Sequential Transmissions
 

I've searched, but couldn't find much about sequential transmissions for 944's, so I have 4 simple questions: why are they so expensive? Does anyone make an affordable sequential transmission for the 944? Why are they so noisy? Why do they require frequent rebuilds? I think it would be pretty bad ass to have a sequential transmission in my car...

A sequential trans is like a motorcycle trans., it shifts linearly.
I have seen a website that shows sequential transaxles for the racing Porsches. Never seen one for a 944 pr 968, although they are similar in design.
I would imagine they require frequent rebuilds due to their application, which is normally racing.

Forget that, I want a PDK!

i installed one into my ls7 944 it's a quaife 6 speed sequential .
they do not make them for the 944's for what i paid for the gear box you can go buy your self 2 944's or a mint 968 .
they are designed for racing if you think you will be driving it on the street for get it ! that would be total hell .
once your moving the clutch is not used at all just leave your foot in it and pull up into the next gear .
down gearing is a little deferent but the same thing very little rev matching is ever needed .
this past weekend i was working on the paddle shifters for the car .

hey requaire far less maintenance that your standered type of road trans .
just keep the oil changed in them .

they are loud because they have what are called straight cut gears in them . the gears in your street trans has the gears cut on a angle . but by doing so you can't shift with out using a clutch . this is becaus eyou need to releace the pressure from the gears for them to disingage and ingage into the next gear .

the are costly for many reasons . the 1st is they are hand built gear boxes . then your picking the gearing you want from 1st to 6th final drive too your having custom build you a gear box there is nothing off the shelf about them .

Are they really that bad on the street? Not having to rev match when I downshift seems like a godsend to me. If I didn't use it for racing, would it last longer? Are they deafeningly loud or do they just make an annoying noise? Pulling/pushing a lever to shift instead of having to move it in a complex pattern seems awesome to me.

false

the helical gears of a standard transmission do not engage and disengage when the shifter is moved, or the clutch is used. the helical gears always remain in contact for all gears at all times. the shifter connects and disconnects the syncros, not the gears themselves.

and false that straight cut gears are required or necessary in a sequential transmission. depending on the type of sequential transmission, the straight cut parts are the dogs for the gear. again, this is what is actually being engaged when shifting, not the gears for power transfer.

Lol he just told you, not only do they have huge drawback for street use but for the price of one of those sesquential tranny you could buy yourself a couple off 944s plus a 968.Very few peoples here will be able to afford such a tranny for a street driven car,it wouldn't make any sense .:eek:

Complex pattern? Come on dude it's not even a six-speed :)

This is what straight-cut gears sound like: Straight Cut Gears - YouTube

You'd be a damn fool to run them on the street.

they are not in any way good for the street !!!
if you looked at the link on youtube you will have about a 10th of how loud they really are .
the harmonics in the fiberglass helmets make it worse the cabon fiber ones are just a little better but thats pretty much all you hear .
the exhaust is the other thing the noise out of the LS7 with the pipes running down the spot were the right side floor was is the other thing .
after a 2 hour stint your ears are ringing then by the time you all finished with the 24 hour event your ears will ring for the next two days .
it will be good when i finish the paddle shifters holding 12 " wide front tires with one hand as your shifting beats the crap out of you .

the noise your hearing is coming from the way the gears are cut (straight ) and meshing together .
my sports racer does the same thing it too has a 6 speed sequential gear box in it .
gear boxes differ just like LSD's do there are many types of both and they all have there own sound to them . I changed out the wedge lock in my sports racer to a triple lock you still hear the whine of the gears but now you also hear the diff more too .
now don't get me wrong ! i never stated that all sequentail gear boxes have straight cut gears . but the whine you hear like in the video is just about the same whine you hear in my cars they are coming from the gears and diff .

it's not just the cost of the gearboxes thats the bad part because all and all they are only about 9 to 12 K it's all the other crap that you have to also buy and do .

I'm sure I could afford one if I pick up a few people's shifts at work :D

I was just kidding. I couldn't think of a better way to compare the push/pull shifting of a sequential transmission to the way you have to move the lever around on a manual.

Damn, that hurts my ears! If motorcycle transmissions are sequential, why don't they whine like that? My old Hodaka Road Toad and CRF150 didn't make any funky noises.

What else would I need to buy? I'm assuming I need the shift linkage.

Actually, it's perfectly possible to shift a transmission with helical gears without using a clutch. You simply have to rev-match near-perfectly. However, the synchros and blocker rings make it exceptionally difficult and place great strain on the shift forks, so it is not recommended. This is because the synchro mechanism actually incorporates a blocker to physically prevent the dog teeth from engaging unless their speeds are synchronized. However, there are lots of non-synchro transmissions with helical cut gears (OTR semis and motorcycles come readily to mind) where shifting without a clutch is the regular mode of operation even with helical gears.

