Lost drive, or stuck in one gear?
If the car suddenly won't drive, revs without moving, or locks into one gear, pull over somewhere safe as soon as you can and switch off. Hazard lights on, and if you're beside traffic, everyone waits outside on the side away from it. Don't force the lever or keep trying to drive it. Ring your roadside cover, and call 111 if anyone is hurt or in danger.
Which kind of gearbox is in your car?
A manual has a clutch pedal, and most of its problems are clutch problems. A conventional automatic uses a fluid coupling and sets of gears. A CVT (continuously variable transmission) uses a belt or chain between two pulleys instead of fixed gears, and it's very common in small Japanese cars, imports included.
Dual-clutch automatics, found in plenty of European cars, are really two manual gearboxes run by a computer. Hybrids such as the Aqua and the Prius use a different design again. The owner's manual names the type, and the type decides the fluid and the kind of garage you want.
What the gearbox might be telling you
| What it can mean | What to do | |
|---|---|---|
| Revs rise but the car doesn't speed up | Slipping: low or old fluid, or wear inside | Have it checked before it gets worse |
| A clunk or long pause going into Drive | Fluid, a control fault, or worn engine mounts | Get it checked soon and note when it happens |
| A whine that rises with speed | Often a CVT belt or bearing, or low fluid | Get it looked at; whines rarely fix themselves |
| A shudder pulling away | Torque converter, clutch packs or a dual-clutch issue | Note the speed it happens at for the mechanic |
| A warning light and very little power | Limp mode: the computer protecting the gearbox | Drive gently to a safe stop and get it checked |
| Red or brown drips under the car | A transmission fluid leak | Photograph it and say so in the note |
Do I need a transmission fluid change?
Look in the maker's schedule. Some list a change at a set distance, some only under hard use like towing, hills or stop-start traffic, and some call the fluid long-life. AA New Zealand says automatic transmission fluid ages from bright red to brown. Dark fluid that smells burnt has been working too hard for too long.
The fluid has to be exactly the type the maker specifies. CVTs in particular need their own fluid, and the wrong one can damage the gearbox. Many newer automatics have no dipstick at all, so checking the level properly is a garage job.
What does the mechanic do?
They'll read the fault codes, check the fluid level and condition, and take the car for a drive to feel the fault for themselves. Mounts, linkages and software updates get a look too, because not every shudder lives inside the gearbox.
From there the options run from a fluid service, to repairing a valve body or a solenoid, to rebuilding or replacing the gearbox. If they recommend a replacement, ask whether it's new, reconditioned or used, and what warranty comes with it.
A WoF won't tell you how the gearbox is
A WoF inspection is about safety items like brakes, tyres and steering. Consumer Protection points out that a valid warrant doesn't mean a car is mechanically sound, so a gearbox can be on its way out on a car with a fresh sticker.
General garages handle fluid changes and the first diagnosis. Rebuilds usually go to a transmission shop. A local mechanic who specialises in your car.
What the written quote should show
- The fault codes found and what the road test showed.
- The fluid type and how much, named to the maker's specification.
- Whether the work is a fluid service, a repair, a rebuild or a replacement.
- For a replacement gearbox: new, reconditioned or used, and its warranty.
- Any software update or relearn the gearbox needs after the work.
What you can do, and what to leave
You can
- Note when the fault shows up: cold or hot, at what speed, uphill or on the flat.
- Film the shift or record the noise on your phone.
- Find the gearbox type and any fluid change history in the manual and service records.
- Look for red or brown drips where the car parks.
Leave to the mechanic
- Checking and changing the fluid, especially on sealed gearboxes without a dipstick.
- Reading fault codes and running relearn procedures.
- Anything inside the gearbox, and removing or fitting one.
If it were our car
We'd get a slipping or whining gearbox looked at within days, because small faults get expensive when they're driven on. Put the gearbox type and what it's doing in the note. If the car is due a fluid change on the maker's schedule and never had one, that's an easier conversation to have before symptoms start.