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HomeTech Articles > Replacing and Adjusting the 914 Clutch - Page 3

Pelican Technical Article:

Replacing and Adjusting
the 914 Clutch

Page 3

Difficulty Level 6

Difficulty scale:
Adding air to your tires is level one
Rebuilding a 911 Motor is level ten

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Figure 33: Installing Flywheel O-ring

Figure 34: Installing Flywheel Pilot Bearing

Figure 35: Pilot Bearing Installed

Figure 36: Flywheel Placed on Crankshaft

Figure 37: Proper Assembly Order of Pilot Bearing, Felt Ring, and Washer

Figure 38: Flywheel Lock Installed, Flywheel Bolts Torqued

Figure 39: Disc Installed with Clutch Alignment Tool

Figure 40: Tightening Last Bolt on Pressure Plate

Figure 41: New Pressure Plate Installed

Figure 42: New Bushing Installed in Throw-Out Arm

Figure 43: Grease Shafts, Install New Throw-out Bearing

Figure 44: Reassemble Throw-out Fork Assembly

Figure 45: Check Transmission Fluid Level

Figure 46: Throw-out Pivot Ball

     Now you need to prepare your flywheel for installation.   Place the O-ring on the inside of the flywheel as shown in Figure 33. Also, remove the pressure plate guide pins from the old flywheel and place them on the new one.  Now, you need to install the pilot bearing.  These do not go in very easily, and there is no really good way of evenly pressing them in without an arbor press tool.  Place the bearing on the center of the back of the flywheel and gently tap it from above.  Nine times out of ten it will start to go in crooked.  If it is slightly crooked, then it will align itself as the tap on it.  If if is really crooked, then you may damage the bearing if you keep tapping on it.  Trial and error works best here.  Once you get the bearing started in its hole (Figure 34), finish tapping until the bearing is flush with the top surface, as shown in Figure 35.

     Now, place the flywheel on the crankshaft.  This shouldn't require any tapping with a hammer, just some careful placement.  There is a dowel pin on the crankshaft that needs to line up with a hole on the rear of the flywheel.   It will not go on any other way.  The flywheel should sit on the crank without falling off, as shown in Figure 36

     Now, place the felt pad and washer on the end of the flywheel and begin to screw in the new flywheel bolts.  Make sure that the felt pad is underneath the metal washer and is compressed by the torquing of the flywheel bolts.   The proper installation order of the felt ring and metal washer is shown in Figure 37.  After the bolts are finger tight, reattach the flywheel lock.  Make sure that it is tight and will keep the flywheel from turning clockwise.  Now, lightly tighten down the flywheel bolts.

     It has been suggested that if you have the proper tools, that the crankshaft end play be checked.  Most shops don't do this measurement, but an ounce of prevention is indeed worth a pound of cure.  You need a dial gauge that can be placed against the flywheel, while the base is mounted to the engine case.   Take the flywheel, and pull on it axially.  The end should be within the following limits: .07mm-.13mm.  Anything more or less, and you might have to add/subtract shims from the crankshaft end.

     Now, tighten down the flywheel bolts.  Work in a criss-cross pattern, and set the value on your torque wrench to something low, like 10 ft-lbs.  Keep increasing the torque and tightening the bolts in a criss-crossed pattern until you reach 79.5 ft-lbs.  This value is taken directly from the factory manual.  When the flywheel is fully attached, and the bolts tightened, it should resemble Figure 38.

     Once the flywheel is attached, remove the flywheel lock and place the new disc on the flywheel with the center knob pointing out towards the rear of the car.  Place the clutch alignment tool in the center of the flywheel and clutch disc.  Make sure that the tool is in tight, as shown in Figure 39.  Now, place the pressure plate on the flywheel, using the guide pins for alignment.  Place all the bolts except one in the flywheel and turn them so that they are finger tight.  Now, reattach the flywheel lock using the on free bolt hole.  Torque down the pressure plate screws in a criss-cross pattern using the same technique used to attach the flywheel.  After all the bolts are torqued to 14.5 ft-lbs, remove the flywheel lock and tighten the last bolt.  You can use a breaker bar to keep the flywheel from turning while you are torquing down the last bolt, as shown in Figure 40.  Pull out the alignment tool.  When you are finished, the installed pressure plate, disc and flywheel should resemble Figure 41.  Now it's time crawl out from underneath your car and focus your attention on the transmission.

