Clutch adjustment - what does this picture tell me?

HenrikL · 02:24 AM

Looking at the picture below, there is an large nut placed between the double nuts and the release arm. The larger nut has its threads drilled out and I guess it was placed there because there were not threads enough on the cable end for adjustment.

What does this tell me? Is the clutch cable bad or is the friction disc really worn? The gearbox is coming out for a rebuild and I have the opportunity to fix clutch issues at the same time.

morrisjm1 · 01-02-2008, 05:30 AM

Just a guess, but it is possible that the PO put the clevis at the petal cluster at the end of the cable making the cable too long. Instead of of crawling back under the dash (it is a PIA), he/she may have used that nut to effectively shorten the cable.

If you're having the tranny rebuilt, you definitely should replace the clutch disk, pressure plate, throw-out bearing, pilot bearing, cable, check the bushings for the actuating shaft, and have the flywheel resurfaced.

Good luck,
Mike

john walker's workshop · 01-02-2008, 05:45 AM

probably to compensate for the collapsed (shortened) bowden tube part of the cable assembly. from the looks of that cable assembly, it's old as dirt, and your clutch would feel greatly improved with a new one that allows the inner cable to slide on a fresh sleeve.

HenrikL · 01-02-2008, 10:47 AM

Thanks for the answers. The bowden tube was stuck in the transmission casing and today I just cut the cable with an angle grinder. New clutch cable must be added to the list of new pats.

Grady Clay · 01-02-2008, 11:26 AM

Henrik,
Welcome to the Forum

You will find a lot of help here.

I agree that you have the opportunity to make all these important parts new again and have everything working properly. There is a lot to that. The devil is in the details. Searching the Pelican site about 915 clutch details will reveal a LOT.

I would normally expect a ’77 to have the over-center ‘omega spring’ at the clutch arm. This may be a RoW thing or a PO modification. Your configuration is very simple.

I agree with John & others about the purpose of the nut/spacer. An issue there is can the nut contact the arm? The piece between the nut and the arm has to pivot freely as the clutch is actuated. If that nut contacts the arm, it limits the angular movement of the pivot piece and puts parts (notably the cable) in bending.

If a spacer is necessary after you replace everything, I recommend something that can’t contact the arm.

Other issues are the fork that engages the clutch release (TO) bearing and the bushings that support the shaft. It is wise to replace the bushings and seals and carefully inspect the fork for wear, cracks or bending.

Obviously you are replacing the clutch cable and Bowden tube. I’ll encourage attention to the pedal assembly also. The attachment of the clutch pedal to the cross-shaft can be an issue. So can the cross-shaft and plastic bushings (I like retaining plastic) and the lever and clevis attachment to the cable.

Based on your image, I would choose to replace everything possible related to the clutch and your reinstall. I would pay particular attention to lubrication and corrosion prevention.

Best,
Grady

Walt Fricke · 01-03-2008, 01:35 PM

My gray market Euro '77 came to me with this kind of release lever. No harp spring. It was a fairly early '77 (July or so of '76). I think '77 was a kind of transition year for some of the things that became standard on the SCs.

Walt Fricke

javadog · 01-03-2008, 03:58 PM

I also noticed the lack of an Omega spring. I'd suggest taking a look at the transmission type number and serial number to make sure what you have. It's possible that you have an earlier gearbox. Many things changed between 1976 and 1977 and you'll obviously need to know what you have before you order your parts.

For what its worth, I also have a 1977 ROW 911 and it has the later style clutch release arm. It was produced after the August '76 factory holiday, which is when I have always assumed the changes took place.

JR

HenrikL · 01-06-2008, 01:48 PM

The car has chassis number 91173013xx and the gearbox is of type 915/60.

javadog · 01-06-2008, 05:35 PM

Henrik,

That's really interesting. You have the correct gearbox type for your car, and for your car's model year. The car's chassis number indicates it wasn't an early car, but that it was built midway through the production for that model year. Do you have anything that tells when the car was first delivered to a customer, or when it was built?