Synchros do not "connect" or "disconnect." They merely provide an amount of friction force to allow the dog teeth to engage smoothly. The synchros themselves have absolutely nothing whatsoever to do with coupling the gears to their respective shafts; all the synchros do is smooth the engagement of the dog teeth. Most synchro systems also employ some form of blocker to prevent contact between the dog teeth until the synchros have done their job and matched the rotational speeds.

On a general note, helical-cut gears are physically stronger than straight-cut gears as well as quieter. The benefit of straight-cut gears is that they allow "crash box" transmissions (transmissions where the shifting is done by engaging the gears themselves and not by engaging and disengaging dog teeth) and they are cheaper and easier to manufacture. When dealing with a racing transmission that is less likely to be expected to last 200,000+ miles and where the ability to use custom-cut ratios for different tracks is important, straight-cut gears have an advantage.

You still have to rev-match on a downshift with a sequential transmission unless you want to jerk the ever-loving ***** out of the car when you re-engage the clutch. Rev-matching is NOT the same as double-clutching; rev-matching means that you bring the engine close to the right RPM before re-engaging the clutch after a shift has been completed. This is necessary for smooth driving regardless of whether you have a sequential gearbox or a standard H-pattern box. While a sequential gearbox will eliminate double clutching between gears, it will NOT remove the need to rev-match to make a smooth downshift (any motorcycle rider can tell you this).

I meant downshift rev matching, not double clutching. I'm not exactly a pro at rev matching for downshifts. I can get it close enough that I don't have to drag the clutch to make it smooth or have the car lurch like crazy, but it's not as smooth as I would like. I guess a sequential transmission wont solve this problem :(

I don't know why, but I really feel like I have a knack for this naturally. When I first heard of it on this forum I drove and tried it a couple times, after a handful of tries I was landing the correct RPM almost every time. Now it seems almost effortless :eek:

Price for sequential transaxle transmissions start at about $25k. They measure longevity between rebuilds in hours, not miles. They represent a great advantage on the track but there would be less than a handful of people on the planet that could realistically even consider running one in a 944/951. Most of these cars are owned by young US students who don't have anywhere near the $$ to explore this level of customisation. Remember, it's not just the cost of purchasing the gearbox, you have to cut the car up a lot and custom fit it. Then there's custom axles, CVs and probably a fuel cell. You'd be over $30k before you blinked....sad to say.

Something like this could probably be adapted to work with the 968 trans with enough time and money..

http://www.sqsracing.com/produkt/354:449:sqs-e-sqs-g-audi-quattro-01e

The 968s gearbox is basically the same as an 01E and many parts are interchangeable.

My old Hodaka Road Toad and CRF150 didn't make any funky noises.



Oooh, Hodaka, haven't heard that name in a number of years. Had a Hodaka Combat Wombat, back in the, cough, '70s. Just the name alone scared off little kids. The tranny was made of glass though.

you are correct, i only use sychro because its basically the same part. the synchros engage, mate up, and then the dogs match up slip together and transfer the torque.

the reason why your not getting the whine out of most motorcycle gear boxes is just in the desing of them . yes they too have straight cut gears .
i my younger days i raced motorcycles for many years . you do not rev match to down gear many motorcycles . you can and do at times and the same goes for sequential gear boxes in cars .
what i have been doing now is installing a little computer in the car that is for the the trans .
what it does is as you go and change gears it dropps the voltage on the motor to still keep it running but drops it fast enough and for long enough to change gears at any time with out ever needing the clutch but just to get going and to come to a full stop .

because this gear box was designed to work a deferent way and we took it and turned it around and flipped it up side down .we had to have the internals reworked for the fill and drain plus , oil cooler feed and return lines and just to keep it properly lubed .
so there was another 3K FOR THAT .

then there is the tork tube and drive shaft . that needed to be totaly custom built we took two belhousings one for the LS7 motor and one from a 996 and then after doing the fab work we needed to do send it out and have a drive shaft built for mateing the two together .
there was another 3200 dollars for that in parts and labor and that does not include our labor .

then the half shafts . i'm using a 996 rear suspension front also . so to keep the track of the car the same as the 944 the half shafts have to be built for the lenght needed .
so i'm there any way i just had them install bigger and better CV's also .
add in another 1900 dollars for that .

then the car is a tube chassis car with all carbon and fiberglass body panels .
add in the cost of all the materails to get the gear box in the car and working .
my guess would be about 1200 dollars .

then the paddle shifters and the computer and gauge for the trans it tells you what gear your in and the oil temp of the trans gear oil .
there is 9K into that right now .
because the computers are deferent for the one with the stick on the floor to the one i need for the paddle shifters i maybe able to sell it ? and get some money back .

now with out the computer to drop the motor power just a little you still don't have to rev match to down gear all you do is lift your foot off the gas for a split second on each down gear and never on any up gears .

Wrong.

My 2007 Harley XL1200R use helical cut gears. Harley's 6-speed transmissions on its big twin motorcycles are also helical cut, constant-mesh units.

Most motorcycle sequential units are, in fact, helical constant-mesh units with dog-teeth engagement. They are non-synchro, but they are absolutely not straight cut.