    The first thing that you need to do on the transmission is remove the throw out arm from the transmission.  Loosen up the screw on the front of the arm and remove it off of the ball that holds it in place.  Make sure you capture the small fork that mounts to the rear of the fork.  Once you have the fork removed, inspect the throw out arm carefully, as these have a tendency to occasionally crack or bend.  Make sure that it is flat and not curved.  Also inspect the small fork that holds the arm to the ball on the transmission.  These often split or crack.   Now pry out the old bushing from inside the fork.  It may take some effort in order to fully remove the bushing.  Make sure that you remove all parts of it, as it has a tendency to break apart when you are trying to pry it out.  Install the new one by tapping it in with a small hammer.  The fork with the new bushing is shown in Figure 42.

     Now remove the throw-out bearing from the shaft of the transmission.  Place the new bearing on the transmission with the new guide clips installed on each end of the bearing.  Grease the shaft a bit before installing the throw-out bearing.  Figure 43 shows a new throw-out bearing (guide clips not yet installed) on the drive shaft.  Make sure that you place some grease on the tip of the shaft for the pilot bearing in the flywheel.   Now attach the throw-out arm and retighten the small fork that holds the arm to the ball on the transmission.  Make sure that the flat edge of the small fork is flat against the back of the throw-out arm when you retighten the arm.  Check the entire assembly (Figure 44) when you are done.   The throw-out bearing should ride smoothly on the shaft.

     Now, check the transmission fluid in the case.  You can do this by removing the fill cap on the side of the transmission as shown in Figure 45.  Top off the fluid (most likely it will be very low) until it begins to seep out of the top fill hole (the one that you removed).  Make sure that the transmission is on level ground when you do this.   Retighten the transmission fluid screw when you're done.

     After everything is checked, place the transmission on the jack and lift it up underneath the car.  Make sure that the driveshaft is level with the hole in the clutch disc.  The best way to align the transmission is to get one of the studs of the engine case started into one hole of the transmission case.   Then jack the car up until the stud on the other side is aligned with the hole on the transmission case.  Pushing the transmission forward should get it started into its proper position.  Once you have about and inch or so to go, you can lift and jiggle the tranny to get it closer.  I usually give it a kick or two on the rear cover with my sneaker to get it all of the way in. 

     Once the transmission is all of the way in, check the play on the clutch arm.  This is a very important step.  Ideally, there should be about a half inch of free play in the arm.  In other words, when the arm is resting on the transmission case (throw-out bearing all the way back towards the rear of the car), it should travel about half an inch before it hits the pressure plate.  If this travel distance is excessive, you need to shim the small ball that holds the throw-out fork.  This ball is shown in Figure 46.  Remove the ball using a socket and place a washer underneath it.  This of course, requires pulling the transmission back out from underneath the car (a pain in the butt).  However, if you don't check this and decide to instead fully reinstall the transmission, you may need to remove it from the car later on when you find that you can't release your clutch.

     If the free play is large, but you're not too sure whether it is too much, then you can perform a small test.  Tighten up the lower bolt on the left side of the transmission, and the upper bolt on the right side.  Then reconnect the clutch cable, and tighten it up so that you can release the clutch.   Put the car in gear and have a friend step on the clutch.  If you can turn the flanges on the transmission with the clutch pressed in, you're ok.  If not, then tighten your clutch cable until you can.  If you can't because the end of the arm is hitting the rear of the transmission case, you definitely need to shim the ball.

