clutch cable for 70-71 901

[ckissick]

Can someone please explain the clutch cable installation for the 70-71 tranny? I have the explanation about the pedal play and clevis, etc., but I'm curious about how the fork moves. I have had the engine out for 6 months and forgot how it was now that I'm hooking everything up now.

My main point of confusion is the cable end in the back, and where it goes. As I remember, it slips into a small holder and then into an immobile tab sticking from the bottom of the tranny housing. I then adjust the two nuts on the cable so it bends up and the pedal play is correct. However, the cable end is fixed and can't move. So how can the fork move? Thanks.

Charlie
Montara, CA
1970 911E
1950 VW

[john70t]

I think that in a standard cable the guide is immobilized and the cable is pulled through it.
My guess is that on the push-type, the cable is immobilized as a rod/guide and the outer sheath is pushed/slid against the fork pivot(?). The freeplay is about 1 1/2" pulling the peddle up.

If yours still has the OEM plastic end(not likely), change it to the aluminum.

[Early_S_Man]

Charlie,

The '70 - '71 '911' version of the 901 transaxle was quite unique in that there was a 'U-shaped' trough or guide for the Bowden tube [clutch cable outer sheath] in which the entire cable was free to move up and down in [rather than being tied/clamped in place] ... and the actual movement of the end of the sheath with respect to the fixed cable end is what operated the throwout bearing actuating lever!

[ckissick]

John, I do have the aluminum part. Thanks, guys. What a strange design. I guess I'm on the right track, it just doesn't seem workable. I didn't know Rube Goldberg worked for Porsche.

Charlie

[Grady Clay]

Charlie,

Check this out then ask more.

'70-71 T.O. arm play?

I can post some illustrations if you need

Best,
Grady

[Grady Clay]

Charlie,

OK, back to 2.2 clutches.

Here is an overview of the cable and attachments.
“

"
(C) 1970 Dr. Ing. h.c. F. Porsche A. G.

The rear end of the cable is fixed to the transmission casting.
When you push the clutch pedal it tensions the cable and tries to straighten out
the Bowden tube. This pushes the clitch lever.


To get appropriate free-play you adjust the nuts on the cable.
"

"
(C) 1070 Dr. Ing. h.c. F. Porsche A. G.

If everything is correct with your pedal assembly and at the clutch arm in the transmission,
you should set to slightly less than 1" freeplay, pulling the pedal up.

A critical issue is that the clutch arm must not contact the transmission
housing in either direction.


If the Bowden tube sits low in the saddle (guide bracket):
"

"
(C) 1970 Dr. Ing. h.c. F. Porsche A. G.

then you must screw the front clutch clevis more onto the clutch cable.
Then readjust the free-play.


If the clutch cable bowden tube is about to pop out of the guide bracket:
"

"
(C) 1970 Dr. Ing. h.c. F. Porsche A. G.

then you must un-screw the clevis at the front of the cable.
Again re-adjust the free play.


This whole proceedure is a pain and time consuming.
It works best with all new parts (particularly the cable assembly)
and everything else working properly.

The condition of the guide loop in the side of the differential cover is very importsnt also.

You should be aware of any prior modifications at the clutch or pedal assembly.


Best,
Grady

PS: This would have made Rube proud.

[Randy Webb]

If you really hate the setup, here is a way to modify the clutch actuation

[awis321]

Off topic... Grady, where did you get those diagrams from? They're the best I've seen yet.

- Dennis

[Grady Clay]

Dennis,

Those are from a very early Factory workshop manual. It is so early it was just one binder. When binder 2 came out as a supplement they sent me a “1” decal for the original binder.


Randy,

Good point. Yes you can convert back to the push-type clutch (where the cable pulls on the clutch arm) but you are going to a smaller clutch (215 mm in place of 225 mm.)

I have seen some even more Rube Goldberg “fixes.” I remember seeing a 914 pulley affixed to an engine and a spliced cable.

With good parts the system works OK.

3liter914-6 is working to convert his 914-6 (901) transmission to the ’70-’71 225 mm clutch. This works well because the cable is in the “pull” mode in a mid-engine application. See the link above.

There are also some really cool lightweight 225 mm pressure plates with the housing made of aluminum and the moving part has iron plating on an aluminum forging.

Best,
Grady

[304065]

Those look like the factory workshop manuals.

[ckissick]

Randy, what happened to the poor thingy that the CV joint attaches to?

Charlie

[Grady Clay]

Guys,

Here are the cable parts.
"

"
(C) 1971 Dr. Ing. h.c. F. Porsche A. G.

The plastic piece (#83) is availble from our host in aluminum.

I think the lever (#32) in the pedal assembly has a different ratio from other years.

