How hard would it be to design a smooth shifting, lightning quick gearbox .....
 

...... for a sports car like the Porsche that is similar in character to the slick shifting gear boxes on the Japanese sport bikes?

If you've ever ridden a Suzuki, Honda, Kaw or Yamaha sport bike, you know you can ratchet through the gears just as fast as you can shift em.... and they are bullet proof! ... you don't even have to use the clutch.

The car trannys could be designed to ratchet shift just like the bikes do, all that would be different would be making the gears more robust to handle the extra torque :cool:

Is there a reason this hasn't been tried before ?

Yes...no problem...these are straight cut geared boxes.
Dog shifters instead of syncro rings, nice wide gears, easy to shift.
Now for the bad part.....LOUD....NOISY....!
The gears will whine and the slop in the backlash will throw you from lane to lane in traffic.
Choose your design....streetable...or for the track.
Bob

Sequential shifters are out there.
In my opinion and I stress "my opinion" I believe that for the street, nothing beats the traditional H pattern.

If, while driving your car, you have to make an emergency stop then accelerate to get out of the way of an obsticle, you may have to ratchet from 5th or 6th gear 4 to 5 times before you reach 1st gear where as with an H pattern, you simply move the gear shift lever 1 time.

On a race course, "generally" you know when you're going to down shift prior to entering a corner and "generally" you're passing through the gears prior to and after the corner apex.

Under this kind of a scenario, I can see the advantage of a sequential shifter. (especially one that has a LED light that tells you which gear is engaged)

Secondly, more torque is not generated due to having a sequential shifter so if you're transaxle is stout enough for your existing engine torque/horsepower rating then it will stand up to a sequential shifter

Rather than torque from the engine, I think a greater problem would be higher shock loadings due to the increased weight of the rotating parts (clutch plate, flywheel, crank) compared to a bike.
In a sequential shifter such as on a bike, the rotating parts must change their rpm to match the new engine revs instantly as the dogs engage. If you dip the clutch, this means the clutch plate (if you don't, then this also includes the flywheel and crank) must be accelerated/slowed instantaneously by the dog system. They're gonna have to be beefy dogs!
Probably not impossible, though.

That's a good point. I know the flywheel, crank and piston assy. on my Yamaha R6 is super light, as fast as that thing revs.

If I was in the design business, I would have to try something like that out. The only big disappointment with my Porsche is how poorly it shifts.

Mendeola makes sequential transaxles.

Compared to designing a gearbox, manufacturing one that meets all those criteria would be a challenge, to say the least. How many would be produced and at what cost?

I understand WRC sequential gearboxes are on the order of $25,000+. How hard can it be to design a gearbox?

Yes, it can be done. Be my guest.

Sherwood

As Hewland has said:
http://www.hewland.com/svga/faq_answer_4.htm

:(


I'm only smart enough to ask the questions.

The 911 has been around forever. Seems there has been market for a better transmission for quite a while. The G50 was an improvment, but I had an 87 Carrera and didn't think it was all that great .... maybe because I grew up on hurst shifted Muncie 4 speeds, I expected at least the same performance out of a high end car like a Porsche.

I am just trying to get used to the beastly shifting 930 4 speed, and started wondering why they seem so behind the times.

Do the road rally Porsche guys run stock transmissions as a general rule, or are they heavily modified / special design?

Any pre G50 911 would be greatly improved by "slick shifting gear boxes on the Japanese" '80s economy cars. It always amazed me that a old rwd Toyota Corolla could have such light, short and precise throws.

For what it's worth, the reviews of earlier 911's often singled out the 901/915 for particular praise. Then the Japanese came along and built a smoother mousetrap. But in some ways, we're comparing apples to oranges; a Corolla or a bike isn't (usually) running a whole lot of torque through its drivetrain.

The 915 is especially susceptible to bad maintenance and age. A lot of the complaints about it come from boxes that are long overdue for a rebuild, with shifters out of adjustment and bushings that are rotted and stretched.

sequential gearboxes are more compact, high speed, relatively low torque, and overall more fragile than H-pattern gearboxes. Their advantages would only be available at very high $ cost in a package suitable for a modern 911 transaxle.

