Automatic gearbox specialists
Having a torque converter lock-up issue?
Shudder at 40 to 60, a flare when lock-up should hold, or a code for the clutch. It will not polish out.
- A shake at cruise that eases if you lift or tap Neutral?
- Lock-up clutch code on the scan?
- Told you need a gearbox when the converter may be the job?
Lock-up is a clutch inside the torque converter that locks engine to gearbox at cruise. When it judders or slips, you feel a shake. Lock-up diagnosis is core automatic work at Service4Service.
Lock-up shudder is not a wheel balance. Keep driving it and you glaze the clutch and burn the fluid.
8am - 5.30pm Mon-Fri
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What is torque converter lock-up?
Inside a torque converter a lock-up clutch can bolt the engine to the gearbox so fluid slip stops wasting fuel. The transmission control unit applies it via a solenoid in the valve body.
It is a feature of a conventional automatic gearbox, not a dual-clutch. Dual-clutch cars do not lock up a converter they do not have.
Shudder here is often mixed up with judder from clutch packs. A diagnostic check splits them.
Lock-up shudder will not bed in
A shake at steady speed that eases when you lift is the lock-up clutch slipping. Heat glazes it. Leave it and a converter job can become a fluid-and-valve-body mess as well.
Lock-up symptoms people search
If any of these sound like your car, do not wait for it to fail on the road.
Shudder at cruise
Classic lock-up clutch.
Eases in Neutral or when you lift
The clutch has opened. That is your clue.
Flare when it should hold
The clutch is not staying applied.
Worse when hot
Fluid and friction fade.
Lock-up solenoid code
Valve, wiring or the clutch.
Higher revs at cruise than before
Lock-up is not staying on.
How lock-up works
At speed the TCU commands lock-up. Oil applies the clutch in the converter. Wrong automatic transmission fluid or a sticking valve makes it chatter.
After converter work the unit may need adaptation.
Cruise speed arrives
The TCU commands lock-up.
The clutch in the converter closes
Slip should stop.
A glazed clutch chatters
Shudder, then heat. It only gets worse.
Lock-up work we do
We diagnose shudder versus engine, mounts and dual-clutch packs, then repair the converter, the valve or the fluid circuit if lock-up is the fault.
- Cruise shudder diagnosis
- Converter and lock-up clutch repair
- Solenoid and fluid checks
- Collection when it should not be driven
Still shaking at cruise?
If it eases when you lift, think lock-up. That is automatic gearbox repair. Call before the converter is cooked.
Why this work comes to Service4Service
- Automatic and dual-clutch work is core work, not a sideline
- Diagnosis before parts
- Collection when the car should not be driven
- 12 months or 12,000 miles on parts and labour
Guarantee and payment
Repairs are backed by a 12 month or 12,000 mile warranty on parts and labour. See Payment Options for ways to pay.
No. It is a clutch inside the converter, applied by oil, with no pedal.
Sometimes a correct-spec change helps a mild case. A glazed clutch needs the converter.
Some CVTs have a converter with lock-up as well as pulleys. Diagnose the car you have.
That is often when lock-up is commanded.
No.
No. That is the clutch in the converter slipping under load.
Related guides
Do not balance the wheels for a lock-up shudder
If cruise shakes and lifting eases it, tell us. Lock-up diagnosis is work we do every day.
