clutch release fork 1970 "S"

[tomster]

I wanted to replace the clutch on my 1970 "S" today and found that the release fork shows some decent wear. I just can't figure out where that wear would come from as everything was pretty much tightly tensioned.


The correct part number of the fork from the parts catalogue would be 911 116 712 01. The number on the part from my car says 911 116 712 1R though. Numbers are similar but different. Could it be I have the wrong part on my car or is the "R" just a replacement number for a superseded part?
Thanks for your help.
Regards,
Tom

[Frank Beck]

Decent wear compared to what? No unusual wear there.

If you're talking about the light scuff on the arm from the gold spring that's normal.
I get more chaffing on my legs from my underpants than that arm has on it.


But, do yourself a favor and replace the bolt while it's apart. They tend to break at the most inopportune time. And grease the pivot area and spring contact area before final assembly.

[Jon B]

If you're talking about the light scuff on the arm from the gold spring that's normal.

Frank, that scuff is not from the spring, but more likely from the arm hitting the cover of the clutch pressure plate.

Jon B,
Vista, CA

[tomster]

Thank you Frank. Wilco! Bolt is already ordered.
And for health's sake go change your underwear.

Frank, that scuff is not from the spring, but more likely from the arm hitting the cover of the clutch pressure plate.

That's what I kinda assumed as well, having read through some forums threads last night. As much as I found out the fork on my clutch (911 116 712 1R) is originally for a 901 transmission. I don't know though if it would also fit the pulled 911/01 schematic. But from above mentioned forum posts it seems quite a few people have the "1R fork" on their 911/01-gb. Most of them showed scuffings even way more severe than the ones on my fork. Could someone shed some light on this please?

I will go and measure the length of the guide tube next time I get the chance to pass by my workshop. There obviously is a difference in length: 901 (~40.5mm), 911/01 (50.0mm). I don't have the clutch right in front of me at the moment but could imagine that the PO('s mechanic) messed up some further parts on my clutch and used a 901-tube as he already put on a 901-fork instead of the correct one.

BTW, I read there must have been a change in forks between '70 and '71. First paragraph on the page below says that forks where "adjustable" at some point in time. I have never seen that kind of fork though yet:


What exactly is its purpose? Can you adjust the length of the pulling arm side?

[Frank Beck]

Frank, that scuff is not from the spring, but more likely from the arm hitting the cover of the clutch pressure plate.

Jon B,
Vista, CA

Now that I see the the fork more clearly I think you're right Jon. I've definitely seen worse.

Adjustable fork?
Would love to see that.

[tomster]

Adjustable fork?
Would love to see that.

At least that's what it says in the 1st paragraph:
"With introduction of the new adjustable release fork the clutch disc has to be replaced not until adjusting of the arm is no longer possible."

Anyway, any suggestions on continuing to use 911 116 712 1R on my 911/01 tranny?

I might not have fully understood the 911/01 pulling clutch but I would assume Porsche did not intend the pressure plate hitting the fork arm on purpose, right?

[Frank Beck]

I have a bucket of 2.2 forks at my other shop so can't survey part numbers ATM but can do it in the next couple of days. A conventional 901 fork or tube would never work on a push style 2.2 clutch so I'm not sure what you're referring to?

As for the scrapping mark... not uncommon and usually a result of someone cheating on the adjustment and overtightening the cable to compensate for a pressure plate that isn't fully releasing. (This also contributes to the pivot bolt breaking eventually.) Make sure your fork isn't bent; that can be a problem too.

[chris_seven]

I always thought that the 901 transmission was fitted with a 215mm 'push' clutch and used a fork with part number 901.116.711.11 (shown above) which was updated to 901.116.712.00.

In 1970 this was changed to a 225mm 'pull' clutch and the fork was changed to 911.116.712.01 along with the cable and other parts of the actuation system.

[tomster]

I have a bucket of 2.2 forks at my other shop so can't survey part numbers ATM but can do it in the next couple of days. A conventional 901 fork or tube would never work on a push style 2.2 clutch so I'm not sure what you're referring to?

Frank, if you could check on the part number from your original forks in the next days I'd gladly appreciate.

My above stated "shots in the dark" were exactly all that. I disassembled the clutch, found the marks, took some pictures and left my workshop to find wisdom.
It's the first time I disassembled a 911/01 clutch and I was trying to find plausible reasons (= shots in the dark) for the marks. That was all from my office desk trying to recall what I had seen in the workshop.
I think I have misunderstood Grady's posting over at the Pelican completely:
http://forums.pelicanparts.com/porsc...ml#post3245463
I thought that the "issue" he referred to concerning the differences in tube length could be the reason for the clutch not releasing properly. If you look closely at the picture with the tube comparison you might notice that the wear-marks on the tube to the left (901) have slightly less off-set from the top than the 911/01 one. And that lead me to the completely nonsense conclusion that there would be less clearance thus more wear on the arm. Obviously I stopped thinking from there (and most probably should have better stopped thinking way earlier...).
Apologies for that.

In 1970 this was changed to a 225mm 'pull' clutch and the fork was changed to 911.116.712.01 along with the cable and other parts of the actuation system.

Yep, but I was wondering why the number on my fork is 911.116.712.1R. I cannot find that number in the parts catalogue. Yours is well there (at a slightly frightening 615 €). Call me anal, but the German in me wouldn't let count 911.116.712.1R for a 911.116.712.01...

[chris_seven]

The 'R' designation is found an may different parts the most common being the '7R' mag cases.

The XXX.XXX.XXX. 1R isn't the Part Number but is most likely the number of the 'die' for a forging or the 'pattern' for a casting and I am not sure if a 'cross-over' list is available but one must exist somewhere.