Porsche Transaxle Gear Ratios

Colin CJ D · 11-28-02, 12:57 AM

Just starting all the offline research to gather the extra "bits" for the build.

Can anyone help by providing the gear ratio numbers for a 1984-1986 Porsche 911 transaxle? [img]images/icons/confused.gif[/img]

Thanks

Bill Bayard · 11-28-02, 04:33 AM

Colin,

1st..3.154..2nd..1.789..3rd..1.269..4th..0.96..5th..0.85.... final drive 3.44:1

FYI, at 6500RPM, with 25.5" tires, this translates to 1st..45MPH..2nd..80MPH..3rd..113MPH..4th..149..5th..169MPH

Bill

Gary Gibbs · 11-28-02, 10:22 AM

In my opinion what "we" need is a wide ratio 6 - speed. This will give us good accel in first gear. Not a lot of excess shifting due to the spread, and decent top speed (and thus highway cruise RPM). I would like to see overall ratios (gear and final drive) something like:
first 10.93
second 8.33
third 5.94
fourth 4.57
fifth 3.61
sixth 2.17

spread 1st - 6th 5.05

Bill Bayard · 11-28-02, 11:04 AM

The Porsche G50 6 speed from a 993 should do the task. The trick is finding one! They came standard with LSD. Most other 6 spd gearboxes are too long because of the length required for the sixth gear. The G50 6 spd is only 1 1/2"longer than the G50 5 speed which I have in my car. However, it requires a different(older style) rear cover for ease of mounting. The G50 6 speed would fit with very minor modification. I will post the 6 spd ratios soon, as I'm looking at putting one in my car.

Colin CJ D · 11-28-02, 06:19 PM

Thanks Bill.
I have a line on 1987 G50 5-speed with only 47k miles on it. Looks pretty good.

[img]images/icons/grin.gif[/img]

12-01-02, 09:18 PM

Powerhaus II will give you any ratios you want in the Porsche transaxle (within reason.) They have all sorts of goodies like billet shift forks (reportedly the weakest part of the G50) and beefed up, billet side plate and a nice LSD of their own design that is supposed to be the bomb for street/race use cars.

Bill are those the ratios for the G50 and not the G50/50 from the turbo 911 (sometimes called the 930)? If so, I feel better about the gearing that I have. I haven't been over 3rd gear (dune buggy mode around the subdivision), but 1st didn't feel as bad as some have indicated. I could start in 2nd, but wouldn't recommend it as the norm.

One can also purchase just 5th which only requires the end cap be removed. This will give you nearly 200mph in 5th, but a huge jump from 4th to 5th. I wouldn't recommend this either. The cheapest way to up the ratios is through a guy in Australia who makes gears for the G50. I know he makes the G50/50 ratios but beyond that I am not sure. As I recall the price worked out to be around 300/gear when you bought all 5 (1st is integral with the input shaft.)

Bill Bayard · 12-07-02, 07:24 AM

Upon further research, I have discovered that the 993 G50/20 6 speed gearbox has been prone to failure, when hooked to a high torque engine. Also, the 6 speed is longer than the 5 speed, and might be impossible to fit in a 40, due to the physical limitations of the distance between the rear bulkhead and the rear clip.
According to Chris Carroll of Powerhaus, the older style G50 5 speed, that I have in my car, can be modified to just about any configuration desired. While ring and pinion sets are limited, the gears sets available are quite extensive.