Best,
Grady

[porcupine911]

Apparently there is a lot of misunderstanding of this type of cable configuration... I found the cable completely outside of the guide on my car (PO was ignorant mechanically). The nylon actuation piece (#83) failed on mine a couple of months ago too.

Originally posted by awis321
Off topic... Grady, where did you get those diagrams from? They're the best I've seen yet.

Those same pics are poorly reproduced in the el cheapo haynes manual.

[Randy Webb]

Grady - good point -- I use a racing clutch - and the machinst/race engine builder swore I'd be OK.

Charlie - I drilled the flanges for light wt.! No, just joking - some guy tried to adapt the 911 trans. for use in a VW bus - I got it when that didn't work out for him.

Now: the crucial OT question in all this -- when putting a 911 trans. into a 1973.5 car, do I use the rubber boot that goes on the trans. shift rod for the 1973-on cars or backdate to the 1965-71 rubber boot?

[Randy Webb]

Grady -- Who sells the really cool lightweight 225 mm pressure plates with the housing made of aluminum and the moving part has iron plating on an aluminum forging?

And how much wt. do they save? I'm bound to wear out this clutch sooner or later.... (forgot to mention - the 911 takes a 225mm and the 1965-69 901 trans takes a 215mm, I have the former trans but with the smaller clutch (don't ask me why)).

[Grady Clay]

There is a modification to the 2.0 TO bearing tube here:
Transmission input shaft oil seal on a 69 what's involved in replacing?
That is equally applicable to the 2.2.

Here is a pretty good 2.2 clutch thread:
1971 T clutch cable....HELP PLEASE


As an aside, the 2.2 TO guide tube is longer than the 2.0 guide tube.


If you have occasion to get into the clutch area,
here is something to look for:
“

"
(C) 1969 Dr. Ing. h.c. F. Porsche A. G.

In the above illustration the early pivot parts (#5, #6, #7, and #11 ).
If you have those parts, replace them with the pivot (#5) in the lower illustration.
"

"
(C) 1971 Dr. Ing. h.c. F. Porsche A. G.

The early pivot part was very prone to breaking.


Another issue I should have mentioned is the arm (#2) can touch the perimeter
of the pressure plate under some conditions.
I have successfully ground away about 25% of the arm for clearance to the pressure plate.
I wouldn’t encourage taking anything off the pressure plate.
Although I have seen them ground off by contact with the arm.

At every opportunity inspect the ball socket in the arm
and the pivot for damage and keep them lubed.

Best,
Grady

[Grady Clay]

Randy,

It’s been too long. Try our host first. Try all the different suppliers then start looking for NOS. Stoddard is a possibility.

How much weight does it save? I was comparing to an all-iron pressure plate.

Let me understand your conversion. You have a ’73.5 chassis and a 911 (901) ’70-’71 transmission with a 215 mm clutch and flywheel.
I assume it was converted to the “pull on the cable” set-up. If that has been done on a ’70-’71 transmission case, did they (you) reposition the pivot?

Best,
Grady

[Randy Webb]

"did they (you) reposition the pivot?"

- Uh, what pivot? The little ball pivot for the fork? I dunno but I don't think he did.

(yes, that's what I have: a 1973.5 car; 911/01 trans; and a 3.2L engine with a conversion flywheel on it for a 215mm clutch).

[Grady Clay]

Randy,

In ’70-‘71 Porsche used the same transmission casting (Type 911/xx, magnesium) for both 911 and 914-6. The 911 has the 225 mm pull type clutch and the 914-6 has the 215 mm push type clutch. When you remove the clutch release arm you will notice the transmission housing casting has a semi-oval boss cast in place to support the clutch release arm pivot.
The pivot for the 914-6 215 mm push type is drilled closer to the input shaft and the 911 225 mm pull type is farther to the outside by about 15 mm. This causes a difference in ratio.

There is enough space and material to have inserts in both locations.

The 914-4s has a similar casting but of slightly different alloy and not as good molds as the 911/914-6.

There is also a subtle difference in the castings for ’70-’71 911s. Porsche reinforced the 911 casting slightly, I think starting in ’71. The obvious difference is the later casting has a cast boss alongside the ribs on the bottom of the differential for the type number and serial number. The earlier version had the numbers stamped in the bottom rib. There were some other subtle changes also.

In ’69 Porsche experimented with several different clutch arm ratios. I think I found three different ratios for the 215 mm push type clutch.

Can someone chime in here? Do I remember ’69 models with the magnesium case?

Best,
Grady

[Oldporsche]

I believe that my '70E has an alum case, Grady. The hole in the case where the sheath rides gets worn out. I bushed mine with a brass busing that I turned in my lathe. It's grooved on one end to hold a "C" ring type keeper.

I'll have to crawl under it for another look.

Good luck,
David Duffield

DiMarco's 914-6 case however was different than mine. I believe that his was a '69.