NO you are not replacing a "gear" of the transmission as in 1 2 3 4.
You are replacing the FINAL DRIVE or the final set of GEARS, not to be confused with clutch packs that are "gears" of the trans among other things. This FINAL DRIVE is the last rotation before another shaft that spins energy towards the axle, anyone feel free to correct me if i'm wrong. It's been a while since ive touched or cared for an A60 .
By changing the FINAL DRIVE ratio, are you with me?, you increase or decrease acceleration. Just like any sort of gear set, if you have equal amount of teeth on each gear it will spin equally {duh}. If you have a different amount on one teeth from the other, the spun or spinning gear will turn faster or slower depending on the number ratio.
Now I havnt counted the teeth on the stock or FINAL DRIVE GEARS but people are doing the mod and increasing acceleration so i'd say it's a good ratio to have. Much better than stock anyway.
Go to howthingswork.com or howstuffworks.com whatever it is, either one will take you to where im talking about, and learn about gears and gear ratios. It will help you out a lot in your auto journey. Also go read up on how AT transmission work, that will also help with the knowledge you need to know about an automatic.
Joseph
PS - I repeat, you are not changing any "final gears" in your transmissions such as 4th gear. I am only saying this because you said "we dont even reach our 'final gear' at the track". I assume you meant 4th gear. The FINAL DRIVE GEARs are at a constant spin if you are moving.
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