Out with a bang?

[mjohnson]

What sounds can a breaking clutch cable make?

I was heading off to a meeting this morning in my '78 SC.

I pulled out of the parking lot and heard a pop/bang/thunk shifting from first to second. The sound was loud enough to alarm my passenger, but not super loud. The engine revved freely and we coasted to a stop with the shift lever back in neutral. There were no additional 'strange' sounds.

I shut it down immediately and checked underneath. There was nothing unusual to be seen, though maybe I could see more of the ground strap near the starter side of the transmission. No fluids, nothing large left on the ground where the bang happened.

With the engine off and the door open, _maybe_ I could hear something different while stepping on the clutch pedal.

I was on a gentle slope and I let it roll backwards, engine off and gearbox in neutral, a few feet. No binding or crunchy sounds. I rolled it back another hundred feet into the parking lot and parked it. We took her car to the meeting.

So I sit through the boring meeting thinking about the car...

Actually, I was reliving the horror of paying for the 915 rebuild I had done last spring. That time, there were lots of sounds from below with some unnatural lurching. This time, silence. Hopefully that means it's not the gearbox.

I hypothesize that a broken clutch cable, if broken with the transmission in neutral, would keep me in neutral with the engine running but allow me to shift into gear with the engine off.

After the meeting, I head out to the car. With the engine off and in neutral the car rolls freely a few feet in each direction. Shift it into first gear and it barely rolls forward, none at all backwards. Shift it in reverse and it doesn't roll forward, barely rolls backwards.

Does this sound like a car with a broken clutch cable?

If so, what are the chances of starting the thing in gear and driving it home (4 miles) without using the clutch? I've arranged a drag out to the highway where it can sit until late tonight or wait for a flatbed. I'm a mile or so into my employer's property and they would frown on me doing repairs in the parking lot or leaving the thing for the night. Letting a tow truck in to get the car isn't going to happen either.

Arrgh?!

Was this a $100 bang or was it a $2500 bang?

mike in Los Alamos
'78SC

[svandamme]

broken clutch cable is easy to detect... is your clutch pedal soft and floppy or not? if it isn't , then it ain't the cable.

you can probably check the clutch arm on the tranny itself, you can reach it if you lay on your back, you'll see right away of the cable is broken or not...

[Blanco]

Mine did that once when I hadn't placed 1st gear in all the way. It was pretty loud too.

:dunno:

[FrayAdjacent911]

I drove my car 50miles home without a clutch. It can be done, but it wasn't fun, and hearing the gears grind while trying to rev-match made me grit my teeth. I'd have it towed if you can.

If it were the clutch cable, I would expect there would be slack in the pedal. Did the pedal drop a little bit? A lot? None at all?

[VaSteve]

Originally posted by FrayAdjacent911


If it were the clutch cable, I would expect there would be slack in the pedal.

Exactly. You could push it to the floor and it won't come back. I would look for something else as the problem.

[mjohnson]

Uh oh,

The clutch pedal feels like normal. Not floppy.
I'll try checking the connection at the clutch.

Not only is the car stranded far inside the gate here at work, but I'm 40 miles from any mechanic I'd trust with the car.

This is not good?

Mike
'78 SC

[osidak]

check to see if you dropped a cv joint -

I was going to say helper spring but you said the clutch pedal felt normal -

good luck

[JeremyD]

can you disengage the clutch pushing in the clutch pedal?

[dtw]

-Check the tunnel and see if perhaps the shift linkage came apart
-Check under the car and see if either of your halfshafts came unbolted from the output flanges on the transmission. This happened to me with similar noise and results.

[mjohnson]

An update...

I confirmed the normal movement and feel of the clutch pedal.

I reached under and checked what I think is the clutch cable at its attachment to the transmission. It seemed OK.

I confirmed that the car rolls freely with the gearbox in neutral, doesn't roll in gear. The car shifts into and out of gear as I'd expect to without the engine running. It makes all the right noises and it has the same feel.

I started the car, gearbox in neutral. All is normal.

I moved the shifter around gently, _barely_ towards first and it grinds as I'd expect it to. Same with reverse.

