DFASTEST951

Most of you know I blew second gear. So, in my research, a highly competent shop suggested I go with the six speed 968 tranny. I already know about reconfiguring the speedo. Not a big deal. I also have to harden the gears as well. I was told the 968 has a slightly taller first gear and an overall taller sixth. What do you guys think? Are they weaker than a 951 tranny? Stronger? Better?

AL951

Do it Joe, you will never look back my friend!

look at it this way, with a 6-speed gearbox, depending on your final drive, you may have the same top speed, but you will get there faster.

Regards,
AL

maximus951

The 968 unit has a stronger case and hardened (shot peened) gears. Also, you will want to find one with the Torsen torque bias diff (very effective LSD) - I think they became the standard option in 93 or 94. Lastly, you will need the 968 torque tube along with the shift rod - the tube is shorter to compensate for the slightly longer transmission. Someone here posted a FAQ on getting the speedo pickup to work off of ABS since the 968 doesn't supply signal from the tranny.
Are you still in Vegas?

DFASTEST951

Thanks Al, Maximus951, that's great info. Are you sure the gears are hardened? Anyone else confirm this?

I already have an 89 Turbo S LSD so I believe I'm set there. Yup, still in Vegas...

JET951

you dont need the torque tube or the shift rod. the box will go straight in. you can get them with the torque biasing or a clutch type. the clutch type is much better, although it is only 40% locking(so is the torque biasing one). the clutch type work on both power and over run. making the car much more stable. i would buy an after market 80% clutch type LSD for the 968 box.

JET951

also get your self a 968 abs unit and the blue abs relay and wire it in to your speedo, very easy to do. and your 944 turbo LSD wont fit in the 968 box. the 968 box uses a much larger unit from a G50 box

Robby

ok, not sure about this- the 968 6-sp is a great way to go, but- are you going to be using the 3.38FD of the 951 or the 3.78 of the 968? I'm assuming you'll be using the 968's, as other's, like Kurt Erickson's JME monster did... IF this is the case, then you will have a LOWER TOP SPEED potential!!! You can check out Racer X (Danno's) site to check his gear charts if you'd like to confirm, or one of a dozen other ways- this is easy info to find, but I'll give you the #'s below from a 1992 C&D that tested the 968- btw- yes, if you have a choice, get a Torsen, like has been stated- Some prefer ZF (which was optional on 968 only in 1992) for street, but most seem to prefer the Torsen & the Torsen is more durable & does not need rebuilding (supposedly) etc...

Anyway, the following is a list of the 968's gears & it's mph at redline in said gear. These are w/stock RD tires, from C&D- my math matches all but 6th....

The 968 had a 3.78FD & 6500(?) redline...
1st - 3.18 - 40mph
2nd - 2.00 - 63mph
3rd - 1.44 - 88mph
4th - 1.11 - 114mph
5th - 0.91 - 139mph
6th - 0.78 - 153mph - I get 163 by my math, but other's here have comfirmed short of 160 by GPS...? I think they listed a factory quoted top speed, possibly...

The 951 had a 3.375 FD & 6400 redline
1st - 3.50 - 40mph
2nd - 2.06 - 67mph
3rd - 1.40 - 99mph
4th - 1.03 - 134mph
5th - 0.83 - 167mph

The hot ticket would be a 968 w/custom FD or w/individual custom gears- stick w/1st, as-is, then go to custom 2-6, or at least 3-6. Still, the custom FD would be much cheaper- I think some people are working on this right now...

Going to an extremely tall RD tire effectively makes your gearing taller & thereby gives you higher potential at redline. ? Unfortunately, it doesn't help enough in a case like this- you'll never get much w/out going ridiculously crazy. I've always wanted a 285/35/18 on my car- that's huge! Even that tall, though, a 951 would redline (@ 6400) the stock 5th just a hair below 175...

EDIT- yes, Jet's argument for the ZF is a decent one- they do stabilize under braking, particularly, but then many lap times reflect the Torsen to be better... it really depends on what type of driving you do, etc... The ZF on 80% lock sounds very excessive to me, however. I would put 60% at about the max, but then I haven't ridden in anything that even breaks 40%- the ZF's lose lock over time, so I'd doubt many of the 951's have more than half of the 40% they came with... The closer you get to 100%, the closer you are to full on locked diff & would be impossible to drive in corners... Drag-racers lock diff's as the cheap way to go down the 1320...

JET951

we use a custom made 80%lsd made in Australia. it is the only way for our cars on the track. 40% gives way too much slip, inside wheel spinning. and you are correct Robby it does depend on the particular driving style. for us its the 80%
for example. we just won the NSW porsche club PR technology championship with a 951 with this particular LSD. 80%in a 951 is not exsessive. 80% in a 911 is exsessive though. here is a pic of it. its the LSD on the right

special tool

Yeah - you don't need to harden anything. Don't get taken to the cleaners again, Joe. This is not a Honda tranny.

However, you and the top speed thing, a 951 R&P in that 968 box with your torque and the close ratios will put you over 200 (7000 RPM) and still a nice box.

JET951

so the 951 pinion fits in the 968 box? being that the diff is bigger in the 968, the 951 crownwheel may not fit over it. and where does the extra gear go on the 951 pinion?

special tool

Yes - friend of mine has a 968 with an S2 R&P - but that is crazy and so is he.

JET951

i gotta check up on this one

special tool

Maybe the owner of this tranny will chime in when he is done stuffing his face with doughnuts.

Porschefile

In the US, who the F really drives 200mph?! Seriously, lets be realistic here. Top speed is not that important. If you lived in Germany it would make more sense. Here, ~150mph is more than enough to have fun and put you in jail, plus you'd get the added benefit of acceleration as opposed to a FD capable of 2 million mph.

Is the 968 R&P really all that strong? If it is basically a G50 R&P, those can handle more than enough power. It's been awhile since I researched any 968 stuff but, I seem to remember hearing about R&P failures or some other kind of reliability issues with the transaxles even under stock 968 power? Does anyone know anything about this, or is my mind just playing tricks on me?

333pg333

It would seem that the box is entirely dependent on the users intentions. Having a car that does 200mph is cool but not much use to most of us. I am going to get the same diff and S2 w/p as Jet. Should make up for my now non working stock 40%. His car rockets out of corners and is balanced at the track.