Proper way of shifting the 915 gearbox - Page 2

Formerly Steve Wilkinson · 03-23-2005, 05:38 AM

Agree with all the comments about shifting deliberately and allowing the synchros to do their work, etc.,but one thing I have noticed is that when I let other people drive my SC--and frankly, any competent friend who wants to is welcome to, I enjoy introducing people to the Porsche experience--the fourth-to-fifith shift is one that must be done decisively. I don't mean rapidly, I just mean shifting as though you know exactly where the lever should move. People who are hesitant, not decisive, end up searching for fifith, and by that time it's too late, the gears have unmeshed (or whatever it is that happens), and they need to go back to fourth and try again.

Stephan

Formerly Steve Wilkinson · 03-23-2005, 05:39 AM

Agree with all the comments about shifting deliberately and allowing the synchros to do their work, etc.,but one thing I have noticed is that when I let other people drive my SC--and frankly, any competent friend who wants to is welcome to, I enjoy introducing people to the Porsche experience--the fourth-to-fifith shift is one that must be done decisively. I don't mean rapidly, I just mean shifting as though you know exactly where the lever should move. People who are hesitant, not decisive, end up searching for fifith, and by that time it's too late, the gears have unmeshed (or whatever it is that happens), and they need to go back to fourth and try again.

Stephan

wholberg · wholberg's Garage

Explain to the skeptical "friend" how syncros work.

Syncronizing gears accelerate or decelerate the clutch disk to match speed with the pressure plate. They do this through friction. Pausing betweeen shifts or applying light pressure to the next gear until it drops in extends the life of the syncro gear because maintains a better oil film, resulting in less metal to metal contact as that portion of the trannie catches up with the next gear. Ramming it into gear forces the surfaces together with more force, resulting in increased wear. Even the non-Porsche owning friend should understand this.

Just because his trannie is not worn out yet, does not mean it is not experienceing premature wear due to hard shifting.

DustinTarditi · DustinTarditi's Garage

Show your friend the comparitive pics of the fresh vs. worn synchros in the "101 Projects For Your 911" book - very illustrative.

Lothar · Lothar's Garage

When I had my in-car camera set up on the roll bar, I could see the shifter in my videos. Even when I thought I was shifting slowly and more gently, I was amazed at how fast I was actually shifting.

Subsequently, I moved the camera to the roll cage over the windshield. Out of sight...out of mind.

But really, if you think you are shifting fast, then you must really be tearing it up.

wholberg · wholberg's Garage

Dustin, I PM'ed you.

Barrpete · 03-23-2005, 08:59 AM

Having just bought my first 911 a month ago (I'm now addicted

) this is really helpful! It's an '86 Carrera with a 915 & 100k miles. I'd been thinking that since it shifts a little rough between 1 & 2 unless I pause a little, that the syncro was probably worn out and I might be looking at some serious repair bills. After reading this thread, now I'm changing my mind. It may still be a bit worn but might have lots more miles prior to major repair.

I think my wallet would be in a lot of trouble if it weren't for this site!

rcecale · rcecale's Garage

Quote:

Originally posted by Barrpete
I think my wallet would be in a lot of trouble if it weren't for this site!

HAH! Just wait til you do your first repair job on your own. Then your wallet WILL be in a lot of trouble BECAUSE of this site!

Welcome to the board, anyway! uh.....pics please!!!!!

Randy

Barrpete · 03-23-2005, 10:29 AM

Here's some pics. Nothing fancy, standard Carrera 3.2 but in very good shape. And you're right I've already found many things from Pelican parts to excercize my wallet - turbo tie rods to start. But at least I'll be able to pick some folks brains about what the $$ are spent on.

rcecale · rcecale's Garage

Nice lookin' ride! And, welcome, again!

