A transmission bolted to a repair stand while a mechanic works on it with a hand tool

Transmission acting up? Start here.

Slipping, a hard clunk into gear, or a car that won't shift at all. Call and describe what it's doing. That alone narrows it down a lot.

Call (502) 267-7561 Fax (502) 267-7596

What the car is telling you

Most transmission trouble shows up as one of four things. Note which one you have before you call.

A tachometer needle high in the rev range with a warning light lit

Revs climb, the car doesn't speed up

That is slipping. The engine is spinning but the power isn't reaching the wheels. It often starts on hills or when merging.

An automatic gear selector showing P, R, N and D

A clunk, or a long pause, going into gear

Shifting into Drive or Reverse should take about a second. A thump or a two-second wait points to pressure, fluid or a control problem.

An instrument cluster with several amber warning lights lit

A warning light, and it stays in one gear

Many cars protect a failing transmission by locking it in one gear. It feels gutless and revs high on the highway. The stored code is the first clue.

A hand reaching up to the underside of a car near the transmission

Red drips, or a burnt smell

Transmission fluid is usually red. A spot under the middle of the car, or a smell like scorched toast after a drive, needs looking at soon.

If it's slipping badly, park it.

Slipping makes heat, and heat wears out more parts. Every extra mile can turn a smaller repair into a bigger one. A tow is often the cheaper choice.

A mechanic holding a handheld diagnostic scan tool — A scan tool reads the codes the transmission computer stored when something went wrong.

Not every shifting problem is a rebuild

Low fluid, a failed sensor or solenoid, a wiring fault or a software update can all make a car shift badly. Those are smaller jobs than a rebuild.

The only way to know is to check: read the codes, look at the fluid, and drive the car. Ask for what was found, in plain words, and the price before you approve work.

Useful to mention when you call

Year, make, model and rough mileage
When it started, and whether it was sudden
Worse cold, or worse once warmed up
Any warning lights on the dash
Whether it still drives, or needs a tow

A fuel gauge and odometer reading 147,253 miles — Mileage and service history change what's likely.

Close view of a stack of transmission gears

An automatic shifter in a car's centre console

Diagnostics, rebuilds and clutches

Diagnostics

Finding the actual fault comes before any parts. That means codes, a fluid check, a test drive, and a look underneath for leaks and damaged mounts or lines.

A mechanic standing under a raised car inspecting the drivetrain

A cutaway automatic transmission showing its clutch packs and gearsets — A cutaway shows what a rebuild opens up: clutch packs, gearsets, seals and the valve body.

Rebuilds

When the inside is worn, the transmission comes out and gets taken apart. Worn clutches, seals and other wear parts are replaced, then it goes back in and gets road tested.

Metal drivetrain parts laid out on a grid

The automatic gear selector in a pickup truck

Clutches

On a manual, a worn clutch shows up as revs rising in higher gears, a pedal that only bites near the top, or grinding going into gear.

Catching it early can keep the flywheel from needing replacement too.

Check the fluid colour first

If your car has a transmission dipstick, check it with the engine running and warm, on level ground; the owner's manual says which gear. Wipe it on a white paper towel.

Bright red, see-throughNormal.

Dark red or brownOld fluid. Worth having checked.

Near black, smells burntIt has overheated. Call before driving far.

Pink and milkyCoolant may be mixing in. Stop driving it.

Many newer cars have no dipstick, and some fluids are not red to begin with. If yours is sealed, leave it and mention that when you call.