Hmm... I don't think that the WHP increase corelates eith the percentage of gear leverage increased.

I would think that by the seat of the pants you could feel a definite difference though.

To put it into perspective, I don't think that you could expect 400 extra ponies at the wheels from a 4000HP top fuel car by up-ing the gear ratio 10%. It's an extreme, but helps demonstrate how the two percentages are not equal.

Then again I could be wrong... Good discussion point Spy.

I was just reading an article in SCC this past week about gear ratios (Technobabble, July 2005). In this article the author was discussing the effects of switching transmissions to different cars and their final drives.

This is where it's pretty cool. Transmissions and final drives ARE actually torque multipliers. Example: This article was about swapping a rare Autech SR20 DE (Nissan 2.0L DOHC) with a 6 speed tranny from a S15 Silvia into a Mazda Miata using the stock rear end with a 4.3:1 rear gear. He ranted into putting all the revs from the motor divided by each gear and then divided by the final drive. This number was multiplied by the circumference of the wheels being used. All this was to find wheel speed for each gear at every rev.

Next, he used dyno information to determine the torque at the wheels. The selection of the final drive alone can affect these numbers.

So, yes, this does indeed give you a higher amount of torque. And it will actually give you more all across the board because you altered the one gear that affects the output in every gear.

You'll never ever see a difference in WHP with a gear change.

Going 10% up on gearing just means you'll transmit 10% more torque to the wheels with a 10% loss in the top speed of the gear.

In a given gear, ignoring traction, the car with 10% more gear will accelerate exactly 10% more quickly due to the extra torque.

Gears don't always translate to better times, even with infinite traction. Most turbo buicks slow down several tenths when switching from 3.42 to 3.73 gears from having to shift into overdrive to finish the quarter.

Ideally you'd grab your dyno sheet and set the gearing up so that the car crosses the line just past its HP peak in your gear of choice.

this is good info to think about... I know that most of us think about this when we are trying to build the car however... how do you get to this figure?

are we talking about using a desktop dyno (or chassis dyno) to find peak torque/power output then calculate 1/4 mile times based on those numbers and then calculate acceleration and distance per gear to determine speed at the end to determine what gear to run in the end????

sounds pretty complicated with out a big fat greek wallet!!!!

then again if I did have a big fat greek wallet I would just dyno my car, rent a track for a weekend and then switch gears every pass to see what gear accually yeilded the best results.