[Shad Laws]

Hello-

So, Why have a 1st gear that redlines at 30mph when you have an engine that can take off in 2nd gear without a fuss?

Selecting good gearing depends on a lot of things. First, the intended application... let's assume a high-powered street car for now. Second, the tire size. Let's assume ~24.25"-24.75", which is around the size most GL cars have. And, it depends on the rev-range of the engine. Let's assume a normal-ish 3k-6k powerband or so.

The first thing to do is select your lowest and highest gear. The tallest 1st gear I would use would be about ~12:1 overall ratio. This is accomplished on Porsche boxes with 3.875 x 3.18 (late 915) or 3.444 x 3.50 (G50, etc.). But, even this tall of a gear _does_ compromise some acceleration. In fact, most autocrossers prefer ~14:1. This is accomplished with 3.875 x 3.80 (VW), 4.429 x 3.18 (901, early 915), etc.

The highest gear is a bit trickier. If you still want your tallest gear to accelerate well at highway-ish speeds, then you really don't want anything more than ~3.1:1-3.2:1. This is accomplished with 3.875 x 0.82 (VW, late 915), 4.429 x 0.71 or 0.72 (901, early 915), etc. This puts the car at 3000rpm at highway speeds (~70mph or so). Realistically, anything taller is going to really decrease the acceleration of the car, but it may help gas mileage. There's really no reason to go higher unless you want gas mileage...

Now, with your tallest and lowest gears given, you can fill in the blanks for the middle gears. And then you discover something: the stock 1st and 2nd that VW or Porsche gave you are just about perfect. If you make them any tighter, you'll have to make the upper gears farther apart and acceleration suffers badly. If you make them any further apart, your upshift into 2nd will place you way outside the powerband. And, changing these ratios is very expensive. So, they are very infrequently changed :-).

For a 4-speed VW box intended for a moderately powerful and torquey GL-type of vehicle, I'd use the following gears:
3.875 x 3.78 = 14.7:1
3.875 x 2.06 = 7.98:1
3.875 x 1.26 = 4.88:1
3.875 x 0.82 = 3.18:1

Or, if you have a lot of torque and don't mind the slight low-speed loss in acceleration (and increase in price from aftermarket R&P), then you can do this:
3.444 x 3.78 = 13.0:1
3.444 x 2.06 = 7.09:1
3.444 x 1.32 = 4.55:1
3.444 x 0.93 = 3.20:1

Both of these combos are relatively cheap to gear up, compared to custom everything. Just MHO... all of the above is subjective and holds no absolute truths for anyone :-).

Take care,