968 6 Speed VS 951 Transmission

Hi All,

I'm currently running a 968 6 Speed Transmission with my LS6 Conversion, with this transmission my 1st and 2nd gear are almost useless. Has anyone gone from a 6 speed to a 5 speed and seen any benefits? I know the ration even out as you get to 4th,5th and 6th, the 968 transmission also is quite strong.

My 968 isn't fully together yet, but I had a ls1 swapped turbo car with the LSD 5 Speed that I will be using in the 968 along with the 951/944 torque tube, and cv shafts. From everyone I have talked to the 5 speed trans is stronger than the 6 speed, and the gear ratios are a lot better for a v8.

LS968 wrote:My 968 isn't fully together yet, but I had a ls1 swapped turbo car with the LSD 5 Speed that I will be using in the 968 along with the 951/944 torque tube, and cv shafts. From everyone I have talked to the 5 speed trans is stronger than the 6 speed, and the gear ratios are a lot better for a v8.

I don't think its an issue of strength but the taller gears and lower axle ratio, they way my car pulls form 4th to 6th is nothing like 1st, 2nd or 3rd. I do like the 6 speed but am thinking of looking for a turbo transmission over the winter.

Thanks!!

You might want to talk with Allen (Odurandina) from rennlist. He had a taller R&P installed down in Houston. I think the 951 trans is still the better choice for ratios. 25.75 " O.D. rear tires are the sweet spot.

Hey Another question I'm wondering. Did you have to put the 944 Driveshaft in the 968 Tube to make it work?

xschop wrote:You might want to talk with Allen (Odurandina) from rennlist. He had a taller R&P installed down in Houston. I think the 951 trans is still the better choice for ratios. 25.75 " O.D. rear tires are the sweet spot.

Hey Another question I'm wondering. Did you have to put the 944 Driveshaft in the 968 Tube to make it work?

ok, ill look him up!!

i have the 968 transmission bolted up to a 944 Tube, i'm not using a 968 tube.

Thanks!!

I'd love a 6 speed transmission with the same turbo 1-5, then a true over drive 6th that would drop cruising rpm another 1000 rpm. So kinda like the corvette ratios.

docwyte wrote:I'd love a 6 speed transmission with the same turbo 1-5, then a true over drive 6th that would drop cruising rpm another 1000 rpm. So kinda like the corvette ratios.

Yes, that would be ideal!!

So what you want is the 968 Turbo S tranny.

Dawgz83948 wrote:So what you want is the 968 Turbo S tranny.

Yes, I found the following thread that talks about gear ratio differences.

http://forums.rennlist.com/rennforums/968-forum/550016-968-turbo-s-for-sale-3.html

I'm not sure if this is common to my setup but transmission ratios seems to be a an issue when it comes to getting V8 HP/Torque to the ground, the mere fact that the stock transmissions are designed for turbocharged motors (Higher RPM/Power band) shows a discrepancy. I must say the 968 transmission is good for drag racing with a big cam!! if things don't break!!

If you arn't worried about cost, you could look at Albins Gear. They will even make special ratios for you.

http://www.albinsgear.com.au/products_manufacturer.php

Any idea on ball park prices for those custom Albins gearsets? You can start here - 4 figures or 5

the 968 gearboxes have been run up to 700+ hp without failures... but not only is 1st gear too low, they're all basically "in between" gears.... in this post i'm going to be assuming that we're running a larger tire -- like a 275-35-18 (25.6" diameter tire)... two very good tire sizes for v8 swap cars are 275-35-18 or 285-35-18 such as XSChop and myself are both running.

here, the fix would be a taller R&P in the range of about 2.70~2.85:1... i have had numerous conversations with Roger at California Motorsports (CMS) in Lake Havasu, AZ who in turn, has consulted with Albins Gear several times... after doing the research Albins determined that only a 3.00 or 3.10 R&P can be manufactured that will get close to the ideal "2.85:1" ratio for a street car... other gearsets including a 3.400 or 3.446 (the 968 Turbo S ratio) for a track/drag/street car can be made up. *(the 3.0 is the lowest R&P that is close to ideal but can still be set up for the 968 box).... the cost for one-off gearsets purchased through Roger are about $4,000. not bad considering....

either of these available ratios is a better choice for a high torque/hp V8 (than the stock 3.78 ratio) for making gears 1-6 more useful.... and installing one of these combos (i believe the 3.1) results in a similar sequence as you have with 1-4 on the 944T box... however, i just couldn't see doing it. and not because of the cost ($4,000) but rather, because the final ratios of 5th and 6th still wouldn't end up being high enough for everyday driving... considering my investment in a new LS3 is fairly enormous, my rpms on the faster secondary roads and slower state highways wouldn't be low enough to make maximum use of 5th gear, and my rpms between 65 and 100 mph on (interstate highways) wouldn't be cut down low enough in 6th gear....

hats off to Roger at CMS who first pointed out to me the importance of not just changing 6th gear but 5th as well, and he was absolutely right. not having the right gear for driving in traffic between 40 and 60 mph would really suck. and the 968 box's 5th really isn't up it....

