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Clutch Replacement on the Porsche 911 Carrera
 
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Pelican Technical Article:

Clutch Replacement on the Porsche 911 Carrera

Time:

12 hours12 hrs

Tab:

$750

Talent:

****

Tools:

Torx socket set, clutch alignment tool, flywheel lock, torque wrench

Applicable Models:

Porsche 996 Carrera models (1999-05)
Porsche 996 Turbo, GT2, GT3 (2001-05)
Porsche 997 Carrera models (2005-12)
Porsche 997 Turbo, GT2, GT3 (2007-13)

Parts Required:

Complete clutch kit

Hot Tip:

Purchase a kit with everything in it, not some simple version

Performance Gain:

Smoother shifting, no power loss

Complementary Modification:

Replace intermediate shaft bearing, install lightweight flywheel

One of the most common repair procedures for the manual transmission 911 Carrera is the replacement of the clutch assembly. Unfortunately, it is a rather big process involving the removal of the transmission. The good news is that it's really not a super-difficult job if you have some information and a few hints and tips.

How do you know if your clutch is beginning to fail? There are a few ways to tell. First, you should figure out how old your current clutch is. If your car is driven with mostly highway miles, then clutches can last almost forever. However, if you often drive around town somewhat aggressively, then you will probably have to replace your clutch at about 30,000 miles or so. With a hydraulic clutch system like the one on the 911, it can be a bit more difficult to determine the exact problem than with an older-style cable clutch system. Spongy pedals, excessive free play, and grinding noises all indicate problems with the clutch or hydraulic system. Strange noises that change when you push in the clutch pedal can indicate a pilot bearing or throw-out bearing beginning to fail. Finally, if your clutch begins to slip when the pedal is not depressed, then chances are your clutch disc is worn or the spring plates in your pressure plate have worn out.

The first step is to remove your transmission from the car. See Project 37 for detailed instructions on this procedure. Once the transmission has been removed, you will want to remove the pressure plate. On this particular car, I found that some of the pressure plate bolts had problems rounding out when I went to remove them. If this happens, then dig out your trusty Dremmel tool and cut them off in about 1 minute. Don't waste your time trying vice grips or other foolish methods--you can cut them off, and you don't need to worry about damaging the pressure plate because you're going to be replacing it anyways. When you're ready to remove the last bolt, grab the pressure plate with one hand--it's easy for it to fall off when the last bolt is removed. The disc should also pop out when you remove the pressure plate.

With the pressure plate removed, you should be able to see the flywheel. The 911 Carrera uses a dual-mass flywheel, which is a two-piece component that is bonded together. This changes the natural frequency of the flywheel and reduces vibrations in the engine. Unfortunately, this flywheel can be expensive to replace. Porsche has released a Technical Service Bulletin on checking the dual-mass flywheel (TSB 911 8/02 1360), which I have placed on the 101Projects.com website for reference. Basically, the test procedure is to twist the pressure plate surface of the flywheel about 15mm to both the left and the right and check to see if it returns to approximately its original position. If the flywheel cannot be twisted at all, or if the flywheel can be twisted beyond the 15mm without a noticeable increase in the spring force, then the flywheel is likely to be faulty. Typically it's a wise idea to replace your dual-mass flywheel every 100,000 miles or every other clutch replacement.

The next step here is to remove the flywheel bolts. You can use a socket and breaker bar along with your flywheel lock. With the bolts removed, your flywheel should be able to be tugged off of the crankshaft.

At this point, you'll want to turn your attention to the transmission and refurbish the throw-out bearing and arm. Start with the throw-out bearing guide tube. This is the small tube that the throw-out bearing rides on when the clutch is disengaged. As the throw-out bearing slides back and forth on the tube, the tube has a tendency to wear out. Remove the bolts that hold the guide tube to the transmission. Remove the guide tube, and inside you will find the mainshaft seal. Using a small screwdriver, punch a small hole in one of the indents in the surface of the seal, and pick out the old seal and remove it (see Figure 5). Clean out the inside of the bore where the seal fits, and install the new one. Tap it in lightly with the end of a socket extension, taking care to make sure it doesn't go in half-cocked. Install the seal so that it is flush with the flange. Now install the new throw-out bearing guide tube. Although the factory manuals state to install the guide tube without any grease, I like to apply a light coat of white lithium grease to help things along. Check the small retainer clip, the pivot pins, and the throw-out arm pivot piece (see Figure 6). Lubricate the two pivots with white lithium grease. Take the new throw-out bearing, snap it on the throw-out arm, and attach the arm to the transmission. Your throw-out arm is now ready for assembly back into the car.

