Comparing Porsche 997 and 991 Manual Transmissions
Let’s start with the fact that neither feels as good as the S2000 manual transmission. In fairness, I’ve yet to drive any manual transmission that felt as good as the S2000. Many say that you can ‘get close’ with the Numeric Racing shifter and cables. I’ve not experienced a 911 with this set-up, so I can’t confirm if the claim is just Internet lore or truth.
This post really isn’t about how it feels rowing the shifter or the precision of the linkage. It’s more about how gearing affects the drive when comparing the Porsche 997 and 991 manual transmissions.
I’ve described the 991 GTS as giving you more T and the 997 GTS as giving you more S. I think the differences in gearing help to explain this impression. The 991 is a better Grand Tourer for a number of reasons and the extra overdrive gear is one of them; true to form on long stretches of highway. Similarly, the sportiness of the 997, including its gearing, is evident in the right scenario.
I’m fortunate to live within an hour of some of the best driving roads in the country, and I enjoy them as often as possible. These outings typically include a run through the twists & turns of mountain roads. I prefer the 997’s 6 speed transmission on this type of spirited drive. I find it easier to manage the torque of the engine which gives the feeling of more precise control. I’ll rarely use the brakes since the speed of the car is so easy to manipulate with just the throttle. I think the gearing plays a major role in this part of the experience.
When driving the same mountain roads, the 991’s 7 speed transmission just never feels like it’s in the right gear; either the speed or the RPMs always seem too high. I brake more often and change between gears more frequently trying to find the right part of the powerband for the next climb.
As I’ve tried to learn more about how the gearing affects the drive, I noticed a difference between the lower gear ratios in the 997 and 991:
As you can see in the table, 2nd and 3rd gear are slightly shorter in the 997 (i.e. higher numbers). The science says that shorter gears improve acceleration and make the car more performance-oriented. As most of the mountain driving is in 2nd and 3rd gear, the difference in gear ratios would seem to explain why the 997 feels more suited for the role.
It’s not just the overdrive gear in the 991 that makes it a better Grand Tourer. Taller gears (i.e. lower numbers) are better for gas mileage which is an important consideration on longer trips.
Two other minor points worth mentioning in a comparison of the 997 and 991 are also transmission related. The 991 includes an Auto Rev-Match which blips the throttle during downshifts. Porsche should have included a button to disable it. In a dig against the 997, the shift into 1st gear is somewhat stubborn when the transmission is cold. Other owners have suggested trying Motul over Mobile, though the change didn’t seem to make a difference for me.