after consulting with another Audi transmission expert (Scott Dewitt owner of Advanced Automotion in Corpus Christi, TX), i learned that what we need are 5th or 6th gearset options out of the Euro 2wd A4 diesel transmission... but, because the 2wd 01E never came to USA or Canada so you cannot source 01E 2WD gears through audi's North American parts distribution network. some (myself included )have erroneously stated that the .680 6th gears found in many of the Audi A4 and S4 gearboxes over hear in the states will fit the 968 gearbox. not so !! these are of the 4WD variety, and will not fit any of the 2WD 01E's, and therefore not fit the 968 box... the 2WD box and 4WD gearbox share the same input shaft, 1-2 gears, diff carrier, diff case, and center housing, and even their rebuild kits are 90% compatable... however most everything else is different.

first, i located a transmission with only 48 k miles just 14 miles from my house. win... running the stock R&P and with 1 through 4 this will remain a compromise... next, my first choice for 5th gear would have been something between about .770 and .820.. but the closed gear that will fit is a .729 5th...... for the high hp i'll be running, the ideal 6th gear would be about .620.... but a .600 6th gear came with the euro A4 diesel for the win...

the next problem is the gap between 4th and 5th... and this presents a compromise.... but since i'll be running a 480+ hp engine with huge torque, i'll only need to run the rpm up in 4th a bit higher than ideal before switching to 5th... and even if i was blowing someone's doors on the street, i'd only needo to go a bit higher still, in 4th and still have the car north of 4500 rpm after switching to 5th.... so it's all that torque that solves the 'gear gap' problem for any street driving and you're better off with that gap happening after 4th gear imo, than having it happen after 5th when the car's horsepower demands are considerably higher..... but the payoff is really there once you experience the utility of having that tall 5th gear for cruising in traffic or running the secondary roads without premature wear on your bores, rings and bearings....

the problem of 1-4 still remains but in 5th and 6th, you're close to perfect...

let's run some numbers.... first, there's a considerable variance on speeds depending on what tires you run. i'm gonna float some numbers using a tire that's fairly close to the limit of what you'd ever want to have back there... my 25.6" Dunlop 275-35-18s. running the 35 aspect ratio not only gives me a little more gear in 1st and 2nd, but the ride is a lot less harsh.

stock 968 transmission;

1st; 3.182 :1
2nd; 2.000 :1
3rd; 1.435 :1
4th; 1.111 :1
5th; 0.912 :1
6th. 0.778 :1
final ratio 3.778

968 transmission with audi 2wd diesel 5th and 6th;

1st; 3.182 :1
2nd; 2.000 :1
3rd; 1.435 :1
4th; 1.111 :1
5th; 0.729 :1 (gap between 4th and 5th)
6th. 0.600 :1
final ratio 3.778

stock 968 gears w/ Turbo S R&P;
1st; 3.182 :1
2nd; 2.000 :1
3rd; 1.435 :1
4th; 1.111 :1
5th; 0.912 :1
6th. 0.778 :1
final ratio 3.446

bear in mind that whatever tire combination you run with a stock 968 transmission, your top speed in 4th gear will be about 82 % of your top speed in 5th gear.... top speed in 5th gear will be about 85 % of your top speed in 6th gear. my top speed running 25.6" tires in 4th gear is 113.8 mph @ 6,500 rpm... 5th gear (stock form) is 138.3.mph at 6,500 rpm, or 85.3 % of top speed in 6th gear.

my top speed running 25.6" tires and the stock transmission would be about 163 mph @ 6,500 rpm. in my case, my engine will be governed at 6,300 rpm so i wouldn't even be doing that good....


fitting taller gears; some numbers....

starting with the 5th gear, changing to from .912 to an available .729 01e diesel 2wd gear will make 172.9 mph at 6,500 rpm for your cars and make 160.0 mph if you were switching to 6th gear at 6,000 rpm....

running this large tire with a 0.600 6th gear would allow you to be able to reach 190 mph @ 5880 rpm and upwards of 195 mph @ 6035 rpm (stout LS2 or 3 with a cam).... and 200 mph @ 6189 rpm (could be possible w/ more head work and NO2).

now for running Turbo S, 3.44 diff.... ok, just multiply all the speeds listed above by 1.0934877 (3.778/3.446)

top speed running 25.6" tires in 4th gear would increase speed to 124.4 mph @ 6,500 rpm... very nice. top speed in 5th gear increases to 151.2 mph at 6,500 rpm, and top speed in 6th gear goes up to 177.3 mph at 6,500 rpm.... however, the plot thickens because the Turbo S box came with taller 5th and 6th gears (although sourcing these gears will be next to impossible, but they can be made up).

it gets even better if you run Turbo S 5th and 6th with the Turbo S R&P;

Turbo S R&P w/ Turbo S 5th and 6th;

