Automatic Transmission Jerking, Slipping or Slow to Engage?

Short answer: Jerking, slow engagement when cold, high revs with little movement, extra heat and fluid leaks are the main warning signs.

Common signs are jerking or banging when the gear changes, the gear taking from a few seconds to a few minutes to engage on a cold morning, the engine revving high while the car hesitates or struggles uphill, the gearbox running hot, and fluid spots under the car.

Short answer: Often hydraulic pressure loss from ageing seals. Low or old fluid, solenoid faults and worn clutches can also cause it.

Most often the gearbox can no longer hold the pressure it needs to change gear smoothly, usually because internal parts have aged. Low or old fluid can also cause it, so check the fluid level first.

Short answer: Hardened seals leak pressure while the gearbox is cold, until it warms up.

When the gearbox is cold, ageing parts are at their stiffest and pressure leaks away, so the gear can take from a few seconds to a few minutes to engage. It often improves once the car warms up, a typical early sign that treatment can help.

Short answer: Your gearbox is slipping, usually because it is losing pressure.

The gearbox is slipping: power is lost before it reaches the wheels. You’ll often notice it most when climbing hills or accelerating hard.

Short answer: Not for long. Treat it early, and stop driving if the car won’t move in any gear or smells burnt.

Mild symptoms usually get worse over time, and slipping creates heat that wears the gearbox faster. Treat early. If the car won’t drive in any gear or smells burnt, stop and see a workshop.

Short answer: Yes, if the slipping comes from pressure loss and nothing is broken.

It can’t repair broken parts, worn-out clutch plates or electronic faults.

Short answer: Add one 150 ml bottle to the gearbox and drive as normal.

Add one 150 ml bottle into the automatic gearbox. One bottle treats 4 to 6 litres of transmission fluid. Drive as normal.

Short answer: Usually within a few hours to 48 hours of normal driving.

Short answer: It lasts, because Fix-IT revitalizes the seals instead of softening them.

Softened seals keep swelling and eventually fail, while revitalized seals keep their shape without excessive swelling. In our experiment, a hardened seal from a malfunctioning transmission was cut into two pieces of the same length and weight. After 3 years in ATF with 4% KM+ AT Fix-IT, the soaked piece gained only 2–4% in weight and stretched 7 cm under a 14-newton pull, while the dry piece stayed hard and could not be stretched.

Short answer: Not straight away. Change it at your next scheduled service.

Leave Fix-IT in and change the fluid at your next scheduled service.

Short answer: Yes. It works in AT, CVT, wet-clutch DCT/DSG and hybrid automatic gearboxes.

It suits 4- to 9-speed automatics, hybrid automatics, CVTs, and DCT/DSG gearboxes with wet clutches.

Short answer: No. Fix-IT revitalizes seals; stop-leaks swell and soften them.

Stop-leak and seal-softening products swell and soften seals for a temporary fix, and after a few treatments the seals lose their shape and are destroyed. Fix-IT is a seal revitalizer: it restores the elasticity of hardened seals without making them swell excessively. In our experiment, a hardened seal from a malfunctioning transmission was cut into two pieces of the same length and weight. After 3 years in ATF with 4% KM+ AT Fix-IT, the soaked piece gained only 2–4% in weight and stretched 7 cm under a 14-newton pull, while the dry piece stayed hard and could not be stretched.

Short answer: No harmful swelling. The small 2–4% weight gain in our 3-year test comes from the seal regaining flexibility.

That is the difference between a seal revitalizer and a seal softener. In our experiment, a hardened seal from a malfunctioning transmission was cut into two pieces of the same length and weight. After 3 years in ATF with 4% KM+ AT Fix-IT, the soaked piece gained only 2–4% in weight and stretched 7 cm under a 14-newton pull, while the dry piece stayed hard and could not be stretched. Seals soaked in a seal-softening liquid, by contrast, swelled and deformed.

Short answer: When the fault is mechanical or electronic rather than hydraulic.

When parts are broken, clutch plates are worn out, the fault is electronic, or another seal-softening product has already been used. If you’re unsure, ask a workshop to check first.

Short answer: Fix-IT repairs a problem; Nano ATF Treatment is regular maintenance.

Fix-IT is for a problem you have now. Nano ATF Treatment is regular maintenance that keeps the gearbox smooth and helps stop the problem coming back.

Short answer: 99.5% in qualifying cases. Of more than 200,000 bottles sold since 2019, fewer than 200 cases were reported as not solved.

We quote a conservative 99.5% because not every customer reports back; reported unresolved cases are under 0.1%. It applies when the problem has been assessed by a workshop, no seal-softening liquid has been used, parts are original or good quality, and nothing is broken.

Short answer: In most cases, yes: when the problem is pressure loss in the hydraulic control system.

Since 2019, KM+ has sold more than 200,000 bottles for cars of all major brands and gearbox types, including Aisin, ZF and Jatco gearboxes, CVTs, wet-clutch DCTs and hybrid automatics. In our experience, when the problem is pressure loss in the hydraulic control system, meaning the gearbox is losing the pressure it needs, the same treatment principle applies across gearbox brands and designs. The few cases where it did not work involved broken parts, worn-out clutch plates, electronic faults, or another seal-softening product already in the gearbox.

Short answer: Yes. It works on the hydraulic control system, whoever made the gearbox.

Fix-IT works on the hydraulic control system that conventional automatics, CVTs, wet-clutch DCT/DSG and hybrid automatics all rely on, whoever made the gearbox. Since 2019 it has been used in cars of all major brands, with gearboxes from Aisin, ZF, Jatco and the carmakers themselves. Send us your car model, year and gearbox type on WhatsApp and we’ll check it against our case records.

Short answer: While your car is under warranty, follow the carmaker’s advice. Fix-IT is a remedial option for out-of-warranty gearboxes that are already losing pressure.

Gearbox makers give general advice against additives because many products, such as friction modifiers or stop-leaks that swell seals, can change how the gearbox behaves. Fix-IT is used when a gearbox is already showing signs of pressure loss in its hydraulic control system and the alternative is an expensive overhaul or replacement. It has resolved problems in gearboxes of many brands that workshops had been unable to fix. If you’re unsure, ask a workshop to assess the gearbox first.

Short answer: Yes, for hybrid gearboxes with hydraulic control. Hybrid electrical faults need a separate check.

It is made for hybrid automatic gearboxes as well as conventional automatics, CVTs and wet-clutch DCTs. Hybrid gearboxes depend on precise hydraulic control to switch between the engine and the electric motor, so pressure loss can show up as loss of power, jerking or stalling during the handover. Faults in the hybrid battery, inverter, electric motor or control electronics can cause similar symptoms and need a separate check by a workshop.

Short answer: It may. If your car is under warranty, check with your dealer first.

Adding any product to a gearbox may affect a manufacturer’s warranty. If your car is still under warranty, check with your dealer first. For cars out of warranty, Fix-IT is a low-cost step to try before an overhaul, as long as no parts are broken.