Randy

304065 · 03-23-2005, 11:51 AM

Jack, wanna borrow a pair of my gloves?

no substitute · 03-23-2005, 11:53 AM

My '80 is one of the highest mileage cars on the board. It has had a bad (as in none) first gear synchro since I bought it in the late eighties. Still going strong. I grew up driving British non synchro first gear, sports cars, so the 911 is no problem. Try adding Swepco or your favorite fluid on a night with a full moon, and call it good.

84porsche · 84porsche's Garage

Quote:

Originally posted by 450knotOffice
Funny thing for me is that the 1-2 shift is normally very notchy (syncho issues, I know), yet if I do a redline 1-2 shift, the shift is smooth and effortless. It's like having two different trannies.

I know the feeling. The 1-2 shift is always the worst. I get a great take off in 1st and then a drop in power waiting to slide into 2nd. But after that 3, 4 and 5 are nearly perfect especially after the bushings and the short shift kit.

nabilious · 03-23-2005, 10:43 PM

Hey Derek - I have the same problem in a '72 right now and its not the first time either. all it takes is somebody to have really missed a gear going to 3rd and took some teeth off the syncro, after that, if you even try and shift during regular driving you'll get a "ziiiiipppp!!"
not your fault, but you'll have to slow that one down from now on or double clutch, cuz its always gonna do it. wait till another syncro starts to let go before you toss $1200 at a rebuild!!
Nabil

deoxford · 03-24-2005, 05:57 AM

Jack,
It looks like from your movie that it does shift very well at higher RMPs. IS that a true statement? My car seems to be hard to shift , well at lease to third if you are going slow. But get the rpm's back up before you shift and slides in. Fourth is hard to go it to all the time it seems.
What I am a taking from this thread is that a pause or doulbe clutch will fix that. I drove it doing that and there seems to be no differance.What are you thoughts on shifting this correctly, being that it may need to be babied for some time.
Thanks
Derek
Also; Great movie Thanks!

no substitute · 03-24-2005, 06:08 PM

New motor/trans mounts can help shifting.

nixter · 03-24-2005, 07:00 PM

Quote:

Originally posted by 450knotOffice
Funny thing for me is that the 1-2 shift is normally very notchy (syncho issues, I know), yet if I do a redline 1-2 shift, the shift is smooth and effortless. It's like having two different trannies.

I notice the EXACT same thing on my '80. Although instead of redlining everytime, a quick throttle blip during the neutral phase of the shift, (no serious pause required), will produce the same effortless result.

I guess those trannies like shifting at high rmp!

N

nixter · 03-24-2005, 07:10 PM

Quote:

Originally posted by Formerly Steve Wilkinson
Agree with all the comments about shifting deliberately and allowing the synchros to do their work, etc.,but one thing I have noticed is that when I let other people drive my SC--and frankly, any competent friend who wants to is welcome to, I enjoy introducing people to the Porsche experience--the fourth-to-fifith shift is one that must be done decisively. I don't mean rapidly, I just mean shifting as though you know exactly where the lever should move. People who are hesitant, not decisive, end up searching for fifith, and by that time it's too late, the gears have unmeshed (or whatever it is that happens), and they need to go back to fourth and try again.

Stephan

Interesting, I've "almost" found the opposite to be true. When I first started driving my car I found it very difficult to shift into fifth gear when trying to be precise about things, ie; up, over, up. Now, instead of pretending to know exactly where fifth is, I merely push forward from fourth gear with light pressure to the right and Bingo! Never a missed shift.

N

nixter · 03-24-2005, 07:15 PM

Has anybody noticed that if you make the 1-2 shift during a left turn that it goes like silk?? Must be a pressure thing.

N

geof33 · 03-24-2005, 08:32 PM

As all have said, 1-2 is always a tad notchy, but the reality is the rest of the box should be smooth and clean. As Jack said. My Trans has 100,000+ on it and it is still good, although my shift into 1st is getting to be a bit more notchy but is still good. It's all in the touch and feel of the trannie. Funny, my dad, who used to race a bit, got into my 911 after a few years of no manual driving and had NO problem at all. Didn't even kill it on the first shot.

So no fast shifting, but smooth and clean.