Now would also be an excellent time to replace your intermediate shaft bearing. This bearing has been responsible for more than its share of Carrera engine failures over the years and access is easy with the clutch removed (see Pelican Technical Article: IMS Bearing Replacement - Porsche 911 Carrera).

Now, it's time to turn our attention back to the flywheel end of the engine. Porsche Tech Bulletin 8/02 1360 says to check the dual-mass flywheel by twisting it approximately 15mm to both the left and the right, checking to make sure that it returns to its approximate starting position. If the flywheel can be twisted beyond about 15mm with no noticeable increase in spring force or if it cannot be twisted at all, then it probably needs replacement. If the flywheel checks out okay, then replace the flywheel pilot bearing and the flywheel seal as shown in Figure 9 and Photo 10.

Now you're ready to reinstall the flywheel onto the engine. Always use new flywheel bolts, as they are only meant to be tightened and stretched once. Install your new or reconditioned flywheel onto the engine, then install the new flywheel bolts and torque them down. You must use a torque wrench and a flywheel lock to tighten the flywheel (See Photo 11 and Photo 12).

With the flywheel mounted, now take your clutch alignment tool and place it in the center of the pilot bearing. Install the clutch disc onto the flywheel (see Photo 13). Then install the pressure plate onto the flywheel, compressing the clutch disc. Use new pressure plate bolts to keep everything fresh. When the pressure plate is tightened down to its proper torque, remove the alignment tool. The disc, pilot bearing, and pressure plate should all be aligned (Photo 14).

Reinstall your transmission as per the instructions in Pelican Technical Article: Transmission Removal - Porsche 911 Carrera. Reattach your slave cylinder, the backup lamp switch, and the driveshafts. At this time, I also recommend that you bleed your clutch system (see Pelican Technical Article: Replacing Clutch Hydraulics on the Porsche 911 Carrera).

I wish I could say this was an easy job, but it's not. It's not impossible, but there's a lot of stuff to remove and a lot of tricky spots. One of the things that you want to do is purchase a complete kit that contains everything that you need for the job--all of the nuts, bolts, and bushings, as this will be a huge timesaver. The only place that currently sells such a kit is PelicanParts.com.

Lightweight Flywheel: While reducing this weight will not buy you any more horsepower, it can increase your engine's response and acceleration. The reasoning behind this is that the rotational mass of the engine takes time to "spin up" when you accelerate. Decreasing the rotational mass of the engine allows for quicker response times when accelerating. This is because more energy from the engine is being used to accelerate the mass of the car, instead of accelerating the mass of the engine components. In addition, reducing the mass of rotating engine components has a two-fold result on performance, you not only make the engine quicker, but you are also reducing the total weight of the car. This is discussed further in this book under "Weight Reduction" in Pelican Technical Article: Track Prep for the Porsche 911 Carrera. The flywheel and other rotational components serve to raise the rotational or angular momentum of the engine so that the engine will continue to rotate smoothly until the next compression stroke. Adding a lightweight flywheel/components allows you to adjust engine rpm's much quicker. However, it will also drop down in rpm much quicker as well when you let off of the throttle. This often makes the car difficult to drive on the street in day-to-day traffic conditions. Also be sure to only use a spring-centered clutch disc with a non-dual-mass flywheel (see Figure 5).

Here's what your engine will look like after you have removed your transmission.
Figure 1

Here's what your engine will look like after you have removed your transmission. Shown here is the pressure plate (blue arrow). There is a jack stand underneath the engine supporting the weight that is normally supported by the transmission.

Attach your flywheel lock (see Photo 11) and constrain the flywheel in position as you remove the flywheel bolts.
Figure 2

Attach your flywheel lock (see Photo 11) and constrain the flywheel in position as you remove the flywheel bolts. With the flywheel off, remove the flywheel seal underneath. Using a screwdriver, puncture and remove the seal. Be careful not to damage any of the side surfaces where the seal mates to the engine case.

The first step is to make sure that you gather all the required parts for the job before you begin.
Figure 3

The first step is to make sure that you gather all the required parts for the job before you begin. It is very frustrating to get halfway through a replacement job only to find out that you need a part or a tool that you don't have. Here is photo of the PelicanParts.com clutch SuperKit that contains a comprehensive set of clutch replacement parts for a Carrera Ring Gear (for demonstration purposes, already installed on flywheel) Dual Mass Flywheel Flywheel Bolts Clutch Sealing Ring Input Shaft Seal Throw Out Bearing Clutch Release Lever Pivot Ball Pin Pressure Plate Bolts Throw Out Arm Pivot Piece Retaining Spring for Pivot Piece Throw Out Bearing Guide Tube Pilot Bearing (for demonstration purposes, already installed) Engine Flywheel Seal Pressure Plate Clutch Disc

Shown here is a lightened flywheel.
Figure 4

Shown here is a lightened flywheel. The main advantage to using the lighter-weight flywheel is that it reduces the weight of the rotational elements in the engine. However, the installation of the lightened flywheel may make the car difficult to drive, particularly in traffic. In addition, if you install a lightened flywheel, make sure you install a spring clutch disc along with it (inset photo). Don't use the stock clutch disc. If you use the stock disc there will be nothing to absorb driveline shock and vibrations, and you might damage your engine and/or cause the engine to trigger false misfire faults.