     Once you have checked to make sure that the clutch is ok, then it's time to begin reassembling.  Putting everything back together generally takes much less time than taking it apart because you've been there before, and there aren't any rusty parts to contend with.  Reattach all of the transmission case nuts and bolts.  Reattach the transmission to it's rear mounts.  Make sure that you check them to see if they are cracked - they usually are.  Now would be a great time to replace them, as they will help your shifting.  Reattach the starter, being careful not to drop that annoying nut into the engine compartment.  Reconnect the starter electrical cable and back-up switch.  Reattach the ground strap (important).   Reconnect the CV joints using new gaskets.  You may want to wait until the car is back on the ground to finally tighten all of the remaining bolts (just don't forget).   You also may want to put some more CV joint grease in there is you think that the joints need it.  Reattach the clutch cable if you haven't done it already.   Reconnect the speedometer cable and shift linkage, replacing the bushings if needed.   Reattach the accelerator cable if you have a 914-6.  Now replace the muffler using new gaskets, and making sure to reattach the  muffler bracket.

     Now, do a preliminary adjustment of the clutch so that the arm has just about no freeplay at the transmission case (the cable should be pulling the arm so that the throw-out bearing just rests against the pressure plate.  Lower the car, and then reattach the battery ground.  You should be able to drive the car out of your garage, and test out the clutch.  You can adjust the clutch feel by tightening the screw on the cable near the throw-out arm.  To make the clutch grab high on the clutch pedal, loosen the screw on the clutch cable.

     Well, there you have it.  Your clutch should perform well for another 30-60K miles depending upon your driving habits and style.   Remember, Pelican Parts depends upon your support through parts purchases to continue these tech articles and this web site.  If you have any questions or comments, please don't hesitate to ask.

James Thorusen adds his comments below:

I would agree that if you swap flywheels, you probably need to check the crank end float. There is no reason for it to change during a clutch job as long as you don’t change flywheels or machine the crank mating surface of the one you have.

The reason for the measurement is for the sake of the engine bearings.... the clutch does not care, within a wide tolerance, where it is on the input shaft, but the crank and rod journals, and pistons and rings, too, for that matter do care about crank end float. If, during the course of a clutch job, you change the crank end float by a significant amount, you will not have clutch problems, but you could have engine problems.

All in all, because of this tolerance, and for balancing considerations, it is best to always keep the crank and flywheel together as a unit, as long as it is possible to maintain the dimensions of the clutch surfaces within allowable factory dimensions for wear / resurfacing. If it becomes necessary to change flywheels, then the crank and flywheel should be sent together to a balancing shop for re-balancing, and the engine re-assembled with new bearings, and a fresh measurement / adjustment of crank end float.

I’m sure that that is not what you want to hear, since you are offering a flywheel exchange program, but I would never trade flywheels without re-balancing. You can probably get away with it most of the time on a stock street motor, since this is not a very high-reving engine, but in extreme cases, you can drastically shorten engine life and drivability.

I would like to take issue with one other point on your clutch relacement article: the note about the rear main seal. I would NEVER do a clutch job without replacing this seal. You have to take the flywheel off for pilot bearing and / or resurfacing anyway, and the seal is cheap insurance. The labor involved to replace it if it starts leaking a few thousand miles later is not worth the gamble, especially when you consider that if it develops a leak, it can ruin your new clutch disk, and if the oil-induced slipping is not detected and corrected promptly, the pressure plate and flywheel surfaces can suffer as well.... invalidating your entire clutch job.

No, don’t gamble... change that rear main seal (and the gearbox input shaft seal as well) EVERY time you replace the clutch.

Jim T.

Copyright Date of Origination by James K. Thorusen This material may be reproduced by anyone without charge or notification.

Norman Smith also has the following to add:

I just read the tech article on rebuilding the 911/914 pedal cluster. I found it very informative, and am in the process of using it as a guide to replacing the roll pins.

You might consider a short tech item referring to the pedal cluster rebuild regarding broken roll pins. I’ve had my 1974 911 since 1988, and am in the process of replacing the roll pin for the clutch for the third time. The first time this was done was in California in San Rafael at Sonnen Porsche. I thought the problem was with the cable or roll pin because I’d heard about problems with both these items. They examined the car and assured me that the problem was a collapsed pressure plate. I was unsure of this, but they insisted and I figured they ‘might’ know a bit more than me about the subject.

Well, after paying $800.00 to have the pressure plate replaced (it was two years old, and installed by Chris Powell in Bellevue WA) I drove back to my hotel in San Francisco where the car was parked in the garage for several days.

