sunnyr

Knowing next to nothing about the transmission construction/internals, I am curious if the ratios from the 997.2 Carrera/S transmission would work on the GT4 transmission?

The ratios and max speeds (when paired with the stock GT4 final drive) -

usctrojanGT3

Question for all you experts....I'm going to running 19 inch wheels with the same tire dimensions so I'll have a 1 inch smaller total tire/wheel diameter...how will this affect the gearing?

s2ktaxi

your speedo will be off by 5%

jphughan

You'll be going a bit slower than your speedo indicates, so it would be equivalent to a slightly taller final drive because your top speed in a given gear will be lower. On the other hand, acceleration and braking might improve depending on the wheel selection since you will likely have less rotating mass, assuming tires with similar longitudinal grip capabilities.

usctrojanGT3

Wheels are 19x9 and 19x11 BBS E88s with Trofeo Rs (same widths and ratios as OEM but just in 19 vs 20 sizes).

RealityGT

Your going to be significantly lower.. The general rule of thumb is to stay within 3% of total wheel diameter so the ecu doesn't freak-out. -Unsure about the GT4 ecu..

Phokaioglaukos

I thought the 3% was the difference between front and rear wheels/tires, not between OEM and installed wheels/tires.

Ochocoronas

^^^^^ Front to rear is correct.

GTgears

997 is an Aisin gearbox. caymans are Getrag. No swapping parts.

RealityGT

changing the OEM tire dia by more than +/- 3% can throw off your ecu's speedo calibrations. Most concerning is that it can mess with a vehicles ABS systems, with potential for accident.

BGB Motorsports

Every tire manufacturer lists the circumference for their rubber or the "rollout." Your car comes with 245/35/20 up front and 295/30/20 in the rear which is a set of 84.04" tires up front and 84.72" in the rear. If you don't want a difference in ABS behavior OR speedometer readings, just find yourself another set of 84" rubber OR keep them consistent which will keep the brakes happy BUT if you go shorter equally, your speedo will be different.

Phokaioglaukos

Any change from OEM tire circumference will affect the speedometer readings.

Changing front and back tire circumferences evenly (or within about 3% difference from OEM front to back) will not inhibit ABS or other traction or stability control features, as I understand it.

Accel Junky

It sounds like we are basically screwed on this one. Nobody wants make the shorter 2nd gear and nobody wants to make an aftermarket ring and pinion. I wonder if we could organize a group buy with upfront payment of that would motivate someone to meet this need?

Mike J

It will take time - these cars are brand new and fully warrantied - I bet less than half are even broken in. The demand will pick up in three-five years time, unless people just get used to the gearing, or move onto the next new thing. That might leave those who buy the used cars at a discount itching to change the gears ....

Accel Junky

Unfortunately you are probably correct...which sucks because I really think the gearing is a major barrier to myself and some others enjoying this car on the street. Track, probably a different story I'm willing to admit that and will hopefully be out to see this upcoming season.