915 clutch adjustment woes

cowtown · 07-27-2004, 07:04 AM

Good morning, I need some help with 915 clutch adjustment.

I just put a rebuilt (synchros, dogs, sliders, seals) 1982 915 into my early 1975 911S. This car previously had the old-style 915/40 with no helper spring.

Along with the new transmission, I installed a new hooked cable to go with the helper spring layout.

I have adjusted the clutch per the shop manuals, with 1.0mm between the locknut and arm. However, no matter what I do I can only get 19mm of cable travel (spec is 25 +- 0.1mm). I have the floorboard installed, but have completely removed the pedal stop and carpet. The pedal travels through the entire range allowed by the floorboard.

What am I doing wrong? The car shifts fine, except it's difficult to get into first gear from a dead stop. Is this symptom consistent with lack of cable travel?

Thanks!
Colin

PS I've adjusted the shift linkage (which also has new bushings) several times and it always feels about the same. Only first gear is giving a problem.

SC-targa · 07-27-2004, 10:54 AM

Sounds like your clutch is dragging. What happens when you shift into reverse? It's not sychronized, so it will grind if the clutch is dragging. Did Porsche change the leverage ratio on the pedal cluster sometime?

Jerry Kroeger

cowtown · 07-27-2004, 11:51 AM

Quote:

Originally posted by SC-targa
Did Porsche change the leverage ratio on the pedal cluster sometime?

That's a very good question.... Maybe I need a different actuator on the pedal cluster?

Reverse is fine. Slides right in, no grinding (as long as I wait a couple seconds with the clutch in - my old 915 required that brief wait too).

Do brand-new synchros need to be "broken in"? It's only 1st gear that's the problem, though.

Doug Steinel · Doug Steinel's Garage

What does the term "dragging" mean when applied to a clutch?

SC-targa · 07-28-2004, 06:40 AM

Just that the clutch is not fully disengaging.

Jerry

Hladun · 07-28-2004, 07:15 AM

Did you set it as required; 1.2mm cable loose/off (adjust bolt) and then 1.0mm cable on (adjust cable on transmission case)? You may have slack in the cable.

cowtown · 07-28-2004, 07:52 AM

Yes, I set the bolt/arm gap to 1.2, then used the adjuster nuts on the cable to go down to a 1.0mm gap.

I didn't have time to work on it last night, but I think I will try to move the clutch engagement position up closer to the top of the pedal. Maybe that will give me more throwout bearing travel.

I still don't understand why overall cable travel is limited to 19mm, though. Something is not right with my linkage or pedal cluster.

Hladun · 07-28-2004, 11:57 AM

I'd check the pedal assembly. Is the clutch pedal returning all the way? Is anything bent? Is there any play in the roll pin? The greatest movement is acheived when the cable arm on the pedal assembly starts at 45 degrees reward and swings to 45 degrees frontward (1.4 times the arm length). Is your arm doing this?

Carl Bauer · Carl Bauer's Garage

I had a somewhat similar problem where I could not get the clutch cable to pull far enough towards the front of the car. I eventually found that the roll pin in the cluster was falling apart. The clutch pedal was rotating w/o the cable moving enough.

Eagledriver · 07-28-2004, 01:50 PM

If the bushings in the pedal cluster have failed you will get less travel because the base of the pedal will move forward slightly instead of just rotating. If you have enough movement to keep the clutch from dragging (reverse gear test) then you have enough travel. Be careful about going for too much throughout bearing travel-you could damage the clutch pressure plate.

-Andy