1st; 3.182 :1
2nd; 2.000 :1
3rd; 1.435 :1
4th; 1.111 :1
5th; 0.882 :1 (not easily sourced)
6th. 0.711 :1 (not easily sourced)
final ratio 3.446


if you wish to run these combinations for the smaller, more common 25.0" tire size... doing the math, my Dunlops make 818 revs per mile at 36 psi.... michelin Pilot Sport 2, 295-30-18s are 25.0" and make 832 revs per mile... Pirelli P-zero Corsa or Rosso 295-30-18 is also listed at 832 revs per mile... if you run the 25.0" Pilot Sport 2, or P-zero Rossa, just multiply all the speeds listed above by 0.9832 (832/818)

my transmission project, now completed with the taller 5th and 6th is as follows:

transmission with 48 k miles; $1,800
purchase 5th and 6th gearsets; $1,730
labor to install/(4 hours)/misc parts/(local Getrag specialist); $620

total; $4,150 ... yes, i think i got off easy, and i've got a good spare transmission in the car).

hope this helps.

regards,

Odurandina.

Have you guys ever seen is link? I've always found it to be very helpful
http://members.rennlist.com/951_racerx/

actually - I think there's so issues with navigating that site. Here's a more direct link that shows most 944/951/968 gear ratios:
http://members.rennlist.com/951_racerx/gearing.html

968 6 speed transmission update:

got my LSD recently almost brand new from a trusted Rennlister for just under $1 K....

there was no way i could see installing the lsd without picking up all 4 up gears from Scott.

cost for the 4 gears was $3,000.

i ended up getting what i needed, killing two birds on the lsd install....


stock 968 ratios;

1st; 3.182 :1
2nd; 2.000 :1
3rd; 1.435 :1
4th; 1.111 :1
5th; 0.912 :1
6th. 0.778 :1
final ratio 3.778 w/ open diff.


and w/ the new gears (in boldface) for the V8;

1st; 3.182 :1
2nd; 2.000 :1
3rd; 1.230 :1
4th; 0.930: 1
5th; 0.729 :1
6th. 0.600 :1
final ratio 3.778 w/ limited slip diff.



numbers; flat out, spirited and economy driving running the 25.6" tire. notice the

short ratio 1st and 2nd gears, but smooth transitions from 2nd to 6th running the new gears.

the last number is the increase in speed at 3000 rpm after shifting to the higher gear


ratio ... speed @ 6000 rpm ... speed @ 4500 rpm ... speed @ 3000 rpm ... up (mph) @ 3000 rpm

.600 ......... 194.4 ..................... 146.0 ..................... 97.2 .......................... 17.2

.729 ......... 160.0 ..................... 120.0 ..................... 80.0 .......................... 17.3

.930 ......... 125.4 ...................... 94.1 ...................... 62.7 .......................... 15.3

1.230 ........ 94.8 ....................... 71.1 ...................... 47.4 .......................... 18.3

2.000 ........ 58.3 ....................... 43.7 ...................... 29.1 .......................... 10.8

3.182 ........ 36.7 ....................... 27.5 ...................... 18.3 .................................



and the oem transmission w/ very short gear shift points;


ratio ... speed @ 6000 rpm ... speed @ 4500 rpm ... speed @ 3000 rpm ... up (mph) @ 3000 rpm

0.778 ........ 149.9 ..................... 112.4 ..................... 74.9 ......................... 11.0

0.912 ........ 127.9 ...................... 95.9 ...................... 63.9 .......................... 7.8

1.111 ........ 112.2 ...................... 84.1 ...................... 56.1 ......................... 15.5

1.435 ......... 81.3 ....................... 61.0 ...................... 40.6 ......................... 14.0

2.000 ......... 58.3 ....................... 43.7 ...................... 29.1 ......................... 10.8

3.182 ......... 36.7 ....................... 27.5 ...................... 18.3 .........................



how i found these two (3rd and 4th) gears;

i recently had sourced taller 5th and 6th gears for my spare 968 box, and i was readying to have the LSD installed.... but just before going ahead, i thought i'd give Scott Dewitt (Advanced Automotion) a call and make 100% sure that nothing can be done about the sizable gap i had between 4th and 5th on my LSx swap transmission... but of course, he solved it... recently finding .880 and .930 Audi gears to run in the 4th gear slot.... either gear eliminates the problem of the not-friendly short 1.111 4th gear.


so,

which gear to select ?

the .880 4th gear would make 133 mph at 6,000 rpm (25.6 inch tire).... but on the secondary roads (and lower highway speeds) the rpms would be running a bit lower than ideal if attempting to launch; thus making the .920 gear the better option; the .920 will make about 122 mph at 6,000 rpm with the car near peak torque once switching to 5th..... the .729 5th will make 160 mph at 6,000 and the .600 6th gear will make 195 mph/6,000 rpm....


but, the fun didn't stop there;

Scott has a 1.23 3rd gear to eliminate the stock 1.45.... so you're left with just having to deal with shorter 1st and 2nd gears. but, it's easy to see from the table that the rest of the way, the transmission is able to take full advantage of the torque and hp of the LS V8.




D.D..: "For a small price, I can install this little blue button to get you down...."

www.youtube.com/watch?v=6MMkiq8Kxis