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Storm Transmission Modifications

With the Open differential, the storm constantly would lose traction launching or in turns, and torque steer was at the verge of being dangerous. Most of my launches at the track were one-wheel burnouts, and just accelerating on the highway turned into a battle to stay somewhat straight as the oscillation of power from wheel to wheel would pull the steering wheel left and right. A group of us decided that we needed to get a group buy going and contactd Quaife in the UK and have a custom ATB LSD made for our transmissions. The group consisted of 32 individuals around the globe, including the UK, Netherlands, Singapore, and the US. These people all shared one thing in common, an Isuzu built tranny. The vehicles included the Geo Storm, Isuzu Impulse/Stylus, Lotus Elan M100, and the Chevy Cavalier. The Quaife LSD retailed for $1600US + shipping, but when you have a group buying a bunch of them all at once, it dramatically lowers the price! I ended up paying $750 + $33 shipping, not bad considering what the Quaife LSD does.
Quaife Limited slip differential
Installed into the Storm GSi transmission
Quaife LSD installation
Once installed into the Storm, there is an immediate difference noticed in launching and torque steer, and an even greater difference noticed while making turns, specifically high speed/power turns. With an open differential, turning would usually make the car respond by pushing you out of the turn. With the Quaife though, you actually feel the car being pulled into the turn, with no wheel slip. It is quite an amazing feeling, and well worth the $750 I spent on it.

Here is the Quaife marketing blurb on the Automatic Torque Biasing LSD:
Quaife LSD cutaway
The QUAIFE Differential powers both drive wheels under nearly all conditions, instead of just one.
With an ordinary open differential, standard on most cars, a lot of precious power is wasted during wheel spin under acceleration. This happens because the open differential shifts power to the wheel with less grip, along the path of least resistance.
The QUAIFE, however, does just the opposite. It senses which wheel has better grip, and biases the power to that wheel. It does this smoothly and constantly, and without ever completely removing power from the other wheel.
In cornering, while accelerating out of a turn, the QUAIFE biases greater power to the outside wheel, reducing inside-wheel spin. This allows the driver to begin accelerating earlier, exiting the corner at a higher speed.
The QUAIFE also controls loss of traction when the drive wheels are on slippery surfaces such as ice and snow or mud, providing the appropriate biased traction needed to overcome these adverse conditions. The QUAIFE Differential provides constant and infinitely variable drive.
Power is transferred automatically without the use of normal friction pads or plates seen in other limited-slip designs.
The QUAIFE'S unique design offers maximum traction, improves handling and steering, and puts the power where it is needed most. A definite advantage whether on the track or on the street.
The QUAIFE is extremely strong and durable and since the Quaife is gear operated, it has no plates or clutches that can wear out and need costly replacement.
The QUAIFE is great for street driving or racing. Racers don't have to put up with locking mechanisms or spools that tear the steering wheel out of their hands when cornering. Because it behaves like an open differential during ordinary driving, street drivers will have trouble telling it's there until pushing the cars limits.
The QUAIFE has been proven in everything from SCCA Rally to Formula 1. It provides autocrossers with such an advantage, it has become "required" equipment for a winning effort.

Geo Storm/Isuzu Impulse/Stylus/I-Mark Transmission Specifications

Transmission 1st Gear 2nd Gear 3rd Gear 4th Gear 5th Gear Reverse Final Drive
Base Geo Storm SOHC 2+2 3.727:1 2.043:1 1.448:1 1.027:1 0.829:1 3.583 3.833:1
Stylus S SOHC 3.727:1 2.043:1 1.448:1 1.027:1 0.829:1 3.583 3.578:1
Geo Storm GSi / Isuzu Impulse XS / RS 3.909:1 2.150:1 1.448:1 1.027:1 0.829:1 3.583 4.117:1
1992 XS (maybe 92 GSI too) 3.727:1 2.150:1 1.448:1 1.027:1 0.829:1 3.583 4.117:1
Lotus Elan M100 3.333:1 1.916:1 1.333:1 1.027:1 0.829:1 3.583 3.833:1
Geo Storm GSi / Impulse XS - 4speed AUTO transmission 3.027:1 1.619:1 1.000:1 (OD) .694:1 n/a 2.272:1 4.015:1

I-Mark "S" or Sunsport 1.5 Carby 3.727:1 2.043:1 1.333:1 0.923:1 0.744:1 3.583:1 3.578:1
I-Mark XS 1.5 F/I 3.727:1 2.043:1 1.448:1 1.027:1 0.829:1 3.583:1 3.578:1
I-Mark LS 1.5 Turbo 3.500:1 1.916:1 1.333:1 0.923:1 0.744:1 3.583:1 3.833:1
I-Mark RS 1.6 DOHC N/A 3.727:1 2.043:1 1.448:1 1.027:1 0.829:1 3.583:1 4.117:1

Automatic Transmission Ratios
89-91 Base 90-91 GSi 92-93 Base 92-93 GSi
First 2.841 3.027 2.841 3.027
Second 1.541 1.619 1.541 1.619
Third 1.000 1.000 1.000 1.000
Fourth - 0.694 - 0.694
Final Drive 3.526 4.015 3.526 4.015
Part #s amd price list for replacement syncros and forks for the transmissions:

1st - 2nd syncro = 94335056 $111.79
1st - 2nd fork = 97015681 $ 34.66

3rd - 4th syncro = 97109769 $127.31
3rd - 4th fork = 94464752 $ 28.94

5th syncro = 97109770 $160.68
5th fork = 94109002 $ 28.46 lists two part numbers for the 3-4 and 5th gear synchros, they're the same ones listed for the Fiero.
I ran a pretty cool simulation with t