This photo shows the transmission mainshaft with the throw out bearing guide attached (blue arrow) and the pivot ball pin (red arrow).
Figure 5

This photo shows the transmission mainshaft with the throw out bearing guide attached (blue arrow) and the pivot ball pin (red arrow). Pluck the old seal out of the transmission bore and tap in a new one Insert of guide and seal.

The throw-out fork (inset) is attached at one end with a small metal clip (yellow arrow).
Figure 6

The throw-out fork (inset) is attached at one end with a small metal clip (yellow arrow). Remove the fork from the transmission by pulling out on the fork and unhooking the clip from its catch on the bottom. Clean the entire assembly and then lubricate everything with white lithium grease, including the throw-out bearing guide tube (green arrow). Make sure that the parts are assembled correctly, as per the photo. The throw-out bearing clips onto the throw-out arm as shown in the inset photo. Pay special attention to the orientation of the pivot piece and pin (red arrow).

If your backup lamp switch is giving you trouble, now is the perfect time to replace it.
Figure 7

If your backup lamp switch is giving you trouble, now is the perfect time to replace it. The switch is located on the end of the transmission near the rubber mount. Replacement is as simple as removing it from the top of the transmission case (blue arrow).

Shown here is the infamous intermediate shaft bearing that is responsible for so many engine failures on both the Boxster and the 996.
Figure 8

Shown here is the infamous intermediate shaft bearing that is responsible for so many engine failures on both the Boxster and the 996. Recent advances from crafty engineers in the aftermarket have developed a solution to remove and repair this bearing while performing a clutch replacement. To ignore this bearing while performing your clutch replacement is somewhat foolhardyâÂÂ"the majority of engines that have blown up in recent years have been attributed to the failure of this bearing. For more information, see Pelican Technical Article: IMS Bearing Replacement - Porsche 911 Carrera.

The pilot bearing holds the transmission input shaft in place and aligns the transmission up with the crankshaft.
Figure 9

The pilot bearing holds the transmission input shaft in place and aligns the transmission up with the crankshaft. B: To remove the flywheel pilot bearing, use an appropriately sized socket and gently tap with a hammer. C: The new bearing should fit easily inside the hole in the crankshaft. D: Use a deep socket to evenly tap in the bearing so it's flush with the surface of the flywheel (inset).

Take your new flywheel seal and coat it with a light touch of Curil-T.
Figure 10

Take your new flywheel seal and coat it with a light touch of Curil-T. Then install it onto the engine, taping lightly around the edge. The newer-style seal is supposed to be seated about 14mm or so below the end of the crankshaft. This means that the seal will sit about 3mm or so recessed beyond the edge of the case (yellow arrow). There is a special Porsche tool designed for the installation of this seal, but I simply made my own using some plastic pipe from the local hardware store that was the same diameter of the seal. Tap lightly and carefullyâÂÂ"make sure that the seal doesn't become cocked in its bore. Clean up any leftover sealant that squeezes out.

I use a simple flywheel lock that is basically a strip of metal with two large slots in it (arrow, right).
Figure 11

I use a simple flywheel lock that is basically a strip of metal with two large slots in it (arrow, right). This allows you to attach the lock to a bolt affixed to the engine case, and one affixed to the flywheel, where the pressure plate bolts normally mount. This inexpensive lock works great on almost any car. With the lock in place, torque the bolts, working in a crisscross pattern. When tightening the flywheel fasteners, use the manufacturer supplied torque specifications and follow the tightening sequence and steps precisely. The fasteners are torque to yield and require a multi-step tightening process. 

Shown here is a simply degree wheel that I made for tightening flywheel bolts.
Figure 12

Shown here is a simply degree wheel that I made for tightening flywheel bolts. Download and print out the wheel on a thick piece of paper. Then, get some 3M tack adhesive and spray the back, so it sticks to the flywheel like a Post-It note. Then, crank each bolt 120 degrees clockwise to achieve the proper tightness/stretch of the flywheel bolts. You can download and print out the template of the degree wheel from the 101Projects.com website.