I have to admit I'm a bit mystified as to why the clutch release mechanism lacks the later design with the spring.

JR

Walt Fricke · 01-07-2008, 06:53 PM

While teasing our brains about just what parts a given 911 ought to have is fun, I'd not lose any sleep over this. The clutch release mechanism you have is just fine. And, because simpler than the harp spring system, even can be seen as an advantage.

My track car has a Carrera RSR pressure plate. You'd suppose its diaphragm spring is as stiff as they came (though I think it is not any stiffer- it is not thicker than ordinary ones). I often wondered why that clutch took so much less pedal pressure than the harp springed one on my daily driver SC. Replacing a broken harp spring brought some relief, but not forever. Then I replaced the clutch cable, and voila - much much less effort. So you should be just fine with what you have (when it is all back in working order).

Walt Fricke (left leg getting progressively weaker due to less exercise)

javadog · 04:25 AM

I know it seems like sometimes we get lost in the small details for no reason but, if you get back to my earlier posts, Henrik is going to have to be careful when ordering parts. He'll need the earlier clutch cable which isn't what the parts guy would ordinarily order for that car. Maybe the reason he has the extra nut on his cable now is because the cable has been replaced once and the wrong cable used.
As for the clutch, would a '76 or '77 disc be the one to get?

JR

HenrikL · 01-09-2008, 12:51 PM

Quote:

Originally Posted by javadog

Do you have anything that tells when the car was first delivered to a customer, or when it was built?

No, I do not know much about the car's early history. It was sold new in Germany and imported to Sweden in 1988.

safe · safe's Garage

Hi Henrik!
My ROW 77 has the same arm too. It was registered the 16th of march 1977, not sure when it was manufactured, I guess its pretty early 398 out of 1724.

Walt Fricke · 01-09-2008, 11:15 PM

JR

The 915 clutch disks are all the same.

You sure are right about needing to be careful in ordering a replacement cable. The harp spring cable is easy to spot (and, for Henrik, to avoid) as it has a biggish forged loop end swedged onto it. No use unless you have that kind.

There are a couple of other kinds with straight threaded ends.

One will be too long - too long I think even to work with a nut as a spacer added. That was made for a different type of single end lever arm which accepted the cable in a groove, bent it 90 degrees, and then had the threaded end go through a hole in a boss on the arm, where the adjusting nut held it. This developed a reputation as the design that broke cables (where they made that bend).

Two, I think, might both work. One is like what he appears to have had - a 6mm threaded piece on each end, allowing it to be pulled out of the Bowden tube and separately replaced. Another had an 8mm threaded end which was too big to be pulled through. Something like that. I only know of it because I once offered one of the 6mm kind to a friend who had broken the cable on his '74 at the track, but he couldn't use it. That kind, I think, comes with a new Bowden tube so both are replaced as a unit.

I think if he gets the kind that goes with the straight lever he should be fine. Our host's order takers often know many of these details. The first time I replaced mine, about 1986, the parts guy from the dealership came out to look under the car before he sold me one. Said he was glad he did, as he had the wrong one in mind before looking.

Walt Fricke

javadog · 01-22-2008, 07:46 AM

Quote:

Originally Posted by javadog

Henrik,

That's really interesting. You have the correct gearbox type for your car, and for your car's model year. The car's chassis number indicates it wasn't an early car, but that it was built midway through the production for that model year. Do you have anything that tells when the car was first delivered to a customer, or when it was built?

I have to admit I'm a bit mystified as to why the clutch release mechanism lacks the later design with the spring.

JR

I did a little research and found that Porsche offered a couple versions of the 915 transmission during the 1977 model year. Type 915.60 did not have the clutch assist spring and type 915.61 did have it. A 911 for the US market or a Carrera 3.0 would have had the 915.61 and the ROW 911 would have had the 915.60.

You learn something new (and often almost useless) every day.

JR