On Thursday we headed back home to Kirkland WA. When we got to the Golden Gate Bridge in rush hour traffic, the roll pin for the clutch pedal broke the rest of the way. It’s fortunate I’m able to shift without the clutch. When I got back to Sonnen Porsche, they said that ‘this was coincidental’. The roll pin broke because there was a new pressure plate. I said ‘yeah, right’ and spent six months trying to get my money back. I never did (need a used F&S ressure plate?)

The tip-off that the roll pin is going bad is that the clutch begins to shift hard, and improves when the cable is adjusted tighter. However, this only works for a few days, and must be done again. After about four times, the clutch pedal begins to feel funny, and then will drop to the floor when you try to depress it.

Shifting while moving after this is not too bad, but if you have to stop, you have to turn the engine off and start it again when the ‘light’ changes while in first gear. It starts right away and the car moves instantly, so be careful.

I think it is important that people be aware that the roll pin at $1.00 is probably a lot less expensive than having the pressure plate replaced. If the car begins to shift ‘hard’, and adjusting the clutch only corrects the problem for a short time, it’s probably the roll pin.

Norm Smith


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Comments and Suggestions:
Amphicar Comments: Questions regarding the washer under the pivot ball especially if flywheel refaced.

1. It is my understanding that the washer can be placed under the pivot ball after it is removed or else under the plastic cup that the ball sits in. Seems like same result either way. Is that correct?

2. I further understand that without the washer, you may find that the clutch is unable to disengage although you will only discover this once tranny is back in the car. Let's say you put the washer in and it is not needed. Is there any consequence or downside? If not, it would obviously make sense to err on the side of adding it.

Thanks for all the great articles.
April 17, 2016
  Followup from the Pelican Staff: 1. I am going by memory, but the washer goes between the pivot and the trans.

2. Correct. The washer left out will change clutch function. The height of the pivot is key, too long and clutch may not fully release, opposite for too short. - Nick at Pelican Parts
Amphicar Comments: A couple of things.

1. Checking the endplay is not difficult and is really important if you have refaced your flywheel. There are videos on YouTube that show how to do this.

2. Seems like replacing the main seal is a no-brainer and should always be done. Surprised this is not part of the kit.

3. The factory manual also specifies leaving 3.2mm space for the felt washer. This probably also insures the bearing seats properly at the engine side.

The felt washer is necessary. Per Mark Henry on one of the other 914 forums ....

The thing is the engine runs hot enough that the grease on the pilot bearing can melt, so without the felt washer it can leak past and contaminate your clutch disc.

The needle bearing should have grease packed into it and then a thin layer of a quality hi-heat grease on the surface. Like wheel bearings you do not fill the whole space with grease.

Also note the OP does have a new flywheel Oring installed, forgetting install a new flywheel O-ring is is also a common rookie mistake when replacing the main seal.
The Oring has a graphite coating do not clean this off before installation.
Also put a hair of grease on the main seal surface so the seal doesn't burn on start-up.
March 25, 2016
  Followup from the Pelican Staff: Thanks for sharing your installation process and experience. These type of comments add so much to the Pelican tech community.
- Nick at Pelican Parts
Jack Comments: I just remounted the flywheel and all the clutch parts on my 914 electric conversion. I opted to go with the Haynes manual method that sets the pilot bearing 3.2 mm back to make space for the felt washer. In the past I've had the bearing flush and left the felt washer out and that seems OK too. I think the felt washer is there to keep dust from the clutch out of the bearing and grease from the bearing out of the clutch. This is not a really big deal, and I bet either way is OK.
February 22, 2011
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
aarongillihan Comments: I'm a first timer as far as the clutch job is concerned, and this article made the job much less daunting. I do have one issue or question related to the flywheel and its pilot bearing. This tech article states to hammer it in "flush" with the surface, but my Haynes manual seems to indicate a gap should be left at the top, presumably for the felt washer. Is either method OK?
January 23, 2011
  Followup from the Pelican Staff: Yes, I think either way is fine. I've seen flywheels come out with no space - the felt washer is simply compressed there. - Wayne at Pelican Parts  

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