Then I realize, I haven't actually tried shifting the thing properly since it happened. So I give it a try...

Suprise! It shifts into first as it normally would.

I let out the clutch pedal slightly and it starts moving forward slightly as it normally would.

I let out the pedal more and it continues only moving forward slightly with no additional noise. Same behavoir in second gear, only it moves less. Same in reverse with some "rubbing" noise, no grinding.

Crap! Do I get to upgrade my clutch now? The tech article says it's only a 7 on a scale of 1-10. If PP has the parts kit for $900, I don't want to know what the out-the-door price at the shop is...

mike
'78SC

[JeremyD]

Maybe it just popped out of gear. I've had that happen on a 915 - made a pronounced pop as I touched the shifter.

[makaio]

In your last post you say you put it in gear and let it roll, but you don't say you've actually tried to drive it. If you haven't, I would try and drive it, so long as your sure the half shafts are still fully connected.

Like jaremy, I have had a 915 pop out of gear at speed and it made quite a racket, and made me loose my concentration while passing a mustang on the track.

[mjohnson]

More news! Not sure if it's better or worse...

The suggestion to check the axles was a great one!

The driver's side slides ~1/8" in and out with no clanks or other noise.

The passenger side slides ~1/4" in and out with a clank at the end of the outward pull. Oh, and I can swing it in a 1/2" arc with lots of clanking at the wheel.

Is this car safe to roll 1 mile? I'm guessing not, since if the shaft is disconnected from the wheel, the other shaft will be spinning the differential and causing problems. I have the factory LSD.

mike
'78 SC

[svandamme]

i'm sure it won't break anything that isn't broken allready
as long as it's just rolling , i'de say no problem, just don't pull it with a car at 50MPH...

[mjohnson]

Thanks to svandamme and others for the responses.

A phone call to the car's usual wrench got pretty much the same response. It was suggested that I tie up the axle to help prevent it moving too much while I tow it _slowly_ up the hill to freedom.

Then a flatbed ride home and a date with some jackstands, flashlights and a beer or two.

It looks like I'll get to buy that 200 ft# torque wrench I've always wanted...

Wish me luck!

mike
'78SC

[Miguel Antonett]

Something similar has happened to me when, for some reason or another, kept my hand on the knob while shifting from first to second with minor pressure towards second and the the gear just popped producing a scary sound followed by total inertia roll. Had the same feeling you have but after trying very gently to shift again everything was and is OK. P cars tranys are very strong...

[jcc911]

I too had a loud bang happen to me once while driving and I could not figure it out. The rest of the drive home was normal, as have been the rest of the Sunday drives.
Finally one day durning a random interior check, I noticed that my emergency/parking brake was no longer functional. I have not yet confirmed if this made the noise or if the cable is broken, but I would suspect that the cable had snapped somewhere.
Check your parking brake lever to see if it is functioning properly.

[indigowhale]

Sorry to chime in here, I had an identical BANG on my car when I thought the car was not all the way in first, put it back in and drove without incident. Next time it happened, just as loud, like someone threw a basketball at the car door very hard, the car would not stay in first. Had to limp home in 2nd. After trying to avoid the 915 nightmare, the reality came to pass. I had sheared most of the dog teeth on the the dog teeth gear off, so no first. Once you get the car home, you should at least check your drain plug for dog teeth. I am afraid everytime a bang happens on the 915s, a few teeth are coming off. Keep us updated.

[mjohnson]

I found out what the bang was...

The axle/outboard CV joint let loose from the wheel hub.

Well, that's what it looks like. I'm not sure what the real words would mean.

Axle's not broken, but I don't think I'm out of the woods. Pictures to follow soon...

mike '78SC

[Jim Sims]

Mike, There is a Porsche 911 community here in Los Alamos. I am one of them. I live in White Rock and work at the Lab. Let me know if you would like some help. If the outboard CV joint has just worked loose from the wheel hub it may be a simple matter to get it fixed (this could easily be a "parking lot repair"). Don't drive or push the car. There will also be a couple of 915 transmissions rebuilt in my garage over the next month or so if you'd like to observe or participate. Jim Sims