http://www.turbosupras.com/pages/en/...nical/R154.htm

Here's a comparison of gear ratios of the 5 speed R154 vs the W58. Pretty similar, but not identical.


R154

1- 3.251
2- 1.955
3- 1.310
4- 1.000
5- 0.753


W58

1- 3.285
2- 1.894
3- 1.275
4- 1.000
5- 0.783

Just thought I'd share some info

 

And here are the gear ratios for the V160 (Supra turbo getrag 6 speed):

http://www.turbosupras.com/pages/en/...nical/V160.htm

V160

1- 3.827
2- 2.360
3- 1.685
4- 1.312
5- 1.000
6- 0.793

 

Figured I would add a bit to this...

Here are the final gear ratios with the respective stock rear ends for the given transmissions: 3.73 for R154, 4.08 for W58, and 3.13 for V160. Perhaps the final gear ratios give better perspective to the given transmissions in action with a given rear end...

R154 (w/3.73 axle)
1 - 12.126:1
2 - 7.292:1
3 - 4.886:1
4 - 3.73:1
5 - 2.809:1

W58 (w/ 4.08 axle)
1 - 13.403:1
2 - 7.728:1
3 - 5.202:1
4 - 4.08:1
5 - 3.195:1

V160 (w/3.13 axle)
1 - 11.979:1
2 - 7.387:1
3 - 5.274:1
4 - 4.107:1
5 - 3.13:1
6 - 2.482:1

The higher the number, the shorter the gear (ie. hit the redline at a slower mph). The lower the number, the longer the gear (ie. hit the redline at a higher mph).

The higher number allows torque to be transferred more easily to the wheels, lessening engine load. The highest gearing possible to ensure traction in 1st gear is preferred for an n/a or supercharger set up. If you are willing to sacrifice traction in first gear for increased performance in every other gear, the higher ratioed rear end is best. Highway rpm increase at any given mph with an increase in gearing.

In a turbo application, the lowest gearing that does not hurt spool time should be used. The lower gearing will make the engine load greater when under full throttle and not in boost. An increase in engine load increases exhaust gas velocity and spins the turbocharger more quickly. Go too low, and the car is so "heavy" on the motor that performance will suffer. Go too high, and the motor will not be under as much load: the turbo will spool later and fewer rpms will be available in boost.

 

very interesting... so the 134 should have a better take off then the w58 but after 3rd the w58 should be accelerating faster?

 

so a r154 w/ stock 4.08 will be even shorter, at least on 2nd and 3rd gear? damn. will need to find 3.76 lsd.

 

This is a good thread. And there was a noticeable difference in spool when I went from a 4.08 to the 3.76 rear end.

 

Taller rear end gearing (ie. 3.76) will cause the engine to load harder when asked to accelerate. By using more mixture, there will be more exhaust gas flow, which is what ultimately spools the turbo.

This can be taken too far as acceleration can suffer to the point that the motor simply can not rev when out of boost. But, in general, a lower gearing is preferred for a turbo car to increase engine load and subsequently increase exhaust gas velocity.

For an n/a or supercharged application, the shortest gearing (ie. 4.xx) that will still maintain traction in first gear is preferred for the most all around performance. If you can not hammer the throttle in first and still hook up with sticky tires, you would benefit from lower gearing. If you can hook up effortlessly when hammering the throttle in first, shorter gearing would be to your benefit.

Domestic V8 guys fiddle with gearing all the time. A number of those guys will run 4.10, 4.27, or even higher gearing on five speed transmissions geared very conventionally, like the R154. When doing this, they are sacrificing any traction in first gear at the expense of significantly more torque being available in 2nd-5th...and this all at the expense of revving the motor super hard when highway cruising.

The supercharged GS400 guys have done some tinkering with gearing as well. Most have found that the stock GS400 3.27 rear end will hook up in first gear, whereas TT Auto 3.76 gearing will leave them roasting the tires if they hammer the throttle. For the best 0-60 times, the 3.27 gearing is preferred. For the best rolling acceleration, the 3.76 (or even higher) would be preferred.

Gearing -whether n/a, supercharged, or turbocharged- is a balancing act. You want to find a gearing that will aloow you to get the most from your car for your given goals. Establish those goals and learn the consequences of the altering the rear end ratio before spending (and perhaps wasting) your money.