A stall converter is a torque converter designed to let the engine reach a higher rpm before the vehicle moves. Stall speed is the engine rpm the converter allows, in gear with the brakes held, before it transmits enough torque to move the vehicle against the brakes. A higher-stall converter lets an engine with an aggressive cam or a power band higher in the rpm range launch closer to where it makes its power.
What is torque converter stall speed?
A torque converter connects the engine to an automatic transmission through fluid rather than a mechanical clutch. The impeller, turned by the engine, drives fluid against the turbine, which turns the transmission input shaft, while the stator between them redirects fluid to multiply torque at low speed. At idle in gear, the converter slips enough for the vehicle to sit still with light brake pressure. As engine rpm rises, it transmits more torque until it moves the vehicle. Our guide to bad torque converter symptoms explains what a torque converter does in more detail.
You will see two terms used:
- Brake stall: the rpm the engine reaches at full throttle with the transmission in gear and the brakes held. A brake-stall test builds heat in the fluid very quickly, so follow service information and keep it brief.
- Flash stall: the rpm the engine flashes to when you launch from a stop at full throttle. It is affected by vehicle weight and gearing as well as the converter.
Why use a higher-stall converter?
A factory converter is matched to a factory engine that makes useful torque from low rpm. An engine with an aggressive camshaft, or one set up to make its power higher in the rpm range, may feel weak just above idle. A higher-stall converter lets the engine rev into its power band before the converter couples, which sharpens launch response. It can also make a big-cam engine easier to live with at idle, because a looser converter puts less load on the engine while it sits in gear at a stop.
What are the trade-offs of a stall converter?
- More slip and heat. A looser converter slips more before it couples, and slip turns into heat in the transmission fluid. A transmission cooler is commonly recommended, and our transmission fluid temperature guide explains why heat matters.
- Fuel economy. Extra slip at part throttle can cost fuel economy. Converters with a lockup clutch, as used with the 4L60E and 4L65E, can lock at cruise to reduce slip.
- Drivability. The vehicle can feel looser, with more engine rpm before it responds, which some drivers notice in traffic.
- Calibration. Lockup and shift behavior may need adjusting to suit the new converter and engine combination.
How do you choose a stall speed?
Matching a converter is about the whole combination: the engine’s torque curve and camshaft, rear axle gearing, tire size, vehicle weight and how the vehicle is used. A common approach is to pick a stall speed near the rpm where the engine starts making useful torque, and the camshaft maker’s recommended stall range is a sensible starting point.
Stated stall ranges also depend on engine torque. A converter’s advertised range assumes a certain amount of torque; behind an engine that makes more torque it will stall higher, and behind a milder engine it will stall lower. That is why stall is quoted as a range rather than a single number, and why a converter that suits one combination can feel quite different in another.
Our 4L60E and 4L65E billet converter
For LS-style engines backed by a 4L60E or 4L65E, we carry a Chevy LS-style 4L60E and 4L65E billet torque converter rated 2800-3200 stall. Confirm it suits your engine, camshaft and vehicle before ordering, and ask us if you are unsure. If you are replacing the whole transmission, our 4L60E transmissions page lists the complete units we carry, which are supplied with a torque converter.
More guides: torque converter lockup · torque converter replacement · how long a torque converter lasts · how much power a 4L60E can handle.
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