915 Clutch Cable Adjustment Challenges

[Duc Hunter]

So I'm having a challenge as to what to do so I thought I would ask here. I have and 915 transmission from 1978 and I'm trying to adjust the clutch. Right now my old clutch cable is adjusted so that it is as slack as absolutely possible, meaning it has as many threads sticking out towards the rear of the car as it can (all the open threads are towards the rear, there are none towards the front of the car). My transmission has an Omega spring on it, and I know that I need to adjust the bolt so that it has 1.2mm of clearance without the cable, and then put the cable on the arm and dial the cable tension so that the 1.2mm gap closes to 1mm.

My first challenge is that when I remove the clutch cable from the arm the Omega spring is completely free and flopping around. It looks like it's in absolutely the right position, but in order to set the bolt to 1.2 I have to put my hand on the back of the arm the Omega spring attaches to and push towards the front of the vehicle just slightly to make sure it's in the right spot. Is this normal, or should I not have to put my hand up on that arm to set the 1.2mm gap correctly on the bolt?

My second challenge, and what I think is more my issue, is that once that adjustment to 1.2mm is made I cannot get the cable back on the arm. Yes I have the clutch pedal pulled all the way towards the rear of the car with a wheel chock behind it just in case. Even if I use a long screwdriver to pry the arm forward I cannot slide the cable on the arm, as I cannot move the arm far enough towards the front of the vehicle to slip the cable on. If I open the gap up one they. Bolt WELL beyond the 1.2mm, I can get the cable on. With my old cable as slack as possible this seems very abnormal. I checked the cable routing, it’s correct. The cable is at least 10 years old and at least 15,000 miles on it. Based on my research it seems the only way for me to solve this problem is to remove my gas pedal to get access to the clutch pedal rod where it connects to the pedal cluster, and make an adjustment at that end of the cable. My car just had 15 months worth of metal work and restoration done, and we put in a rebuilt pedal cluster as part of that. In doing so we made sure the adjustments on the new pedal cluster matched where the old pedal cluster adjustments were.

Do you guys think this is the right approach? Does anybody have instructions on how to set the pedal cluster end of the cable up? If you are replacing a pedal cluster and a clutch cable all at once, do you first make an adjustment up at the pedal cluster a certain way, that then enables you to makes the proper adjustments as I've laid out above at the transmission?

And yes I have done some searching, and I read a couple of very good articles, including the one that FCP euro posted on how to do this with great pictures. Hopefully you guys can help me out.

In the interim what I did is back the bolt off significantly, hook the cable onto the arm, and then adjust the bolt so that there's a 1mm gap. Doing this seems to have the clutch feel pretty good. It engages in the middle of the travel nicely. My concern right now is A) the cable adjustment doesn't seem to be right per everything I've read, and B) when I put the car in neutral and let the clutch out there's a lot of noise spinning in the transmission that I don't remember. Yes I know they make noise normally in neutral and you step on the clutch and the noise goes away. I’m wondering if my throw out bearing is riding the clutch diaphragm because i can't do the adjustment “properly.”

[yelcab1]

Quote:

In the interim what I did is back the bolt off significantly, hook the cable onto the arm, and then adjust the bolt so that there's a 1mm gap. Doing this seems to have the clutch feel pretty good. It engages in the middle of the travel nicely. My concern right now is A) the cable adjustment doesn't seem to be right per everything I've read, and B) when I put the car in neutral and let the clutch out there's a lot of noise spinning in the transmission that I don't remember. Yes I know they make noise normally in neutral and you step on the clutch and the noise goes away. I’m wondering if my throw out bearing is riding the clutch diaphragm because i can't do the adjustment “properly.” "

47 years old car with a who-knows-who-made this clutch cable. I doubt you will be able to adjust the clutch the "official" way, with the by-the-book freeplay. You did it the way I would do it. Hook it all up, then adjust it until it feels good. Then drive it.

[David Inc.]

Originally Posted by Duc Hunter

My first challenge is that when I remove the clutch cable from the arm the Omega spring is completely free and flopping around. It looks like it's in absolutely the right position, but in order to set the bolt to 1.2 I have to put my hand on the back of the arm the Omega spring attaches to and push towards the front of the vehicle just slightly to make sure it's in the right spot. Is this normal, or should I not have to put my hand up on that arm to set the 1.2mm gap correctly on the bolt?

Not normal at all, something is absolutely ****ed. Pictures?

Edit: There should be a little stopper on the trans that prevents the helper arm from moving rearwards on the body. Maybe it broke off?

Google this part: 91511607002, that's the part that the spring sits in. There's a little angled plate you can see with two screws on it. You have that thing?

[Duc Hunter]

Originally Posted by David Inc.

Not normal at all, something is absolutely ****ed. Pictures?

Edit: There should be a little stopper on the trans that prevents the helper arm from moving rearwards on the body. Maybe it broke off?