IN your present system: If your shift linkage and your clutch adjustment are not perfectly spot on in adjustment, you have not seen the best that your present transaxle can provide.
I have a early (7:31) 915 transaxle mated to an 87 3.2L engine in an early targa. Until a few weeks ago, I also hated my trans, dreading every attempt to get into 5th, or back into 4th from 5th. Difficulty finding the proper gear (is that 4th? 2nd? oh shiiiii...) and all of that.
Linkage wise: I stripped everything out that I could get my hands on, put in a new front bushing, new WEVO shift coupler, and a new Rennline shifter (mine was worn in so many areas that I chose Rennilne over WEVO so as not to need any of my old shifter parts.)
The difference is amazing. It is still not a light speedshifting box, of course. But every shift is precise, there is NO unwanted slop in the mechanism anywhere. I know exactly what gear I am in at all times, and I enjoy shifting again. Well worth the investment, IMHO.

Maxx1..interesting. my Bday is 3/3 as well and my main interests are guitars, motorcycles and cars ! anyway, ive thought about this also but, have come to enjoy my 915 transmission. I like the involvement and having to learn how to shift it properly. It makes it more fun, to me. I certainly would not want to have to worry about shifting on my bike. too dangerous as it is. The 911 is different. Ive driven newer sports cars with super smooth shifting transmissions and a soft clutch and found them terribly boring

perhaps your transmission is not set up properly or needs repair.

"reviews of earlier 911's often singled out the 901/915 for particular praise."
---------------

The [newly introduced 911’s] 5 speed gearbox is probably the new car’s best single feature.” – CAR & DRIVER, April 1965, p. 30.

The gear “lever remains delightful to use…” Motor, Jan. 29, 1972

The 901 transmission is a “superb five-speed gearbox… provides a ratio for every occasion…[and] requires so little physical effort that winding up and down through all five ratios… when pressing on in twisty or hilly country, is one of the most rewarding pleasures in motoring.”
-- Motor, Feb. 8, 1969

The 901 transmission “gate [is] well-defined.. and the powerful synchromesh is so utterly smooth and unobtrusive that the lever seems hardly to be attached to any mechanism. Upper changes are made as fast as the lever can be sliced through the gate….”
-- Motor, Feb. 8, 1969

The gear lever “movement is so natural, if you try to change across the gate, you’ll muff the shift.” “When other manufacturers want to [brag] their specifications often list Porsche-type baulk-ring synchromesh. The yardstick is Porsche and Porsche gear syncronisation is perfection.”
-- Wheels, July, 1969

The five speed, all synchromesh gearbox is one of this Porsche [911’s] greatest delights; it is light to operate and I find it almost impossible to change too quickly.”
-- Motor Sport, Jan. 1970

You -- and those reviewers -- said it much better than me. ;)

But it's safe to say that they don't age as well as the 911's engine or suspension. In the years since, we've all gotten used to pretty-much maintenance free transmissions.

Absolutely true. Let me re-quote your sage words, Jack -- w/just a little editing...


A lot of the complaints about [Porsche transmissions] come from boxes that are:

[1] long overdue for a rebuild,

[2] with shifters out of adjustment and

[3] bushings that are rotted and stretched.

----------------------------------------------------

I can't recall how many times somebody has complained and then had a Eureka moment after doing one or more of the above. Obviously don't do them in that order, unless you KNOW the gears/synchros are worn.

The main problem I'm having with mine is getting it to go into first after stopping at a light. I'll double clutch, I'll shift from second and then try to go into first, sometimes in my hast I'll hit reverse ..... all the time feeling like a dope if there are cars waiting behind me.

I had a 106K mile 87 Carrera and more recently a Boxster S, both were better shifting than this 4 speed is.

Sounds like I need to look into checking the bushings and getting a rebuild kit.

Acura's weren't invented yet ;)


I think it's a matter of the shift linkage gets worn rather quickly and out of alignment.

to get into 1st easily, shift into 2nd - wait a sec. - then shift into 1st

Maxx1,
I recently replaced the shifter bushings ($7) and the coupler ($80 factory OEM) in my '86 915 (60K miles) per the sage advice of the members of this board. When I took everything apart, nothing was obviously worn out so I thought I was not going to see any real difference and a tranny rebuild was in my immediate future. The bushings didn't look too bad and the old coupler had a little more slop than the new one, but nothing real bad. After a couple of subtle adjustments to the coupler position to get everything lined up, I took the car out for a spin. Holy *****! What a difference. If I was blindfolded I would have thought I was in a different car.
Expect for the passenger seat not wanting to be taken out, and my wifes insistance that all the carpets must be cleaned, this is a real easy job and could make a big difference in your driving pleasure. Order the parts.

