tranny question
Thread Starter
Instructor
Joined: Aug 2007
Posts: 224
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From: SHERMAN TEXAS
tranny question
which tranny (close or wide ratio ) for my application. i have 370 gears im thinking of finally pulling out my leaky th 400. i want it to pull hard and fast through each gear
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Yep, it depends a lot on power/torque curves and your purposes. That said, assuming your engine isn't a complete dog (in which case gearing won't really solve the problem anyway), the general rule of thumb is ~10:1 total multiplication in 1st gear on C3 stock'ish diameter tires.
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
You should be fine with most commonly available gearsets, since you already have 3.70's out back, but if it were my call I'd avoid steps of very much greater than ~40% between any two gears especially 1st to 2nd.
My reasoning is, while you might be theoretically OK shifting at no less than 5400 RPM from a 3.33:1 1st to a 1.85:1 2nd (a 44% step) to keep from dropping below 3000 RPM, you may not wish to drive that way all the time to stay in your engine's optimal power band. Besides, huge 1-2 steps are really a bandaid for overly tall rear (low ratio) rear gears, and you don't have that problem.
Bottom line: I'd shop for a 5-speed with no more than ~3:1 1st that otherwise meets your requirements, and not get too caught up in ambitiously tall OD ratios, hypothetical performance wise.
My reasoning is, while you might be theoretically OK shifting at no less than 5400 RPM from a 3.33:1 1st to a 1.85:1 2nd (a 44% step) to keep from dropping below 3000 RPM, you may not wish to drive that way all the time to stay in your engine's optimal power band. Besides, huge 1-2 steps are really a bandaid for overly tall rear (low ratio) rear gears, and you don't have that problem.
Bottom line: I'd shop for a 5-speed with no more than ~3:1 1st that otherwise meets your requirements, and not get too caught up in ambitiously tall OD ratios, hypothetical performance wise.
