NineNine7

Hello all,

I just purchased a 50k mile 997 C4, 6mt. it's experiencing a rather strange issue that I can't quite pinpoint. Its got a slight grind upon entry of all forward gears except 1st. The car was recently inspected by a Porsche tech and said to have bad synchros.

I however, am not 100% convinced that it does. I've never heard of a car having equally worn synchros in 2nd,3rd,4th,5th,6th. Another strange (possibly unrelated) issue is that on two occasions I've depressed the clutch pedal to start the car and it didn't start, like it didn't recognize my big foot on the pedal. After jamming the pedal down in a moment of "thats odd" it started right up.

Has anyone had anything like this? I see lots of 1st gear jams, and 2nd grinds, but not all gears.

So far my research has landed me...

Possible stretched shift cable/out of adjustment
Possible spent/incorrect fluid. Change with PTX.
Possible worn synchros.

Sydneysixer

Hi NineNine7 - welcome to the forum. Some thoughts on possible actions, in no particular order:

Bleed the clutch slave cylinder, especially if you have recently had the brake fluid replaced, or was done shortly before you purchased the car (should be in the maintenance records). Trapped air could explain the clutch not consistently disengaging.

If that checks out, your car's failure to start on two occasions could be a faulty clutch switch (which detects when the pedal has been fully depressed) before allowing the starter to engage.

Replace the transmission fluid as you propose. I agree it is worth eliminating the more obvious/ cheaper options before concluding the synchro's on all gears are worn - I agree unlikely.

Please let us know what you find. This is a great forum to share experiences.

TommyV44

I bet it's the clutch switch!

Tom

Petza914

Under the car, check that the shift cables are properly snapped into the retainers. If they pop out, they won't control the shift action properly. Though mine have never popped out, I've wire tied them in so they can't.

NineNine7

Thanks for the warm welcome! I suspect that I'm an employee at our automotive group here (we have a Porsche dealer on the property) that much of the used car inspection process may have been rushed, and the fluids likely not changed. Because of this, I plan to do them all myself soon. The clutch switch is definitely going to get a look, as I suspect we're all pointing towards that for the starting issue.

I plan to give that a look too, while I think the technician may have noticed if they were failing near the mounting points he might have missed if they were stretched, or failing under the shifter box connection point.

semicycler

Some good advice here. You don't say what year your C4 is. A late model 997.2 is unlikely to have a gear oil problem. Early model 997.1 will probably see some improvement with a flush and fill. Likewise 997.2's have a recirculating slave cylinder so there's nothing to bleed. Do the symptoms change when the engine and tranny are up to full operating temps? How high off the ground does the clutch engage? Any change in clutch stiffness?

Echoing what others have said anyway - start with the cheap and easy stuff especially if you DIY the work. In no particular order:
- Bleeding slave cylinder, only applicable on 997.1's
- Verify shift cable ends are attached properly at the transmission
- Shift cable adjustment
- Gear oil flush & fill with PTX
- Replace the clutch switch
- Also check your engine and transmission mounts (easy to swap but not really on the cheap list)

If it still has problems then perhaps have the transmission dropped for repair work. While it's out have the clutch checked out and replaced if it's worn at all.

Bruce In Philly

Do the cheap easy stuff first, change the switch and replace the fluid. Easy. Then see what happens.

Clutch switch is an easy DIY although you have to be a bit of a contortionist and is about $40..... https://rennlist.com/forums/997-foru...placement.html

For the fluid, there are some DIYs outthere, I had my indy do it because I don't like getting under my car and I wanted the car level to ensure proper fill, but I supplied the Mobil PTX that was spec'd in my manual but not readily available. Lotsa threads on PTX, but use exactly what is recommended in your manual.

Peace
Bruce in Philly

NineNine7

I just realized I didn't specify, its a 997.1, a 2006 C4.

Thanks for all the advice guys, I think I've got a good game plan!

ehjun

i hate to bump old threads but this one keeps coming up in google searches.

i have a very similar issue. 997.1 C4S. light grinding unless i go super slow. some delay between turning the key and starting but never has it not started.

my symptoms do change when everything is up to temp. gear engagement gets smoother. clutch engages pretty high up so i feel like the clutch is not getting hung up.

ive done the cable alignment, and gear oil flush but i havent done the bleed. im going to try to do that this weekend. what is the likelihood that the bleed will fix the grinding?