2.66 low gear vs close ratio

Short stroke street SBMs, in A-bodies,like a starter gear around 10 or 11 to one. so lets average that to 10.5; then 10.5/ 2.66low gear = 3.95, rounded to 3.91 rear cogs. What?! you ask. Yeah I know that's out there. I said like, not have to have. 3.91s will be a dump the clutch, and drive experience;something your 16 year old daughter can drive away. It will launch hard. Now 10.5/3.09 =a rear cog of 3.40. Hence why I use 3.55s with my 3.09low box. The short stroke SBMs will suffer your 8.59 ratio; with a "bit" of slipping to get going, and once up to about 2000rpm, they're ok. So the target street starter gear, might be in the range of 8.59 to 10.5; and thus a middle of the road ratio would be 9.55. And that divided by 2.66 = 3.59s-rounded to 3.55s.That is why 3.55 gears are so popular.

Oh yeah the 360s, for the same application,can use 340/360=.95 as much ratio; so .95 x 3.59 = 3.41 rounded to either3.23/3.55s. And teeners; 340/318 = 1.07 as much ratio; so1.07 x 3.59 =3.84 rounded to 3.73/3.91s.
And the reason for the starter gear difference? You guessed it;Inherent torque.This generalization sorta works for all street sbms, cuz thats all I know.I say sorta cuz it spits out; 340/273 x 3.59 = 4.47, rounded to 4.30s. Well that might be a lil excessive, unless our lil orphan brother was running a cam on the big-boy end of street.
Anyhow,that's my measuring stick, and makes for a happy driving experience, with moderate street cams.
The smaller your cam the smaller your rear gear can be. And vice-versa. And since you have an adjustable stall(clutch), you can run a too-small cog. It just takes a bit of concentration at the start-line.Or a bit of flywheel. Now, the too-small cog will,at any given moment, be putting down less torque to the pavement, so you can expect a slower rate of acceleration, but this is really only apparent at WOT, cuz the rest of the time you will be adjusting the torque output with the gas pedal.But there is a good chance that hi-way gears behind a cammed teener will always feel like you are in the next higher gear.And that's cuz you sorta are.The engine doesn't know anything about gears. It only knows about torque multiplication. Whether the rear is 2.66 and the tranny is 3.09, or the rear is 3.09 and the tranny is 2.66, it cares not a wit; it sees only 2.66 x 3.09 = 8.22 torque multiplication. So then, if you have the 2.66 low box with .72 splits, then a change in rear cogs of that very same .72 split, will feel exactly like you are in one gear different. Example;2.76/.72 = 3.83. If you swapped out your 3.83 gear for 2.76s, you will always feel the one-gear handicap.
Ok but an increase of engine torque of that same split, would put you back on an even keel. An across-the board increase in engine torque of 1/.72 =about plus 39%, would even the driving experience. So then 1.39 x your engines torque x the small cog multiplication would equal 1.00 x your engines torque with the big cogs. Unfortunately plus39% is a huge change in across-the-board torque;akin to supercharging, or engine swapping. Big-engine engine swapping.

Long story short; If you want your car to perform sporty, you will need sporty torque multiplication. Whether it's in the cogs or in the tranny, the engine cares not. An extra gear in the tranny trumps swapping chunks for a roadtrip.



There is a fellow selling a 3.09low box right here on FABO, right now........