+1 for worn bushings. After replacement, 1st and 2nd are still resistant, but shifting is much more precise.

Not that this will resolve your current problem, but I rode in a 930 with an SC 8.31 r/p 915 gearbox, and the car felt extremely fast. You could consider picking up a used later 915 box that's been recently rebuilt. By that point, all the shifting problems you now experience should be eradicated.

and speaking of gearboxes probably in need of a rebuild.. :rolleyes:

is yours holding together Jack?

I had a full rebuild ++ built around a 3.4L future install.

glad i went that way instead of a G-50

I have never driven with one but... my guess is that if you could get a WEVO dog box, it would be the cat's pajamas. I have raced against them, and they are advantageous compared to a normal 915. But it will cost you. Not sure whether they are available any more as new though.

Another approach was taken by one of our local racers... he rigged up an EMCO (used in DP cars). Not cheap.

Anothe route is to just buy a modern Porsche factory race car and put the parts in your street car. Maybe not practical.

:eek:

Yep, guitars and cars and wheelin down that long lonesome highway ! SmileWavy


Sounds like from everyone's advice that a bushing kit is money well spent. I forgot to mention, 3rd gear is kind of funky to find at times as well.

Why are you "hasty" shifting into first? Even with my G50, I'll gingerly slip my car into first while coming to a stop (or stopped), and then back into neutral while waiting for the light to change. I also tend to watch the opposing traffic & lights, and usually anticipate my green light, and shift back into first a second before the light changes. Even if I don't anticipate, she shifts easily back into first with this technique (1st > neutral > 1st), maybe it'll work for you for now.

Another comment about non-sycnchro transmissions whether sequential or not: most of them are racing oriented and therefore close ratio, so less difference in gear speeds during shifts and less 'need' for synchros.

I remember the first drive I had in a '79 SC in about '80 or '81, so a pretty new car. I could not believe how nicely it shifted, I came out of british stuff which shifts pretty nicely, but even if the 911 had longer throws than my MGB, it just had a beautiful feel. I remember shifting it just to feel it. I also remember mid '80s BMWs having very slick feel.

Or just go directly to this and be done with it!
:D

http://hargettprecision.com/index.php?cPath=35


http://forums.pelicanparts.com/uploa...1184764456.jpg

Also, replace your tranny and engine mounts, perhaps with sprotier versions. Keeping everything lined up with the linkage made a big difference for me!

Good discussion.

A feature of a sequential transmission (like a bike) is you CAN’T skip gears. This means every gear change has minimum rpm difference. With only slight power interruption (many use an ignition/fuel interruption system), there doesn’t even have to be de-clutching or lifting on the throttle.

I agree about straight cut gears, they are too noisy for normal street use. The choice of straight cut gears (noisy but strong) compared to the various angle cut gear forms doesn’t have anything to do with the choice of engagement (dog, syncro, etc.)

Some later G50 types (G64 …Japanese G97/01) have changed the syncro angle (to 15°) to reduce the effectiveness and allowing faster (sequential) shifting. I understand some electric systems have 2 mS shifting.

I think the auto industry is going away from automatic transmissions with clutches, planetary gears and torque converters. It seems the choice is regular mechanical transmissions (10+ speeds), dog engagement (no syncros), electric shifting (sub-millisecond) and all computer controlled. I think the reason is fuel efficiency and emissions - AND it gets everything under the control of the computer.

I think the RS Spyder may lead here.

Best,
Grady

I agree Grady. The systems with 2 clutches, such as the VW DSG tranny, with one always engaged is appears to be the future of transmissions.

http://en.wikipedia.org/wiki/Dual-clutch_gearbox

Helical dogboxes are popular with the Subaru crowd. Quiet for cruising at the cost of some gear strength, but fast shifting.