'70-71 T.O. arm play?

3liter914-6 · 05-17-2004, 04:07 PM

Hi folks,

I just put the 3.3L back in my 914-6. It was converted using the pull type clutch from the 2.2L cars on a 901 box. It took hours of screwing around with the arm and the T.O. bearing but I have the ears under the arms properly. However, I'm a little worried because it seems to be looser than I remember. Without the clutch cable hooked up, I can push the bearing out from under the arms fairly easily. Is this normal? I remember it feeling tighter, but nothings changed.

Is there much chance of it falling off? The Bearing doesn't rotate much under normal use, does it?

Thanks,

Adam

Zeke · 05-17-2004, 04:45 PM

It wasn't meant to be pushed the way you are doing. You might be fine. There are specs for where the arm should be at rest on the clutch diaphram fingers, or arms, if you have that type of pressure plate. If not in spec (and you should pretty well be able to tell if the thing is going to fall short when pushing down on the TO/PP), you might have to put a thick washer under the pivot. A resurfaced flywheel will almost certainly require the washer to make up for material (distance) lost in machining.

Grady Clay · 05-17-2004, 04:48 PM

Adam,

Do you have the finger spring (#4) in place?
Is it bent sufficient to maintain contact with the arm?
Is the TO bearing rotated 90 deg from the installation position?

I’m sure you know the TO guide tube is longer for the 2.2 than the 2.0.
The 2.2 pivot (#5) is not in the same location as the 2.0.
"

"
(C) 1970 Dr. ING. h.c. F. Porsche K.G.

Another trick you can do is to grind a grove in the face of the guide tube
where it contacts the transmission case.
The grove should go straight down from the input shaft seal.
This provides an alternate path for any oil that leaks past the seal to
not go directly into the center of the clutch.

Best,
Grady

3liter914-6 · 05-17-2004, 04:58 PM

Quote:

Originally posted by Zeke
It wasn't meant to be pushed the way you are doing.

It's not? The cable is just coming straight back from the firewall to the arm, and when I push the pedal it pulls on the fork.

Quote:

A resurfaced flywheel will almost certainly require the washer to make up for material (distance) lost in machining. [/B]

That's what it is. I forgot about the resurfacing. Looks like the tranny comes down for the second time today. DOH!

Thanks for the help.

Adam

3liter914-6 · 05-17-2004, 08:05 PM

hmm, ok that's 4 times I've had the tranny in and out today. Stuck a washer under the arm, where it screws into the tranny, put it back together and didn't notice an improvement, if anything it was looser. I put it back together without the washer, and I'm just not going to worry about it unless I have a problem in driving. I'd guess that the looseness would manifest itself by not engaging the clutch as much?

Thanks for the diagram Grady, you sure seem to have a nice stash of really neat stuff. I don't have the #4 piece, but this whole setup worked without any issues before I rebuilt the engine, so while it may be important, it's not causing the looseness that I'm experiencing.

Thanks,

Adam

Grady Clay · 05-18-2004, 07:22 AM

Adam,

I also think you should follow Zeke’s advice.

If the finger spring (#4) isn’t there, that moves the pivot (#5) about 0.5 mm away from the flywheel. If you machined the flywheel, say, 0.5 mm you would want to add an additional 0.5 mm washer for a total of 1.0 mm. As I recall the washer (#3) is a very substantial washer, not your common body washer and was thicker than a normal 8 mm flat-washer. The washer (#3) has part number 911.116.743.01 indicating it is a custom clutch only Porsche part.

I would get the Porsche washer (#3) and finger spring (#4) 911.116.774.01 and add about 0.7 mm washer under the pivot. The limiting factor is the fork (#2) can touch the pressure plate (undesirable) when the clutch is fully depressed. If it touches, it only hits the raised aluminum part of the pressure plate housing and won’t do any serious damage if only light contact. Without having the position of the pivot correct, the clutch won’t fully release under all circumstances. This can damage the syncros. Another limiting factor is when the clutch pedal is fully released it must not contact the transmission housing where the arm comes out of the bell-housing. This would keep contact with the TO bearing and could possibly prevent the clutch from fully engaging, allowing it to slip under load.

BTW, do you have the clutch cable Bowden tube anchored to the bell-housing? That tube needs to have a slight bow to it to accommodate the slight fore-aft movement of the engine/trans. Otherwise the clutch is very chattery –grabby and difficult to engage.

Don’t feel bad if it takes you several tries to get this right. Having a properly functioning 225 mm clutch with your big engine is an absolute necessity.

These part numbers are from 3/71 Part Manual update and may update to later numbers.

Best,
Grady

3liter914-6 · 05-18-2004, 08:50 AM

Hi Grady.

Thanks for your help. I've got a call in to Stoddard, and hopefully they'll be able to get me the parts.

I just want to make sure I get this right. If I put a washer under the base of the TO arm bolt.

It will move the bolt back towards the PP, but will move the contacts of the arm towards the transmission bellhousing placing more tension on the throwout bearing when it's rotated underneath the fork.

I don't really understand it I guess. Wouldn't the washers just move the whole assembly back giving me even less tension on the TO bearing ears when untensioned? Is this really what it does, but because I'm spacing it out, the cable end of the fork is limited in its pivoting by the transmission cutout and therefore the fingers on the fork can only go so far back towards the PP.

Wouldn't resurfacing the flywheel move the PP .5 mm away from the bellhousing and actually cause more tension on the ears of the TO bearing?

Thanks,

Adam

Grady Clay · 05-19-2004, 09:26 AM

Adam,

Yes, you are correct. The pivot bolt (#5) goes through the fork arm (#2) and seats on the washer (#3) and clamps the finger spring (#4) in place. Any additional spacer washer goes on top of the washer (#3) and under the pivot bolt (#5).

As I recall, there are detents under the ears on the TO bearing (#8) that help locate the fork arm (#2) in the correct position and prevents the TO bearing from rotating to the flats where the fork arm can come off. The finger spring (#4) purpose is to maintain contact between the fork arm (#2) and the TO bearing (#8) and the fingers of the clutch pressure plate.

In the “neutral” position, where there is no actuation of the clutch, the only force on the TO bearing should be from the finger spring (#4) except some very slight residual contact from the clutch cable. The clutch cable must have slight clearance when not actuated. Do not rely on the clutch cable to maintain contact between the fork arm (#2), the TO bearing (#8) and the clutch.

I assume you have the steel (not plastic) pivot piece where the clutch cable connects to the fork arm (#2).

From my last post:
“BTW, do you have the clutch cable Bowden tube anchored to the bell-housing? That tube needs to have a slight bow to it to accommodate the slight fore-aft movement of the engine/trans. Otherwise the clutch is very chattery –grabby and difficult to engage.”
Please show what you have done here. I think a 2-3” bow is about right. I put the Bowden tube adjusting nuts at the new (homemade) bracket with some of the threaded tube going through the bracket. I had both the clutch Bowden tube and clutch cable adjustable with double nuts. Just like the parking brake, these were custom modified OEM cable assemblies.

Best,
Grady

PS: IF you find CAS not under his 917, say HI for me.