clutch arm free-play on 901 trans cars (up to '69)

[RWebb]

I am wondering how much movement there usually is in the clutch arm on cars from 1965-69 (these cars had the type 901 transmission).

The play or jiggle that I am talking about is without the cable being connected (i.e. not free play at the pedal when you go to adjust the clutch). Instead, I am talking about the amount you can move the clutch arm by hand when you have the transmission mounted to the motor but not cable installed.

Does anybody know this?

I find I can only move the arm about 1 mm and then it stops - we think it might be hitting the pressure plate (the rounded cover). I have a custom setup that I am trying to get working - it uses several pieces from a 1969 style clutch.

[Grady Clay]

Randy,

Something is amiss there. I would expect about 1 cm or more of play. Where is it touching at the two extremes? Are the fingers of the pressure plate roughly parallel to the flywheel surface? Exactly what are the parts?

On my old 2.6 race engines (91x66) I used 906 flywheels, the ’69 only aluminum with flame-spray steel pressure plates and the thin ’69 only street (not 906) discs. I had to build custom spacers between the flywheel and pressure plate.

Best,
Grady

[Mo_Gearhead]

QUOTE:"...a custom setup that I am trying to get working - it uses several pieces from a 1969 style clutch."
__________________

Not sure if different year P-cars are like other makes but ...if you are mixing/matching components make sure you are using the correct T.O. bearing for your setup.

Do some have a slightly longer 'neck' (where the groove sets farther back)? Would not take much to close up that clearance.

Just food for thought.

[Beetle Bailey]

Like Grady asked" what parts are you using" I am very curious what setup that you have and what parts from the 69 are being used. I came from and old American hot rod school and took me forever to finally figure out how to adjust the clutch to work correctly. Needless to say I have had the engine and tranny out several times to "LOOK" for my problem. I'm not sure that I have an answer but I'm pretty familar with the '69 setup.
BTW sure appreciate your's and Grady's post.

[RWebb]

Thanks.

Grady - this is the same problem I've had for a looong, loong time. A person said he would fix things so I could use a 1971 (type 911) trans. on my 3.2L motor. I eventually got back a customized flywheel with a builtin ring gear (like on the 901 flywheels), but with a center section that would fit onto the 3.2L crank end.

The clutch is 901 type (Sachs Racing clutch), and the 901 clutch arm and throw-out bearing are used with the pivot point relocated. A 901 type ball pivot is used.

The original problem was that starter pinion gear would not engage with the ring gear -- the ring gear did not stick out enough. It did catch by about 1 mm tho. and worked for several months (most of which time the car the was in the paint & body shop). It failed and after months of trying to diagnose the problem (stated above) I discovered the mis-match. I sent it back to the guy and after about 7 months he finally sent me something back. It was not a new flywheel with the ring gear in the proper position. Instead, he had merely tack welded a spacer onto the back of the flywheel and drilled some hole for the (longer, 928 style) flywheel bolts to go thru.

I tried this setup, and it did not work. The starter worked, but the clutch did not work. I was unable to get the clutch to disengage properly. Also, as posted before, the ball pivot appears to have bent slightly.

Next, I have put some spacers under the ball pivot to try and move it out (i.e. it is moved in the same direction as the flywheel spacer moves the flywheel clutch grabbing surface, and the clutch assembly). That is the situation now. There appears to be only about 1 mm of jiggle or movement in the clutch arm with the trans. & motor mated but without using the clutch pedal to move the clutch arm (just my hand).

I am wondering how I can be sure it does not work; and how I can see if it will maybe work before putting the whole damn thing back in the car again - R&Ring the whole power unit in Oregon's freezing wet temperatures and my tiny narrow garage is getting pretty old.

Thanks!

[Grady Clay]

Randy,

I thought we had all those clutch issues resolved a couple of years ago. Let’s go solve this once and forever.

First is the general configuration; a Type 911 transmission (911/01) converted to the smaller 215 mm push-type clutch. You repositioned the clutch arm pivot for the earlier arm. We discussed the depth from where the pivot sits compared to the bell-housing mating surface. I just measured the copper sealing washer that goes under the pivot ball to be; 1.0 mm (10.85x8.05x1.0 mm). This is from a period transmission gasket kit. My recollection is OE was significantly thicker on the aluminum case transmissions. I’ll do some measurements on virgins.

Another important dimension is the ‘depth’ of the flywheel. That is the distance from the friction surface to the seating surface for the pressure plate. Spec for that is 22.5 ± 0.2 mm.

We discussed that there are two (at least) different clutch lever arm ratios at the pedal assembly.

I guess I didn’t realize that the flywheel wasn’t standard. Of course part of this may be my faulty recollection and be a mush of all my posts on this subject. I’m concerned about “…spacer moves the flywheel clutch grabbing surface ….” I don’t think it ever desirable to have a ‘spacer’ between the crankshaft and flywheel. Are the Sachs Racing clutch parts compatible?

I think we need to determine exactly what you have and compare the dimensions, etc. to standard parts. There is a lot of potential for mischief here.

For example, I would want to compare the distance from the engine-to-transmission mating surface to the flywheel friction surface. What you have to standard 2.0. You have a standard 3.2 engine?

Another would be to confirm the position of the clutch arm pivot ball. Is the clutch arm ‘straight’? They have been known to be bent or modified.

How did you support the end of the Bowden tube at the transmission side cover? Did you install a ‘reducer’ bushing in the ’70-’71 side cover or use a side cover from a ’69 mag 901/13 (I’m not sure that fits)?

