odurandina

for racing a 968 with a turbo set up, the short ratio 968 box (very rare transmission option) would be best. if you're racing an LS motor on the track, a stock 968 box would be fine. but, Joe's not racing on the track, so "his flying mile" box with the same R&P as the Turbo S box, but stock 5th and 6th is going to be very close to the best. he'll be able to find about 8~10 tire combos between about 24.7" and 25.7" to get him to from about 195~205 mph at the redline i don't think any turbo 4 could ever get a car past about 180 mph in only a mile. but what do i really know... if you're running a 3.0 turbo with 375+ hp at the flywheel for the street, Raj's box (with the long R&P, but also the slightly longer 5th and 6th gears), which tops out at about 185 mph is very close to perfect... Porsche knew what they were doing... again, you have a lot of leeway with tires. if you want great highway cruising, you might want to run a 25 1/2" tire, etc....

if you have an monster LS engine, for the street, the only 968 box that i would be happy with, would have the tall 0.600 6th gear. and have me with my tire set up at about 98 mph at about 3,000 rpm... the only problem with is that it would create a chasm between the stock 5th and .600 6th---- so i'd rather have that chasm occur between 4th and 5th.... so install the longer 5th gear too, because i want to be able to putt around at 2,000~3,000 rpm cruising about town or being stuck in rush traffic and be able to use 4th and 5th to give me a very wide range of speeds without beating the crap out of my engine.


if i had unlimited funds, for my future LS car for the street, i'd choose the 3.46 Turbo R&P, a 5th gear about .860 and .680 6th. i'd be able to keep the car fairly close to peak power all the way to 200 mph.




yes, but there's not 19 time zones between L.A. and East Oz by way of the Pacific Ocean.... there's only 5. L.A. is 19 hours behind sydney by way of going back in the other direction. but i still thought Oz was like more to the opposite side of the world from America.



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George D

Here is a post I did on another list. I'm considering just the sixth gear. Quote:

There is a write-up on one of the V8 hybrid sites using the g50 box with success. Quote: The reason I inject this idea among our fair board members is because of the setup of a very fast car know as the Ultima GTR. It utilizes a chevy small block V8 350 coupled with the G50. As many of you already know, this little dandy has set the world record for 0-100-0 mph record. Though it may be ridiculously lighter in weight, I also have learned that the G50 can withstand very large amounts of horsepower without buckling under pressure. Link for you: http://www.porschehybrids.com/php/vi...php?f=2&t=1033

When my 951 five speed wore out. I replaced it with a G50 968. You can get gears from JH Motorsport. They can get whatever gears you want, but I'm only considering the 6th gear .60 for sixth. http://www.jhmotorsports.com/shop/ca...peed-p-45.html

With my car on the lift, at idle you can hear some trans noise. We think it's just backlash and we have semi solid mounts, so any noise is amplified. We will try a heavier weight gear oil to see if this dampens the noise. If not, we are opening up the trans and fixing whatever is worn. If we do this, I will be installing the .60 sixth gear.

The six speed is a very good fit for our cars. You shift in the sweet spot around 4 to 4500K when WOT. Chris Cervelli was the number one unlimited driver in a 951 3.0 six speed in SCCA here in AZ about 8 years ago using this trans with few issues.

I have locking bolts on my axles, and the LR units look really nice. Olli's post makes sense, but I don't have the time to make stuff not designed for our cars work without shelling out too much labor $ for R&D.

JH Motorsports has the sixth .60 gear in stock for about $700 bucks. Not cheap, but it's what I'll do if I have to open the trans anyway.

Defastest, keep us posted about the R&P setup. If it was cheap enough, I might bite.

