Muf

Hi,
I am experiencing a problem with my '79 911 SC targa.
It only happens when I try to accelerate quickly. When shifting from the first to the second, the teeth in my transmision clash. There is no other time they would clash. When shifting downwards or to any other gear, all seems fine. Even when I allow 1 second betwen the first and second, the sound isn't there. And it is not there also when I accelerate normally (ie the revs are not so high).

Is this a clear sign of a worn synchro ring on the second gear? Does it mean an engine+tranny removal and costly repair?
I am about to buy SWEPCO trans oil. Now I have a different oil brand. Can this help?

Thanks for any feedback.

Steve Weiner-Rennsport Systems

Muf:

Gear shifting clash is gnerally caused by:

1) Misadjusted (dragging) clutch

2) Worn syncros and operating sleeves

3) Wrong tranny oil (I recommend Swepco 75w-90) Never use any synthetic gear oil in any 915-equipped car.

BHMSC

Steve knows his stuff.

SWEPCO will help (especially if you currently have synthetic, as I didbefore I changed over) but, no matter what you do, it's still an antiquated 915 transmission and will never shift like a contemporary Japanese or German gearbox. Check the clutch adjustment, put the SWEPCO in, and take a little time on the 1-2 shift (both up and down).

Muf

OK, thanks, guys for your help.
I have recently changed the clutch cable and the helper spring and readjusted the clutch pedal. It did a LOT! Really.

So the next step is to put swepco in it...
Last year I put a new oil there and I think it was a synthetic one... I had trouble finding a swepco dealer in my neighbourhood so I decided to put that one in there. I think it was a BP or something...

I know that the 915 tranny will never be like the one in Honda S2000 :-) but it hurts me hear that horrible clashing sound!

Anyway, when I compare it to the way it shifted when I bought the car (March 2003) it is a big improvement. I reinstalled all the bushings, bought the short shift kit and renewed the transmission mounts (silentblocks). Every step was an improvement.

DGaunt

Darn right Steve knows his stuff!

Yes, the 915 is never going to snick, but it shouldn't crunch, except for first, where they only put 1/2 a synchro in.

According to the Porsche transmission course I took (offered briefly by Porsche Canada some time ago...) it is usually the operating sleeves, which are heavily machined, that fail rather than the solid, hard faced synchro rings. If you see the parts you'll know what I mean. The operating sleeves have a fraction of the material that the synchros have to wear off.

Glad to hear your other steps helped, but remember, every time it crunches you are damaging other expensive parts that eventually will have to be replaced too.

Muf

Believe me or not, the problem with clashing teeth disappeared with the newly poured Swepco 201 oil. I did not test it hard but with a normal test it seems to be perfectly quiet when upshifting from 1st to 2nd. And I even did not wait too long between the gears.

It seems that the synthetic oil is really NOT a choice for the 915 tranny.
Thanks guys for your help.
Muf