I agree. I'd love to read first-hand experience on a G before committing... ...but I don't think it's going to come. I might suck it up and be the first.

I know that, if it's a good mod, some others will be inclined to go for it as well. Just need a first person to do it.

If I could avoid the downtime of having to ship the driveshaft to them, without having to spend $500 on a new driveshaft instead, I'd go ahead and place my order for it and post my impresssions after the install.

And, helldorado, thanks for the info on the different driveshaft lengths. It's important to know.

I may take one for the team and just send ACPT a new 6MT driveshaft in another month or so.

 

Unfortunately that's always the case! Aside from clutches and differentials, drivetrain modifications are still fairly uncharted territory for our cars. I'm already in the same boat for the 3.917 swap, not many people have done it and even fewer have done it for the 5AT. So you end up with a lot of conjecture about the potential and few people willing to risk the investment.

Its too bad we can't help each other out on this one. You having a 6MT and I with the 5AT means we'd need to provide them with one of each driveshaft.

Thanks for providing the direction to APCT. I wasn't aware of them before. If it hasn't been already been done for the 5AT driveshaft by the time I get to it, I think I'm going to budget for that as part of my transmission rebuild.

Hopefully this info helps you out.

 

Just be aware that the torque converter is a torque multiplying device and a manual tranny doesn't have that. I agree, the 3.9 gear isn't too bad for a 6MT, but on a 5 speed automatic that already has excellent tranny gearing plus a torque converter, a 3.9 gear is very extreme plus the gearing will be far from ideal if you do 1/4 mile racing. With the stock 3.36 ratio, you're crossing the line right at peak power which is close to ideal (ideal is solidly in the powerband). The 3.97 gear will put you coming across the line in 4th at a less than ideal 5200rpms. That means the car will have to take time to shift into 4th which hurts your times plus you're coming across near the line in a gear and rpm without much pull. To make the 3.97 gear benefical, you'd need to be coming across the line at 112-115mph.

I guess it all depends on what your definition of "works" is. No doubt will it "feel" much quicker and responsive, but in reality it may be a slower car overall. Years ago, my buddy had an 90 LX 5.0 5MT with some intake/exhaust works and relatively deep 3.73 gears. The car felt extremely stout and could start out in 2nd as if it were like a 1st gear. The car felt ***** fast to 60mph and after that it fell flat. Above 80mph it was a dawg. Another friend had the same car and only a catback, but with some 3.27s. The car felt good, but not near as stout, especially around town. However, when they race, the 3.27 car was quicker once they hit 50mph. At the track, the car was consistently .2 and 1mph faster. That's when I learned about gearing and that my friend's relatively stock 5.0 was overgeared with the 3.73s and 3.27s were more ideal though the car felt quick a bit slower.


If you haven't already done so, here are some rpms and mphs with the 3.97 gears:

At 70mph, the car will be turning about 3000rpms and at 80mph, 3400rpms.

Max speeds @ 6600rpms

1st ~34mph
2nd ~56mph
3rd ~86mph
4th ~126mph
5th ~152mph

 

Agreed, the stock gearing on the 5AT is perfect for the 1/4. I found myself crossing around 6000 rpm with trap speeds in the 94-96 mph range. It definitely maximizes the available powerband and helps numbers rather than slowing them down another several 1/10ths of a second by throwing in another shift. Drag racing doesn't give me much enjoyment, so it doesn't mean much to me except for data collection. Outside of the strip, I think there is a lot of potential for real world gains from this on the street and road course track events. Fuel efficiency and top speed will suffer, but as with most things, its a tradeoff.

Doing the gearing prior to other drivetrain work and engine modifications will give a better baseline in the long run. I'll help me determine what areas I need to improve upon. It'll also help to make a determination on what tendencies we need from a torque converter too. Doing the TC before gearing is a crapshoot, this will give us better direction.

I had already created full conversion charts for my own references. Your numbers are a hair lower than mine, what formula are you using? For reference I used

MPH = RPM / tran gear ratio / fd ratio / ( 5280 / ( wheel diam " * pi / 12 ) ) * 60
Theoretical wheel speed = Engine speed / Final gear ratio / Wheel revolutions per mile * 60

 

The only thing I doing differently is compensating for torque converter slippage at WOT.