Throwout Bearing vs Hydraulic Release Bearing: Why Replace It With the Clutch

Throwout Bearing vs Hydraulic Release Bearing: Why Replace It With the Clutch

Throwout Bearing vs Hydraulic Release Bearing: Why Replace It With the Clutch

A throwout bearing and a hydraulic release bearing do the same job: they push on the pressure plate fingers so the clutch lets go when you press the pedal. The difference is how they are moved. A conventional throwout bearing rides on a fork that a linkage or external slave cylinder pushes. A hydraulic release bearing, often called a concentric slave cylinder (CSC), has the hydraulic piston and the bearing in a single unit that sits around the transmission input shaft. Either way, the answer to the title question is the same: replace it with the clutch, because you cannot reach it without removing the transmission.

Shop the parts in this guide

Hydraulic release bearings and slave cylinders for specific Mustang and Wrangler applications, plus a clutch kit to pair with them. Each listing names its vehicle in the title.

Browse more: Clutch hydraulics | Bearings and install kits | Clutch kits

How the two designs differ

  • Mechanical throwout bearing: a bearing on a carrier that a release fork pushes. The fork is moved by a cable, a rod linkage, or a separate slave cylinder bolted to the bellhousing.
  • Hydraulic release bearing (CSC): the slave cylinder is built into the bearing itself. Pedal pressure pushes fluid from the master cylinder into the unit and the bearing moves directly against the pressure plate. The McLeod 1220 listing describes the part as a direct replacement for the factory throwout bearing, also known as a concentric slave cylinder (Steeda product page).

The practical consequence: on a hydraulic release bearing, a worn bearing and a leaking slave cylinder are the same part, so one failure takes out both functions.

Symptoms of a failing release bearing

One repair guide lists the common signs of a bad throw-out bearing: a rattling or noise when the pedal is pressed, vibration in the pedal, difficulty shifting, a stiffer pedal as lubrication degrades, and grinding after the clutch is fully depressed (MechanicBase). On a hydraulic unit, add a pedal that sinks, a pedal that does not fully release the clutch, or fluid loss. Those hydraulic symptoms point at the slave and its seals.

Why it gets replaced with the clutch, not after

There are two separate reasons.

1. Labor. The bearing is hidden behind the transmission. MechanicBase notes that the part is a minor expense and that the bulk of the cost is labor, which is why it recommends replacing the clutch, pressure plate and pilot bushing at the same time rather than paying for the teardown twice.

2. The bearing wears against the new parts. The release bearing runs against the pressure plate fingers on every pedal press. A worn bearing on a new plate wears both. Schaeffler's guidance, relayed by PMM Online, calls replacing the concentric slave cylinder with the clutch best practice, notes that the release bearing assembly should always be replaced with a new clutch, and points out that if a CSC fails after the repair, the leaking fluid contaminates the newly installed clutch and the gearbox has to come out again (PMM Online). The same article notes that the guide tube can be contaminated, worn or corroded, and the rubber seal can be contaminated with old fluid, so flushing and refilling per the manufacturer's specification is part of the job.

McLeod 18-24 Ford Mustang GT / 15-20 Ford Mustang GT350 1220 Series Hydraulic Throwout Bearing
McLeod 18-24 Ford Mustang GT / 15-20 Ford Mustang GT350 1220 Series Hydraulic Throwout Bearing

Which one do you have?

Look at the vehicle. If there is a fork and a pivot visible through the bellhousing, or a slave cylinder bolted to the outside of the bell, you have a conventional throwout bearing. If a hydraulic line runs straight into the bellhousing with no fork, it is a CSC. The hydraulic units we list are for specific vehicles; the listings above state the vehicle in the title, so match yours before ordering.

Pedal feel and the bearing

If you are changing clutches for more holding power, the release system matters for pedal effort. MotoIQ's clutch series lists a smaller throwout bearing and a larger-bore slave cylinder among the ways designers cut pedal effort, with the tradeoff that a larger bore can slow clutch release by a few milliseconds (MotoIQ). We cover the heavy-pedal question in detail in a separate guide.

Replace-while-you-are-in-there list

Cost and effort framing

The McLeod 1220 listing rates installation as moderate and about 7 hours with basic shop tools, and says it works with factory and aftermarket clutches (Steeda). Do the clutch and release bearing in the same sitting and the extra time is small. Do them in two sittings and you repeat the entire job.

Ready to order? McLeod 18-24 Ford Mustang GT / 15-20 Ford Mustang GT350 1220 Series Hydraulic Throwout Bearing; Exedy 11-15 Ford Mustang GT V8-5.0L Slave Cylinder / Release Bearing - BRG0186; McLeod 2007-11 Jeep Wrangler 3.8L / 2012-18 Wrangler 3.6L 1200 Series Hydraulic Throwout Bearings - 1250.

Related: Jeep Wrangler clutch replacement kit guide.

Frequently Asked Questions

Can I replace just the hydraulic release bearing and keep the old clutch?

You can, but the transmission has to come out either way, so most people replace the clutch at the same time. If the old clutch is worn, you will repeat the job soon after.

Is a concentric slave cylinder the same as a hydraulic throwout bearing?

Yes. Both names describe the single unit that combines the slave cylinder and the release bearing.

Do I need to bleed the system after installing a new one?

Yes. A new hydraulic unit needs the system bled and the fluid level set per the vehicle manufacturer's instructions. PMM Online's summary of the Schaeffler guidance notes flushing and refilling to specification.

Sources