George

George D

http://www.jhmotorsports.com/shop/ca...peed-p-45.html

This link should work. Check out the chart showing speed in 6th with the 968. If you can hit 7K you are approaching 200mph with the stock unit. If your tires are larger than stock, you will be even faster. (Allow 2 to 3 weeks for delivery on the gears, depending on current availability.) Click HERE for our 6th gear RPM vs. MPH chart

blitz951

George D, can you tell us what your mph is at max rpm in 1-6 gears.
Looking at the 5 speed compared to the 6 speed it seems we can get a higher mph per gear with the 5 speed. For example, in first gear with the 5 speed we get 42 mph which is more than the 6 speed.

odurandina

there's a huge 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 9000 275-35-18s. running the 35 aspect ratio not only gives me a little more top end, but the ride is a lot less harsh. that's why i went with this tire size.


bear in mind that whatever tire combination you run with a stock 968 transmission, your top speed in 4th gear will be 82.3 % of your top speed in 5th gear.... top speed in 5th gear will be exactly 85.3 % 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 (theoretical) running 25.6" tires and the stock box is 162.1 mph @ 6,500 rpm.


fitting taller gears; some numbers....

starting with the 5th gear, changing to from .912 to an available .729 01e gear will make 172.9 mph at 6,500 rpm and make 160.0 mph for the LS engine at 6,000 rpm....

running the 25.6" tires with a 0.680 6th gear would give 185.3 mph @ 6,500 rpm

running such a large tire with a 0.600 6th gear would give 210.0 mph @ 6,500 rpm

obviously, this gear doesn;'t look very attractive for a turbo, running such a large tire, but you have the option of going to a smaller tire, (a Pirelli P-zero Corsa 295-30-18 is only 25.0")... for a BIG LS engine, staying with the large tire, actually looks pretty good, (and makes low rpm for normal highway driving).... it's already been proven that adding headers will make 23~28 hp for any LS3.... so, this puts us right at about 500 hp at the flywheel running an ls3 with the GM hotcam and headers... and you'll do even better by adding a few goodies in the valvetrain... add ported heads and Fast intake and you'll be making 550 + hp....

http://www.jegs.com/p/GM-Performance...27485/10002/-1

such a car should be able to reach 190 mph because you'd be at near peak hp at that speed.

190 mph @ 5880 rpm
195 mph @ 6035 (would require head work)
200 mph @ 6189 (head work + NO2)


now for the Turbo S diff.... ok one moment please..... 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...

top speed in 5th gear = 151.2 mph at 6,500 rpm

top speed in 6th gear = 177.3 mph at 6,500 rpm


be back in a minute with the numbers if you could add the Turbo S 5th and 6th gears (likely to be extremely scarce).



now i'll run the combinations for the smaller, more common 25.0" tire size.


my Dunlops new 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, P-zero or Rossa, just multiply all the speeds listed above by 0.9832 (832/818)


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George D

I don't know, never checked. The stock five speed will have a higher top speed with tires being the same.

George D

Here is an estimate based on stock tire sizes.

blitz951

Thanks George,
Not to get of the subject but are you using a Precision turbo and if so what do you think of it?

DFASTEST951

I'm sending Scott both my five and six speed so he can see for himself what's interchangeable and available. Still, the $2400 for the ring and pinion is over $1,000 cheaper than anywhere else. who's in? We need an order of ten.

George D

Joe,

Is this for the six speed?

DFASTEST951

Hi George, yes, it's for the six speed. You and I have almost twice the hp as the factory turbo 968 and they used a 3.4 ring and pinion. I'm going in for upgrades as well so this is a must. I'd even go to a 3.1 or so if the GTM and the Ultima guys jump for that. The factory ring and pinion is just way too short. Are you in? Anyone else? Give Scott a call and place an order. Let's do this!

Thom

This is the mod I ultimately wish to do on my car and at $1800 I would have been in, but at $2400 plus the fact that I have other mods going on that have a much higher degree of priority, this a no go for me now.

nick_968

Pretty much in the same camp as you Thom, would love to do this but by the time it hits the EU with an extra 25% of tax and import duty plus fitting its too expensive right now.

333pg333

I'd like to see a chart with the adjustment for this r&p. See what the rpm drop would be etc...

George D

Me too.