The clutch alignment tool (green arrow) is used to align the clutch disc (red arrow) with the pilot bearing, pressure plate, and flywheel (blue arrow).
Figure 13

The clutch alignment tool (green arrow) is used to align the clutch disc (red arrow) with the pilot bearing, pressure plate, and flywheel (blue arrow).

Without the alignment tool (blue arrow), it would be nearly impossible to insert the transmission input shaft into the pilot bearing when mating the engine and the transmission back together.
Figure 14

Without the alignment tool (blue arrow), it would be nearly impossible to insert the transmission input shaft into the pilot bearing when mating the engine and the transmission back together. When the pressure plate bolts are all tightened down, you should be able to easily pull out the alignment tool, and the pressure plate and clutch disc should be centered with respect to the pilot bearing (photo inset). I recommend using new pressure plate bolts when performing a clutch replacement project.

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Comments and Suggestions:
Redlineman Comments: Those of you doing this job should first pull it apart to verify exactly which clutch you have. There were various different types of parts used in the mid years, between both 996s and Boxsters, and you may run into compatibility issues. So far I know of at least two different pressure plates - short and long fingered. There are other pieces that must also be different, but I have not been able to find out what they are. The latest parts diagrams do NOT offer much help either. Just be prepared before you order!!
May 12, 2016
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
np Comments: Could you please clarify the procedure for tightening flywheel to crankcase bolts. At Figure 11 it states: “Start by tightening all the bolts to 50 percent of their final value, and then go around again and tighten them to the final value. Than crank them another 90 degrees… what is the final value?. At Figure 12 it states: “ Than, crank each bolt 120 degrees clockwise to achieve proper tightness/stretch of the flywheel bolts.”
Does it mean to tighten to final torque value ??Nm, then another 90 degrees, then yet another 120 degrees? Or something different. Thanks!
January 12, 2016
  Followup from the Pelican Staff:
I believe the torque spec is not included due to difference specs for different engine or flywheel types.

I don’t have that info.

I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 
ron Comments: I just replaced my clutch with a litewt flywheel and a sprung pressure plte . Th pivot ball was longer than the oringinal but it was the only one plican had. Now the shift level can shift w the engine off but when I I depress the clutch pedal w the engine on the shifter will not shift . What did I do wrong.
December 1, 2015
  Followup from the Pelican Staff: You may have installed the incorrect pivot. I would double check if the part number is for your vehicle. - Nick at Pelican Parts  
John Comments: Hey Nick, I was just wondering; is there a way to take off the pilot bearing without taking off the flywheel? Thanks!
July 29, 2015
  Followup from the Pelican Staff: Yes, there are small slide hammers with expanding jaws that can extract it. - Nick at Pelican Parts  
Steve Comments: We replaced a clutch on a 2002 996 Awd with a single mass clutch set up.
Everything works except the transmission has a rumbling sound when idling in neutral, when the clutch is pressed the sound goes away.
Any thoughts, is this normal?
April 21, 2015
  Followup from the Pelican Staff: No, there should be no sound. Likely a bearing or faulty pressure plate. Does clutch performance feel normal? - Nick at Pelican Parts  
Jager Comments: Hey Nick... What is the flywheel bolt torque on the M96 manual gearbox?
February 16, 2015
  Followup from the Pelican Staff: flywheel to crankcase: initial torque 25Nm, then rotate additional 90°. Use new fasteners. - Nick at Pelican Parts  
Dave Comments: What is the guide tube's seal part number? Does it come with the guide tube?
November 25, 2014
  Followup from the Pelican Staff: I am not great with part numbers. Give our parts specialists a call at 1-888-280-7799. They can help you find the right part.
- Nick at Pelican Parts
 
PorscheC4S Comments: What is the "magic number" - offset of the flywheel flange from the mounting face of the bell housing for the dual mass flywheel?
August 19, 2014
  Followup from the Pelican Staff: I am not sure what you are asking. What are you trying to fix? - Nick at Pelican Parts  
Ed M Comments: Thanks Nick! I thought the article on clutch replacement should mention that. Excellent article BTW. It sure makes the job sound doable and leaving the engine in place sure makes it easier.
September 12, 2013
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help. - Nick at Pelican Parts  
Ed Machen Comments: Why not replace the engine/flywheel rear main seal as well as the transmission shaft seal?
September 11, 2013
  Followup from the Pelican Staff: I tend to lean toward replacing the rear main sela when replacing the IMS bearing. While you're in there get it out of the way, this way you don't have to go back in when and if it leaks. - Nick at Pelican Parts  

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