Proper way of shifting the 915 gearbox
 

What is the proper way of shifting the 915 gearbox?

A friend (non-Porsche owner) claims that if you shift any gearbox quickly and without detecting any grinding or resistance, then no damage or premature wear will result from that style of shifting.

My proposal of pausing slightly in neutral between shifting into the next gear was met with derision and disbelief. He thinks I am crazy to claim that if one doesn't pause as I suggested, then no damage will still occur to the gearbox.

Haven't anyone heard Bruce Anderson describe how many factory racers were told to pause between shifting to make the 915 gearboxes last the race?

Your real world experience is needed to win this disagreement.:mad:

Sorry a correction to say " that if one doesn't pause between shifting then damage (or premature wear out of the synchros) will occur.

Does your friend know how expensive these babies are to rebuild?
I learned the hard way, my friend. I beat the crap out of mine and it took it's toll on second gear. As discussed here before, these cars are not meant to be drag raced. For longevity, it is best to pause between shifts with the 915 trans.

I don't exactly pause, but the 1-2 shift is quite sluggish and should not be forced. There's a brief interrupt in the motion just before it drops into second. Maybe that qualifies as a pause. It's more like babying it into gear.

Gears 3 through 5 are much faster shifts.

POWERSHIFT! YEAH! 915 rebulders need the jobs...;)

I think "deliberate" is a better term than to say I pause between gears. The stick doesn't stop moving, it just a slower methodical movement.

I have on occasion managed to chirp 2nd gear when the need arose, but that was only when necessary. ;)

Having been poor in my young days and having spent a lot of time working on equipment, I'm very kind to vehicles. I not only pause, at times I "double-clutch" to be kinder yet. What's just as important is how one down-shifts a 915....The 2nd to 1st shift is critical....Do it slowly and deliberately....If it doesn't want to go into 1st, don't force it. Go to netural, let the clutch out briefly, then to 2nd and then 1st...I've had my '73.5 since 1990....It shifted great when I got it and it shifts great now....Did finally change the shift bushings though.....

It's a finesse thing, and I'll bet that most 915s require a different touch. After shelling out some serious $$$ for a rebuild, I make a nice smooth and deliberate (not hasty) change between gears...no matter what.

I am still new and still learning these Porsches, So this is helpful...
I found that just normal shifting with maybe a pause is still rough going in to second and third.

SO Now I pause still maybe, and keep the RPm at about 2500 and it seems to shift like a dream.

Am I doing this wrong?

Here a shot of the car

http://forums.pelicanparts.com/uploa...1111554047.jpg

Derek - You might have a syncro going south on that 2nd to 3rd shift....Try double-clutching....Go from 2nd to netural, let the clutch out briefly, put it back in and then go to 3rd......Just like in the old days in the 30's and 40's when they didn't have syncros.....(No, I'm not all that old).........

1-2 and 2-1 might need a moment of hesitation, but beyond that, a properly set-up 915 is pretty sweet.

Ok, so Am I supposed to pause between 1st and 2nd then 2nd and 3rd? Is what I doing tearing it up?

The greatest wear on trannies, (IMHO, is from 1st to 2nd, especially when they're cold in the morning). Most old trannies have wear on these two gears because of that shift.

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. :rolleyes:

Well my obstinate friend wants evidence that improper forcing shifts result in damage to gearbox even if no grinding is heard. Anyone has evidence to post showing him the damage from rushing a baulky box?

His argument is he shifts quickly in his Acura Integra and Nissan 300 ZX Turbo and they have not exhibited any worn synchros or gearbox wear. I told him he's comparing different designs and the Japanese boxes are much easier to engage shifts without problems. Sop he insists that he should continue to shift fast even when driving a 915 tranny and I said that's where it won't be my cars that will get abused.

Just don't let him drive your car- simple as that :)

Sometimes you can shift them fairly fast, it just depends on the speed and load on the spinning parts. The important thing is to never force it, but if it just "drops into" the next gear, then quick is OK.

Best advice, (or technique really), that I have heard was from Tyson Schmidt when he said that w/ the 915 it's "quick foot/slow hand". Takes a little practice to get that down in excited driving situations, but that is the long and short of it. :cool:

Rhythm and timing. Theres a spot in the RPM's where the gears will just drop into place going up or down in speed, find it and the 915 is happiest. Develope a rhythm to your momentum and it's like sweet music.

Your friend sounds like he may not be thinking clearly for one reason or another.

Proper shiftin of 915:

- Press accellerator pedal until middle instrument goes into red
- Depress clutch and try to upshift
- Listen for familiar *CRUNCH* -sound
- Try to shift into another gear, when it doesn't work just apply harder pressure on shift-lever
- Repeat until you either get tired and swap it for G50 or convince yourself that it's just "part of the charm"

Alternative:

- Depress the clutch
- Move lever to neutral
- Release the clutch
- Depress the clutch again
- Move the lever to chosen gear, carefully matching the revs to avoid crunching the gears too much
- Release the clutch

:D :D