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Porsche 997: Why is My Transmission Noisy?

If you have a noisy transmission, then you might want to find out what is causing the noise before you consult a mechanic or start tearing apart the transmission on your own. This article explains three relatively common problems related to the transmission.

By Robert Olsson - May 14, 2015
Contributors: mjensen, 450knotOffice, Bill Wagner, rutz964C4

This article applies to the Porsche 997 (2005-2012).

It can be very challenging to listen to a transmission to troubleshoot the issue, especially if you have never heard the sounds before. However, there are a few diagnostics that you can use to get a rough idea of what a probable cause is. If you have a noisy transmission, then continue reading to find out some common problems with the Porsche 997 transmission.

Materials Needed

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Step 1 – Check the throw-out bearing

The throw-out bearing should be replaced when the clutch is replaced, and normally the bearing lasts at least as long as the clutch lasts. Therefore, under normal circumstances, the throw-out bearing shouldn't be an issue. However, it could, of course, wear out early.

To diagnose the throw-out bearing, with the engine running press the clutch to the floor. If you hear a much louder noise when you depress the clutch, then you probably have a bad throw-out bearing.

Figure 1. Really worn-out throw-out bearing inner race (the bearing has desintegrated).

Step 2 – Check the pinion bearing and carrier bearings

Do you have a whining noise that varies with the speed of your car? It might be the pinion or the transmission carrier bearings that are bad. Pinion bearing or transmission carrier bearings that are bad sound pretty similar, so it can be hard to distinguish between them. It begins with a very slight whining sound and progresses over time (several thousand miles) to become a deafening sound if not remedied.

It involves a lot more work to replace the pinion bearing compared to the carrier bearings, so you might consider replacing the carrier bearings before replacing the pinion bearings. On the other hand, pinion bearing failure seems a lot more common judging from the number of owners reporting trouble on the Internet.

Figure 2. Check the pinion bearing.

Step 3 – Check for a worn flywheel

The 997 is equipped with a dual mass flywheel. The flywheel basically consists of two thick metal sheets that are held together with rubber (or springs) between them. The flywheel is bolted on the outgoing axle from the engine, before the clutch (the clutch actually uses the flywheel to release the clutch plate against when the clutch is released). This means that the rubber works as a damper when the torque or revolution is changed on the driving shaft. This in turn saves the engine and the transmission since quick changes are dampened.

A worn-out flywheel usually produce a lot of noise. It could be everything from a rhythmic clacking sound that goes away when the clutch is pressed to a rattling sound like putting nails in a can and shaking it. The sound can also diminish a lot when the engine is warm.

Figure 3. Transmission flywheel.

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