I gave my wife a cordless impact gun for Christmas a few years ago as a joke. I wonder what she'd think about a set of gears?😁

 

Might want to consider some other sort of jewelry. I don't think she will consider motorsports grade gear steel a precious metal.

 

If they are packed in an Hermes box you might have a chance....

 

Now that there is information about a few available (or soon to be available) gear modifications, I will continue the series of comparison charts.

GTgears' kit:
981 PDK in (..), GT4 stock in [..]
- 1st remains stock GT4: 3.31, (3.91)
- 2nd: 36/16 = 2.25, (2.29), [1.95]
- 3rd: 1.6, (1.65), [1.41]
- 4th: 1.33, (1.30), [1.13]
- 5th: 1.1, (1.08), [0.95]
- 6th: 0.92, (0.88), [0.84]
- final drive: same for all

The ratios in the kit are very close to the PDK ratios used in the earlier "981R" post. Power is reduced in the 70-80mph range (see plot), but improved everywhere else in the usual speed range. Particularly in 45-70mph out-of-tight-corners range, acceleration is 15% improved!

 

Holinger kit:
This is currently shown at the Dundon website.
981 PDK in (..), GT4 stock in [..]
- 1st remains stock GT4: 3.31, (3.91)
- 2nd remains stock GT4: 1.95, (2.29)
- 3rd: 35/22=1.59, (1.65), [1.41]
- 4th: 33/25=1.32, (1.30), [1.13]
- 5th: 30/27=1.11, (1.08), [0.95]
- 6th: 28/30=0.93, (0.88), [0.84]
- final drive: same for all

Two things jump out:
1. 2nd is same as stock, so no improvement in acceleration below 80mph! and only a marginal improvement in the 80-95mph range.
2. 3-6 gear ratios look suspiciously the same as in the GTgears kit. Are they the same gears?

The conclusion here is that the lower ratio for 2nd is mising in this kit.

 

It's been a dozen years since we fired Holinger for stabbing us in the back over the 997 sequential gearbox. It was at that point we brought the gear business 100% in house. Not surprised to see them trying to follow our lead on something we are doing.

Regards,

Matt Monson
Guard Transmission llc.

 

AutoQuest Motorsports' Final Drive
In this option, the gears stay the same, but the final drive ratio is increased from 981 (GT4) stock (35/9)=3.89 to 4.62 (+19%)
This will increase acceleration by 19% at a corresponding 19% speed decrease at any given rpm. To recover highway cruising rpm & top speed, they offer a longer 6th gear (so says the post elsewhere on this board).

This option has approximately the same behavior as the GTgears kit, except for:
1. Acceleration in 1st is +19%
2. At the top end of stock 1st, in the 40-50mph range, the stock 1st setup is substantially better. I think this will only matter in very few scenarios.

For completeness, I am NOT associated with either Autoquest Motorsports, Dundon Motorsports, Holinger America, Guard Transmission, or anyone else having an interest in the GT4/981 transmission market. This information is based on publicly available information and provided strictly for entertainment purposes. Just sayin'.

 

Great to see others sharing this kind of analysis. Similar discussion over in the GT4 Final Drive thread.

 

Hi Mech33 - saw your post there this evening. Looks like we were both working on this today ;-)
In my view, the GTgears setup is the winner. It brings out all this engine has to offer.
Hard not to jump and commit right away ..

 

Agreed I think the GTgears setup is a better solution for folks looking for more out of their GT4 gearing.

I wonder what happens to the rev match functionality in sport mode, though... I assume that is a pre-programmed ratio of wheel speed to motor speed in each gear, and that would be thrown off by gear ratio changes?

 

I believe Sharkwerks, GT Gears, has experienced no issues with rev matching on their modified transmissions.

 

Interesting. It must be using an angular speed sensor then inside the trans measuring the pressure plate / input shaft speed for matching.

 

Packing things up to ship off to Sharkwerks for testing. We won't release it until we have hammered it. You won't see a group buy from us trying to pull money together to get it made. You won't see us beta-testing on the general public. We will just make it when we are satisfied that it's done right.

 

^ Very interesting, and good on you.

Alas, I sold my GT4, but I will say this: The gear stack in my 991.2 7MT is everything I hoped for from a re-gear of the GT4. 1-5 are perfectly spaced and nicely usable on the street, and 7th makes long hauls a lot nicer. And yes, I could live without sixth...as I am rarely in it.

I still think the gears are the key to unlocking a lot of fun in the 981 GT4, followed by intake and exhaust—but I'd spend money on the gears first. Very curious to see if that theory is right...

 

Matt, as you are not changing the 1st gear ratio are you intending 1st gear will utilise the existing gearwheel - only one gearwheel is shown in the photo?