Google this part: 91511607002, that's the part that the spring sits in. There's a little angled plate you can see with two screws on it. You have that thing?

Not sure what you are referring to by the stopper????

As for your part number.....I am not at my shop with the car at the moment, and it's on it wheels. This is a pic from a month ago. Looks like I have that part. From the pic I cannot tell if it has that flat little L-plate that screws to it or not.

You can also see the bolt set up. In this pic it was not adjusted "right," though the clutch felt pretty good. It had been engaging at the VERY top of the travel, the cable was adjusted totally the other directions (no threads left like the cable was stretched bad), and the bolts gap was huge. I adjusted it to the point in the pic, and as I said above it felt pretty good. My "only" issues as of this picture was I was hearing a lot of noise in neutral, and decided to try to get it adjusted "more better" to see if that noise got better.

[David Inc.]

Originally Posted by Duc Hunter

Not sure what you are referring to by the stopper????

As for your part number.....I am not at my shop with the car at the moment, and it's on it wheels. This is a pic from a month ago. Looks like I have that part. From the pic I cannot tell if it has that flat little L-plate that screws to it or not.

You can also see the bolt set up. In this pic it was not adjusted "right," though the clutch felt pretty good. It had been engaging at the VERY top of the travel, the cable was adjusted totally the other directions (no threads left like the cable was stretched bad), and the bolts gap was huge. I adjusted it to the point in the pic, and as I said above it felt pretty good. My "only" issues as of this picture was I was hearing a lot of noise in neutral, and decided to try to get it adjusted "more better" to see if that noise got better.

The little angle bracket that screws to the larger bracket is the "stopper". The omega spring pivot shaft uses that as its rest position. That's why the omega is flopping around, and I think without that you'll never be able to get the cable adjusted properly.

Is the pedal depressed some in that photo? The pivot shaft of the omega spring looks forwards of the bearing bracket (the pin on the trans that holds the spring), and it should be rearward at rest.

There's also a ton of adjustment left on that cable there. It looks like you have it almost as tight as it can go.

Edit: Did that bearing bracket originally come without the little plate screwed in? I see that the part number is -02, not -00, so a revision.

Edit Jr: And if that's a pic taken at rest then yes, the fork is probably pulling against the T/O bearing and making some noise.

Edit III: Compare your photo to the photo in this post, which shows how the whole setup should be oriented at rest: https://forums.pelicanparts.com/porsche-911-technical-forum/1076300-omega-spring-install.html#post11073426

[gled49]

Look at pictures, u need the basic parts here.

[Duc Hunter]

Originally Posted by gled49

Look at pictures, u need the basic parts here.

gled49, thank you for the assist. Maybe I am confused. Aren't the parts I have in red below the ones you're referring to?

[David Inc.]

The part that the spring is on is missing the little angle bracket screwed into it. You can probably eyeball the helper arm into about the right position and then adjust the cable and bolt to 1mm, but like you're experiencing it isn't going to be right.

[Duc Hunter]

Originally Posted by David Inc.

The part that the spring is on is missing the little angle bracket screwed into it. You can probably eyeball the helper arm into about the right position and then adjust the cable and bolt to 1mm, but like you're experiencing it isn't going to be right.

Ah ok. In my picture I think I can see the bolts that hold the plate on. From the picture it looks like maybe they are just broken off in the aluminum bracket and the plate is not there. I will check when I get to my shop, and if so, get a new one. Thank you!

[pmax]

It should look like the last picture in this post.

915 Clutch Helper "Omega" Spring Function

[Duc Hunter]

Pmax, I turned your pic around to match my pictures orientation.



It looks like in mine the Omega spring is not attached, which may have been the case when I snapped this picture but is absolutely not the case as the car sits now. My challenge/question is that without the cable on arm my spring can be pulled off (blue arrow shows how it would move off, green is is off the pin) the inboard pin that holds the spring with my hand. Nothing is retaining it in the position on the pin in your picture but the cable’s tension. As a result when I go to adjust everything, starting with the cable off, I have to;

1. get the spring in the right place
2. push that part of the arm forward to keep the spring in place
3. holding all of that there with one hand then I adjust the bolt to 1.2mm (need 3 hands)
4. Then re-attache the cable. This is impossible as even with a lever off the transmission (long screwdriver) I cannot move the fork far enough forward to get the cable over its hook and onto the arm. Now I am laying on the floor, reaching in from the passenger side wheel well with the wheel off the car, so leverage isn’t as god as when it was up on a lift and I tried this before. This is the step that makes me think the pedal adjustment is way off, as I should be able to get the cable slack enough to push the arm forward and get the cable on the arm, right?
5. As a result of that step not working for me, right now I simply put the cable and spring in their place with the bolt backed way off (gives me the “slack” to get the cable on by hand), then I adjusted the bolt gap the be 1mm. As you can see my cable tension is backed off as car as it’s housing will permit.

Maybe I am not explaining that right? Or maybe I am missing something.

