The Porsche 915/68 5-Speed Transaxle (911 Carrera 3.2 1984–1986, USA/CDN/J) is a five-speed manual transaxle.
First gear is 3.182:1 and 5th is 0.789:1. Divide one by the other and the overall spread is 4.03:1. That is a middling spread for a five-speed: enough first gear to leave a junction without drama, and a top gear that is not only for motorways.
5th is an overdrive at 0.789:1: the output shaft turns faster than the input shaft. 4th is direct drive at 1.00:1.
The biggest step is 1st to 2nd, where the ratio drops 44%. The smallest is 3rd to 4th at 21%. A drop that size lands the engine well down the rev range after the change, so it pays to know where the torque lives.
It is a transaxle, so the final drive sits in the same case: 3.875:1 as listed here. The speed table uses that figure and nothing else. With a 3.875 final drive and 225/45R17 tyres, 5th at 6,000 rpm works out at 235 km/h (146 mph), and first runs out at 58 km/h (36 mph). At 70 mph in 5th the engine turns about 2,880 rpm.
Nearly the same box as the Porsche 915/62 5-Speed Transaxle (911 SC 1980–1983): 2nd is 1.778 here and 1.833 there; 5th is 0.789 here and 0.786 there. That page is the one listed for search; this one stays for anyone after this exact version.
Ratios
| Gear | Ratio | Step |
|---|---|---|
| 1st | 3.182:1 | - |
| 2nd | 1.778:1 | 44.1% |
| 3rd | 1.261:1 | 29.1% |
| 4th | 1.00:1 | 20.7% |
| 5th | 0.789:1 | 21.1% |
| Final drive | 3.875:1 |