It would be useful to post some images of the clutch arm at each extreme. What is of interest is the clearance in the bell-housing opening and what limits its travel.

If the clutch arm (or other) has been restricting the limit of travel and not the clutch pedal stop, there is risk of the clutch cable tube in the chassis (tunnel) coming loose. The first place to inspect is where the Bowden tube seats at the chassis bulkhead.

I have a suspicion that we will find the issue with the non-standard flywheel. Just a guess.

Happy New Year

Best,
Grady

[RWebb]

Thanks, Grady. We plan to make some measurements today.

"resolved a couple of years ago" -- I thought so too. I was happily driving the thing until the starter pinion got all ground away. The current problem is the result of this guy's cheap fix of sticking a spacer in between the flywheel and the crank. It is clear that he should have modified the ring gear or gotten whoever made up this flywheel (Kennedy or Patrick) to make a new one. But it is me who is left holding the bag, and him who is left holding the money.

The Sachs clutch parts look like the pics I've seen of regular 901 type clutch parts, and worked fine before he put the spacer in there. So AFAIK they are compatible.

My 3.2L motor has carbs and SSIs on it. There are no sensors near the flywheel to worry about. AFAIK, the crank and so forth is stock.

"Bowden tube"?? I thought only the '70-'71 had this?? The clutch pull wire does have a plastic cover over it part of the way. The guy simply welded a chunk of Mg on the case or side cover and milled it to hold the tube. I've posted a pic of this before but if you want to see it, I can post it again.

I hope your new year is going well.

[RWebb]

Here is a diagram of the 901 style flywheel (maybe from a Tech Spec. Book? factory manual?). It was posted on a related thread by John Cramer and Walt Fricke posted some additional dimensions.



To keep things straight:

proximal = closest to motor; towards rear of car
distal = furthest from motor

a = 22.5 mm = the distance from the surface the pressure plate bolts to, to the surface that the clutch disk grips. It is essentially the space that the clutch disc has to move around in.

6.5mm is the distance from the surface the pressure plate bolts to, to the (distal) face of the ring gear. [If the ring gear teeth are not far enough into the transmission (far enough away from the crank), then the starter pinion gear will not engage properly. This was the initial screw-up that the machinist caused.]

4mm is the depth of the lip that surrounds the surface that bears against the end of the crankshaft. That is, if you set a 901 flywheel on a flat table, with the pressure plate side up, the surface that bears on the crankshaft would be 4mm from the table. [On my setup, the machinist cut off that lip (we don't know how much "extra, if any, that he cut off].

In the table scenario, 52mm would be the distance from the table to the (distal) surface of the ring gear.

So, the distance from the crank to the distal surface of the ring gear teeth should be 48 mm (52 mm – the 4 mm lip).

{Thanks to Scott Clarke for figuring this all out.}

[RWebb]

The custom flywheel I have was made wrong to begin with, and the ring gear was too far away from the starter pinion (the ring gear was too proximal to the engine).

Instead of getting a new flywheel custom made correctly, the machinist just added a spacer underneath (at the crank mounting surface). This screwed up the rest of the geometry, causing my clutch to not disengage, no matter how far I pushed down on the pedal.

Shown below are 3 architectural drawings of the (simplified) flywheel set up. At the top is the stock 901 flywheel (based on the diagram above). In the middle, is the way my flywheel is now. And, at bottom is what my flywheel will look like if it is machined as we propose.



We think the thing to try is to have a (different) machinist
[1] cut 0.5 mm away on the "top step" to make it deeper. This would create the correct dimension a.
also
[2] cut 1.6 mm off of the spacer at the "bottom" of the flywheel. That will bring everything closer to the crank by 1.6 mm. In particular, the ring gears will move away from the starter pinion by 1.6 mm (but that should not be consequential as they are about 1 full cm wide); and the pressure plate will sit 2.1 mm (1.6 mm + 0.5 mm) closer to the crank. i.e. the "top step" will be 4.2 instead of the existing 6.5 mm - even tho it will not be the stock 6.5mm, it might be close enough to work

This may not be enough, but it is 10x cheaper than trying to buy a new custom made flywheel somewhere.

Ideas?

Thoughts?

[Scott Clarke]

Randy-
Removing the 1.6mm will position the ring gear in the stock location relative to the pinion. It is currently too close to the pinion.

[Grady Clay]

Randy,

Disregarding cost, I would suppository this flywheel with the prior (expletive deleted) and ‘do it right’.

First, I would use the 225 mm pull-type clutch. With care the ’70-’71 ‘Rube Goldberg’ clutch works just fine – certainly better that the previous hack job.

I think a standard 3.0 flywheel with an appropriate clutch, a 2.2 arm and linkage will work just fine. Nothing custom or strange.

I’ll be glad to help with the details.

Best,
Grady

[RWebb]

Even if I cannot afford it, I'd like to explore that option while I have your attention...

You would put a 3L (SC-type) flywheel on my 3.2L engine?
Then you'd put in a stock 1970-71 disc, pressure plate and ring gear?

Then what? Would I buy a new clutch cable? What about the curved Bowdoin tube for the '71 cars? And doesn't the trans require something welded onto it to accomodate that bent tube thing?

Scott has a stock '70 or '71 trans I could model off of, BUT...

keep in mind that there is absolutely no one within 100 miles of here that knows what to do to repair or modify a 911...

[Scott Clarke]

You have the stop for the clutch cable sawn off the gearbox, so that would be a problem. I don't rember if the loop for the boden cable is intact. If you did have the cable stop, it would conflict with the crossover oil line you have (at least this was the case with my car- several S Registry members report not having this problem. See recent oil line thread).