915 Clutch total travel, free play, and adjustment

yelcab1 · 03-03-2022, 10:44 AM

I have a question on a 915 (84-86) gearbox clutch arm.

I had several of these cars and I have never been able to get the total 25mm clutch cable travel at the clutch arm. I have always had to zero out the free play otherwise it would grind going into gear.

Fast forward to today, on a 915 gearbox with a 964 engine in a 71 chassis, using a new clutch cable for the 915. I got a total of 18mm clutch travel, that is all. It would grind going into gear even if I take out the zero free play.

So I went negative free play, meaning adjusting the screw to push a little bit on the clutch arm (like someone is riding the clutch). This configuration lets me shift into all gears without any grinding. But, I think I am getting throw out bearing noise.

Any thoughts on what I should do next?

I am pretty sure the clutch big arm, little one, and the helper spring are installed correctly.

walt · walt's Garage

At the pedal cluster did you set the cable engagement to the clevis at the recommeded dimension? I'm assuming nothing itself is obstructing the actual pedal travel.

proporsche · proporsche's Garage

do you have the stop on your floor board??

Ivan

yelcab1 · 03-04-2022, 12:18 PM

No stop on the floor board, no floor board at all

proporsche · proporsche's Garage

ok why not? what do i miss? the stop is there so you do not go and over extend the work on your pressure plate...

Walt Fricke · 03-05-2022, 07:51 PM

I know just what yelcab is going through. Back in the 1980s, when my '77 was new to me, I could adjust the clutch release so it would be at about mid travel on the pedal, or a little lower. I didn't have to hit the stop if so adjusted.

Fast forward to the mid '90s. Car had morphed into an SC, and after a racing wreck had its front end, back to about the shift tower, cut off, and a whole new (well, junkyard but straight) front end welded on. Shop did a great job. But I've had trouble getting the clutch where I like it. I replaced the wood floor board (disintegrating) with an aftermarket aluminum one, and bought the factory pedal stop. Had to take it off in order to get disengagement. I can just get by by screwing the 8mm bolt in so I can just wiggle the lever up and down, so not pressing on the TOB. But I have to put the pedal firmly to the floor to get into gear (especially the synchroless reverse).

At one point I deduced this was due to a distorted diaphragm spring in the pressure plate. A new PP helped, but I still have no margin.

Which has me wondering if perhaps the car didn't get stitched together 100% right? A little shorter could mean a lot.

Or, perhaps, am I missing out not trying to adjust the front cable clevis to shorten things as much as can be done without the threaded end inside the clevis bumping into the cross arm lever? You'd think adjusting the Bourdon tube at the transmission attachment could, in effect, shorten the cable just as well as doing it up front, but maybe that isn't really so?

proporsche · proporsche's Garage

How about the wrong clutch cable-the length

Ivan

yelcab1 · 03-06-2022, 06:01 AM

Quote:

Originally Posted by proporsche

How about the wrong clutch cable-the length

Ivan

Very possible. This Frankenstein has a 71 chassis, supposedly rebuilt pedal box, 964 engine married to a 915 (Carrera) gearbox. I already had to cut 6mm off the shifter tube just to get 2/4 gears. While this is supposedly 915 cable, maybe it is still too long for the combo. There is no more adjustment either at the pedal box or the gearbox.

Years ago, my 84 clutch cable tube came away from its welding points inside the tunnel and it was not possible to shift but the clutch feel was way different from this episode.

Rodsrsr · Rodsrsr's Garage

I didn't realize the 915 had different length clutch cables. Anybody know which one is shortest?

I have a similar issue. My 76 is running a 3.2 with a 1983 915. New clutch, pressure plate, etc.. New cable and its working now, but I had to cut some of the threads off at the clevis which allowed me to thread it in completely, in effect shortening the cable.
It works perfectly, but I'm at the very end of the threads at the gearbox. Its like the cable is just a little bit too long.

proporsche · proporsche's Garage

yel cab...there is plenty of material by the clevis on the cable to try tap it more extra threads ..what do you think?
Ivan

pkabush · 03-06-2022, 09:41 AM

Quote:

Originally Posted by proporsche

yel cab...there is plenty of material by the clevis on the cable to try tap it more extra threads ..what do you think?
Ivan

This sounds long a good solution

Walt Fricke · 03-09-2022, 01:36 PM

Thread longer, and cut off some of the original threaded cable end at the clevis. If you don't cut off some, you can't shorten more than you can anyway, as the end will poke into the short lever arm.

There have been at least four external clutch release arms back under the bell housing, but the three which took cables with three threaded ends used cables of rather different lengths depending on the arm and system. From ~1977 until the G50, however, the clutch end wasn't a threaded rod - it had a swedged on sort of cast or forged loop end, to attach to the harp spring release lever system used on the car in question, and those only come in one length.