Clutch Slave Cylinders

What Does a Clutch Slave Cylinder Do?

A clutch slave cylinder moves the clutch fork or release bearing so your clutch disengages when you press the pedal. The pedal operates the clutch master cylinder, which sends fluid through a line to the slave cylinder. That pressure drives a piston, and the piston moves the release mechanism so the pressure plate lets go of the clutch disc.

Because the system is hydraulic, the slave cylinder only works as well as the parts feeding it. A worn master cylinder can feel like a slave cylinder problem, so inspect the whole circuit before you buy. If the master is suspect, compare replacement clutch master cylinders at the same time.

The slave cylinder also controls how far the release bearing travels. Too little travel leaves the clutch dragging, which makes gear changes hard. If you're replacing the clutch too, match the disc and pressure plate from our clutches and clutch kits category.

How Do External and Concentric Slave Cylinders Differ?

An external slave cylinder bolts outside the bellhousing, while a concentric slave cylinder mounts inside it around the transmission input shaft. That location changes how you service it and how much labor a replacement takes.

Here's how the two designs compare:

• An external slave cylinder uses a piston to push or pull the release fork.
• You can usually replace an external unit without removing the transmission.
• A concentric, or internal, slave cylinder combines the cylinder and release bearing in one part.
• Replacing a concentric unit usually means pulling the transmission.

Concentric units are also called hydraulic throwout bearings, and they do away with the fork and pivot. If your car uses one, or you're converting to one, compare options alongside our clutch release bearings. Since reaching one takes so much labor, it makes sense to replace a concentric unit whenever the transmission is already out.

How Do You Match Slave Cylinder Type and Bore Size?

Match the slave cylinder to your transmission's release design first, then match its bore to the master cylinder. A push-type slave cylinder pushes the release fork, while a pull-type slave cylinder pulls it. Pull-type units show up in racing setups and some street applications.

For example, McLeod offers a pull-style aluminum external slave cylinder with a 0.625 in. bore for 1979-2004 Ford Mustang. McLeod also offers an anodized aluminum external unit with a 0.875 in. bore for 1993-1997 Chevy Camaro and Pontiac Firebird.

Slave cylinder bore size works with master cylinder bore to set pedal effort and release travel. Change either bore and you change the ratio, which shifts pedal feel and how far the bearing moves. Some hydraulic release bearing kits require a 0.750 in. bore master cylinder, so check the instructions before you order.

To narrow the list, use the Part Type, Outlet Size, Body Type, and Material filters. Then add your vehicle to confirm fit.

Which Slave Cylinder Kits and Conversion Kits Fit Your Build?

A hydraulic clutch conversion kit replaces a mechanical clutch linkage, while a direct-replacement slave cylinder restores a factory hydraulic system. McLeod direct-fit conversion firewall assemblies for Ford Mustang include everything except the slave cylinder. That lets you choose a slave cylinder that matches your transmission.

For repairs on factory hydraulic systems, you can pick from these options:

• Dorman Products direct-replacement slave cylinders for 1983-1997 Ford, 1991-1996 Corvette, 1984-1991 Chevrolet/GMC, and 1985-1987 Toyota Corolla
• Crown Automotive slave cylinders for 1983-1986, 1984-1993, 1987-1992, 1993, and 2007-2018 Jeep models
• Crown Automotive clutch slave cylinder repair kits and hydraulic clutch actuators
• Slave cylinders for 1995-2004 Toyota Tacoma V6 and 1998-2002 Chevy Camaro V8

Whatever you choose, inspect the fluid line and hardware that connect the master and slave. Plan on new clutch hydraulic lines and linkage if the old line is cracked, kinked, or the wrong length for a conversion.

What Are the Signs of a Bad Clutch Slave Cylinder?

A bad clutch slave cylinder usually shows up as a soft pedal, a fluid leak, or a clutch that won't fully release. Worn internal seals let fluid slip past the piston, so pressure never builds the way it should.

Watch for these bad slave cylinder symptoms:

• Soft or spongy pedal feel
• Fluid on the slave cylinder body, bellhousing, or floor below
• Clutch that won't fully disengage with the pedal down
• Hard shifting or grinding when you select a gear

Before you replace parts, check the fluid level and condition with our guide on how to check and change hydraulic clutch fluid. If the fluid is full and clean but the symptoms stay, the seals are likely worn and the slave cylinder needs replacing. When you're ready, add your vehicle on this page to see the slave cylinders that fit.