Finally know what's inside my transaxle
04-23-2002, 05:53 AM
#1
Race Car
Thread Starter
Finally know what's inside my transaxle
I finally got the gear ratios for my transaxle, which is a mag cased box from a 77 with billet bearing reinforcements, internal spray bar and external cooler, internal Wevo gateshift, external Robotek spring-loader, custom GT gears, and GT limited slip at 80%.
It's got a taller-than stock second, and close-ratio jumps up to a very low fifth.
1st 11:35 (3.182) Stock
2nd 20:32 (1.600) 3 steps taller -- stock is 1.833
3rd 23:29 (1.261) Stock
4th 25:27 (1.080) 2 steps shorter -- stock is 1.00
5th 26:25 (0.962) 4 steps shorter -- stock is 0.821
With my current rear tires, my gearing should work out like this:
47 to 135 mph is all above 4000 rpm, with very short throws. It's ideal for the track, since none of the gearing is wasted.
With the tires I'm planning on running during the <a href="http://www.opentrackchallenge.com" target="_blank">OTC</a>, the <a href="http://www.pelicanparts.com/ultimate/image_uploads/0JacksGearing2.jpg" target="_blank">top speed goes up to 141</a>.
It's got a taller-than stock second, and close-ratio jumps up to a very low fifth.
1st 11:35 (3.182) Stock
2nd 20:32 (1.600) 3 steps taller -- stock is 1.833
3rd 23:29 (1.261) Stock
4th 25:27 (1.080) 2 steps shorter -- stock is 1.00
5th 26:25 (0.962) 4 steps shorter -- stock is 0.821
With my current rear tires, my gearing should work out like this:
47 to 135 mph is all above 4000 rpm, with very short throws. It's ideal for the track, since none of the gearing is wasted.
With the tires I'm planning on running during the <a href="http://www.opentrackchallenge.com" target="_blank">OTC</a>, the <a href="http://www.pelicanparts.com/ultimate/image_uploads/0JacksGearing2.jpg" target="_blank">top speed goes up to 141</a>.
04-23-2002, 01:08 PM
#3
Racer
Join Date: Jul 2001
Location: Torrance ,Ca
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Jack,
Sounds great ! Just last week I dropped the motor and trans to install my new close ratio Powerhause II gears. I too retained the stock 3rd gear with taller 1st and 2nd, shorter 4th and 5th. Top speed at 7000 rpm for my car will be 147. While I had the gearbox apart I added squirters over all 5 gears circulated by a Tilton pump. I decided on a taller 1st gear for Cup Racing in order to make use of 1st during the rolling start. I'll have it up and running tonight and will be testing this weekend at WSIR.
You missed the carnage at the Streets recently, burning 914 and a 993 taking out the corner worker stand on turn 3.
See you at the track !
Sounds great ! Just last week I dropped the motor and trans to install my new close ratio Powerhause II gears. I too retained the stock 3rd gear with taller 1st and 2nd, shorter 4th and 5th. Top speed at 7000 rpm for my car will be 147. While I had the gearbox apart I added squirters over all 5 gears circulated by a Tilton pump. I decided on a taller 1st gear for Cup Racing in order to make use of 1st during the rolling start. I'll have it up and running tonight and will be testing this weekend at WSIR.
You missed the carnage at the Streets recently, burning 914 and a 993 taking out the corner worker stand on turn 3.
See you at the track !
04-23-2002, 01:43 PM
#4
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Join Date: Jun 2001
Location: San Leandro, CA
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Does anyone know if the ratios marked as "stock" on Jack's chart are stock for all 915 transmissions? If not, where would I go to find the ratios for a U.S. '84 Carrera?
Thanks,
Thanks,
04-23-2002, 05:07 PM
#5
Instructor
Instant G has a pretty cool spreadsheet that also might help (it lists stock ratios). I have no idea if it is correct!
<a href="http://www.instant-g.com/GearChart915.xls" target="_blank">http://www.instant-g.com/GearChart915.xls</a>
Just out of (morbid) curiosity, what do new gearsets cost?
Cam
<a href="http://www.instant-g.com/GearChart915.xls" target="_blank">http://www.instant-g.com/GearChart915.xls</a>
Just out of (morbid) curiosity, what do new gearsets cost?
Cam
04-23-2002, 05:45 PM
#6
The best place to check for stock gear ratios is in the back of the owner's manual that came with the car. After that I would check in Bruce Anderson's book, Porsche 911 Performance Handbook, and Paul Frere's book, Porsche 911 Story. All three are excellent sources of info.
04-24-2002, 02:52 AM
#7
Race Car
Thread Starter
In this picture, I'm close to redline at Thunderhill:
It's still a street/track compromise car, and probably always will be. Even the new race buckets are leather, and the AC is here to stay.
Right now, my co-driver and mechanic (Tyson at TRE in North Hollywood) is hard at work modifying the front upper strut mounts for a much more radical caster/camber setup. We've also moved the fuel pump to the front of the car, cut out a bunch of dead weight in the back, and re-established better mounting points for the rear swaybars. We're also adding a front splitter and 13-pound race seats and pulling all of the heavy stereo nonsense for the Open Track Challenge.
Piece by piece, we're going to build a very capable little 911.
It's still a street/track compromise car, and probably always will be. Even the new race buckets are leather, and the AC is here to stay.
Right now, my co-driver and mechanic (Tyson at TRE in North Hollywood) is hard at work modifying the front upper strut mounts for a much more radical caster/camber setup. We've also moved the fuel pump to the front of the car, cut out a bunch of dead weight in the back, and re-established better mounting points for the rear swaybars. We're also adding a front splitter and 13-pound race seats and pulling all of the heavy stereo nonsense for the Open Track Challenge.
Piece by piece, we're going to build a very capable little 911.
