Singapore's Best EV Reduction Gearbox Overhaul Specialists

Most electric cars have no clutch and no gears to shift, so owners are told there is nothing in the drivetrain to go wrong. There is. Between the motor and the wheels of almost every EV sits a single-speed reduction gearbox: a pinion on the motor shaft, an intermediate gear, a final drive and the differential, all running in gear oil on a set of bearings. It steps the motor's very high revs down to wheel speed and multiplies the torque. Every metre you drive goes through it, and every time you lift off, regen braking loads the same gears in the opposite direction.

That is a hard life for a small unit. The bearings are the usual weak point. Once a bearing starts to pit, it whines, then it rumbles, and the fine metal it sheds circulates in the oil and eats into the gear teeth and the other bearings. Left alone, the gearbox eventually stops transferring drive cleanly and the car feels like it is slipping, even though an EV has nothing to slip. The gear oil is the forgotten fluid too. Many owners are told it never needs changing, so the unit runs its whole life on oil that broke down long ago.

The good news: this is a gearbox, and rebuilding gearboxes is what we do. The motor, the inverter and the high-voltage battery are separate systems. They are not opened or overhauled in this job, even on cars where the whole drive unit has to come out to reach the gearbox.

If you drive a first-generation Hyundai Kona Electric, a Kia Niro EV or the original Hyundai Ioniq Electric and you hear a rumble or whine from the front, you are not imagining it. Hyundai issued a service bulletin for an abnormal rumble from the motor and reduction gear on 2019 to 2021 Kona Electric cars built up to January 2021. Its procedure runs from a motor mount bracket through to inspection and replacement of the motor or the reduction gear. Kia issued the equivalent for the Niro EV from the 2019 model year, with the same low-speed rumble and the same motor-or-reduction-gear inspection. The original Ioniq Electric is from the same era of Hyundai EV drive units, and the one on our bench in the teardown photos on this page is exactly that car: worn bearings and gear surfaces inside the reduction gearbox.

Two things matter here. First, an overseas bulletin does not tell you which Singapore cars are affected or whether the agent will cover yours. If the car is still under the agent's warranty, use it. Second, the bulletin remedy for a worn unit is a new motor or a new reduction gear, which is fine while someone else is paying. Once the car is out of warranty, we diagnose it the same way the bulletin does. If it is the mount, we fix the mount. If the reduction gearbox itself is worn, that is an overhaul job at a sensible price, with new bearings and gears in your own casing and a 2 year / 40,000km warranty on the work.

Newer Hyundai EVs are a different story. The 2023 to 2024 Ioniq 5 and the 2024 second-generation Kona Electric had a factory campaign for an incorrect oil quantity in the motor and reduction gear, which can grind or whine. The fix there is a drain and refill to the correct level, not an overhaul. If your car is in that group, that is the first thing we check.

Ask an agent about a noisy EV gearbox and the answer is usually a complete drive unit, sometimes motor and gearbox together as one sealed assembly, on a parts wait. Most are not set up to open it. On a car that is a few years old, that bill can rival the value of the car.

We open it. An overhaul strips the reduction gearbox, replaces the worn bearings, gear components, seals and gaskets with quality OEM-grade parts, and rebuilds it in your own casing with fresh EV-grade gear oil. You keep a healthy motor, you keep a healthy battery, and you pay for what was actually worn. Where a unit is truly beyond overhaul, a cracked casing or gear teeth that have let go, we tell you straight and quote the honest alternative.

The result is backed by the longest warranty in Singapore: 2 years or 40,000km on every EV reduction gearbox overhaul.

This is not theory. A Hyundai Ioniq Electric came to us losing drive, with an abnormal noise from the gearbox area and the motor spinning without the car pulling. We confirmed the motor was healthy, removed the reduction gearbox and stripped it: worn gear surfaces and bearing wear, far enough gone that the unit could no longer transfer drive cleanly. We overhauled it with new internals, refilled it with the correct EV-grade gear oil, refitted it and road tested it until drive was fully restored and the noise was gone. The job came to $3,800 before GST and carries our 2 year / 40,000km warranty.

The teardown photos on this page are from that car. Read the full Hyundai Ioniq Electric gearbox overhaul case study.

A faint whine is a warning, not an emergency. A rumble that is getting louder, grinding, a new vibration or any loss of drive is the gearbox telling you the metal has started to move. Every kilometre from that point spreads debris through the oil and turns a bearing job into a gears-and-bearings job, or worse, a unit that seizes and leaves you stopped in the outside lane of the PIE with the hazards on.

If the car has lost drive or the noise has turned to grinding, stop somewhere safe and WhatsApp us. Towing is free if the car cannot move, and it goes on a flatbed. An EV should never be towed with its driven wheels rolling on the road, because the motor keeps turning and can damage itself and the drive electronics.

1 Car Service is Singapore's best EV reduction gearbox overhaul specialist. The team that has rebuilt thousands of gearboxes, from PDK and DSG to CVT, now does the same for electric cars of every make and model. We pinpoint the real fault with dealer-level diagnostics, rebuild the reduction gearbox properly in your own casing, and back every overhaul with the longest warranty in Singapore: 2 years or 40,000km. Free honest diagnosis, free towing if the car cannot move, and you can spread the cost with Atome, Grab or Shopee.

WhatsApp us now with your model, year and what the car is doing. We'll sort your EV gearbox for good.