I will still double check that the plate mentioned above is attached to the mount. I am not sure how that plate would help my issue though.

[proporsche]

this is L shape bracket - i have them made and sell them for $10
Also it does not look you have pulled the clutch cable all the way back towards the engine .This is done before you install the little finger with spring

[pmax]

In your step 4, it appears your cable is too short. If so, lengthen it at the pedal.

From the excellent FCP euro guide

Am I missing something ?

If that doesn't work, you can try without "springing" that omega. This later contraption seems like it's way overdesigned to me. If this is on the 75 in your sig, the pedal setup, and the original clutch lever mechanism without the fancy omega spring, differ from the SC which is the other possibility.

[Duc Hunter]

Originally Posted by proporsche

this is L shape bracket - i have them made and sell them for $10
Also it does not look you have pulled the clutch cable all the way back towards the engine .This is done before you install the little finger with spring

Let me double check mine (hopefully tomorrow). If I need them I will take 2.

Originally Posted by pmax

In your step 4, it appears your cable is too short. If so, lengthen it at the pedal.

From the excellent FCP euro guide

Am I missing something ?

If that doesn't work, you can try without "springing" that omega. This later contraption seems like it's way overdesigned to me. If this is on the 75 in your sig, the pedal setup, and the original clutch lever mechanism without the fancy omega spring, differ from the SC which is the other possibility.

Pmax, I will head up to the pedal and adjust that to maximize the cable length (within the 2 marks). That should help. My transmissions is a 1978 from an SC, and was rebuilt 15k miles ago by the PO.

Everyone….Thank you for all the advice!

[David Inc.]

If the cable worked before the rebuild then I wouldn't worry about the clevis, it's probably adjusted properly.

Again, according to your photo you have that cable nearly as tight as you can get it. You need to adjust it in the other direction.

You're missing a part and the adjustment at the clutch end is wrong, don't overcomplicate the situation.

[Duc Hunter]

I know this from bicycles. Laying under the car I have it backwards! There cable is max tight, not max lose! ARGH! Will report back after I fix my error.

[Duc Hunter]

So above I was right, So no "DOH" moment!

The more threads towards to back of the car, the more slack the cable is..... and the more threads towards the front of the car (relative to the bracket that holds the cabled adjustment section the the transmission) the tighter the cable will be. So all of my pictures it's as slack as I can get it, and as I mentioned above I cannot get the cable on the arm. So I will have to get up to the pedal box and make sure the adjustment there is right.

Cable adjusted to max slack


This is what happens to my omega spring. Without the cable on it, the spring can just come off its pin and swing towards the rear of the car. Also in this picture I can see I do not have the above mentioned little L Plate. This bracket only seems to have 1 screw hole as well, not he two noted above that hold the L Plate to the bracket.


To adjust the bolt's gap to 1.2mm I have to place my finger like this and push towards the front of the car slightly to keep the omega spring in place. I described this in a post above and thought a picture would help. I also noticed the gap from the mounting plate to the omega spring. Maybe its the pictures ProPorsche posted above and the perspective, but I don't see how that little tab on the bracket is long enough to help the spring stay in place, or have any impact on the spring or the arm. Hmm.


My next steps.....

1. With the cable off, adjust the pedal box clevis to 17mm, which should give me the most cable slack possible.
2. Come to the transmission and set the bolt gap to 1.2 mm, using my finger to hold the omega spring in place like the picture.
3. See if I can get the cable onto the arm, and if so adjust the bolt gap to 1mm.

[David Inc.]

That spring isn't even close to being in the right position. That little bracket keeps the spring in a bit of pre-load, you're not getting it in position just holding it with your finger.

The centerline for your spring is in red, its target rest position is in green, which is where the bracket would keep it. Once it's there that's where you would set the 1.2mm gap.



Also, the bracket that has only one hole, is the other hole maybe filled in with a broken screw? Almost looks like something is there, but can't tell from the pic.

Long story short you're not getting the setup right without that missing part. If you can't get the little bracket on, the larger assembly is available for not too much money.

Edit: The bracket will be enough to retain the spring, it doesn't need a lot of overlap.

[Duc Hunter]

Houston we have a problem. Looks like this is why I could never get enough slack in back. And of course as I tried to get the Clovis loose to adjust things,….all those threads sticking out just snapped off, with almost no pressure. I am pretty sure they were bent up because, with that much thread sticking out, moving the clutch pedal woud for the arm to bend the threads. UGH!!!

Good thing I have a new cable that I can slide in tomorrow, and set. This all up right.

[sigchuck]

Glad to see the start of a happy conclusion - I had a lot of operator induced frustration installing mine last year. I ended up rebuilding my pedal cluster as the hole in the clutch arm was a little out of round and the bronze bushing was worn through. Now is the best time to take a look - the clutch cable was definitely the hard part of the job. Joe engineer’s FCP blog has a great write-up on the pedal cluster rebuild also.