
- P0868 Transmission Fluid Pressure Low Stop driving High
- P0933 Hydraulic Pressure Sensor Range/Performance High
- P0936 Hydraulic Pressure Sensor Circuit Intermittent High
- P0B02 Electric/Auxiliary Transmission Fluid Pump Motor Phase U Current High Moderate
- P0C26 Electric/Auxiliary Transmission Fluid Pump A Motor Current High
- P0C27 Electric/Auxiliary Transmission Fluid Pump A Motor Current Low Moderate
- P0C28 Electric/Auxiliary Transmission Fluid Pump A Motor Current High Moderate
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
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