unknown_host

iTrader: (1)

ok guys its not my daily driver and i plan on some street duty but not a lot, more like once a week for fun. i was talking with some friends of mine who are drag racers who think i should get 4.11's. i was thinking 3.73's. i have 350HO GM crate motor, 330 horsepower and 380 torque, redlines at 5700 rpm. if i have 275/50/15's and i wanted to only wind the motor to 5500, that would put me at a top speed of 103 mph before i hit redline. you think 4.11's or 3.73's. i have heard of people getting 3.90's, where can you get these.

92superram

3.90's would be about perfect. I don't think they make them for our rears though. You could call richmond, or some other gear manufacturar, and see if you could get some. A 410 would only run a few hundred rpm's higer than 3.73's on the highway, but I would say if you have an overdrive tranny go with 4.10's, if not go with 3.73. It is all up to you though.

AlkyIROC

I agree with the 3.90's but that isn't going to happen unless you decide to use a 9". Go with the 3.73's. If you're shifting at 5700, you don't have enough RPM to get the full potential of 4.10's.

Actually you want to be at redline a couple of hundred feet before the finish line for a good setup.

Gear ratio will also depend on the tire size you intend to use. If you're using a relatively stock height of 26" then 3.73 gears. If you go to a taller tire height of 28" then 4.10's would be better. Those 275/50/15's are 25.8" tall

curt86iroc

my friend has 3.90's in his 76 camaro with a th350 and a 355. his top speed is around 115 i believe before he goes past 5000. i think his rear tires are 275/70r15.

unknown_host

iTrader: (1)

damn 70 series 275's lol. those are tall.

paul_huryk

The statement above is not correct, if you do so, you will not still be pulling as you are at the traps, essentially cruising to the end (from the point you hit redline).

The absolute best gearing gets you across the traps exactly at peak RPM, which in your case is 5000-5200rpm (unless you changed the power curve). If your motor has 330hp and the car weighs 3600lbs, you should be going about 106mph (theoretically) and that would require a 3.73 gear with your tire height. Keep in mind that converter slippage may add a few hundred rpm (the higher the stall speed, the more slippage) to the trap RPM.

Another thing to keep in mind is the fact that if you gear a car for the motor alone, it no longer becomes effective if you used forced induction or nitrous. If you add 100hp NOS to a car that already runs 106mph, it will go about 116mph, which means the revs go way up (400 or 500rpm more), with the same peak power rpm. If you have a 9", you can change the gears very easy; if you have a normal rear, it not not easy (or fun, or cheap). Keep that in mind when you select gears always. I would say go for 3.42 gears with the notion that you would accomodate a mild power adder without having to re-do the gears. The difference between 3.42 and 3.73 gears at your power level (on the motor) is max 2 tenths (probably like a tenth). You will drop your highway revs a few hundred also.

ATOMonkey

No, he's right about finishing up a little higher than your shift point. Just a little though, like a couple hundred RPM. You don't want to be pulling at the light, you want to be done pulling at the light.

Besides that 4.11 TH350 combo is as old as racing. That's what everyone and their brother runs.

AlkyIROC

That's why I said a couple of hundred feet before the finish. If the car is geared correctly the rpm increase in that last 200 feet will be very little. 100-200 rpm at the most if that. You want to see that shift light come on before you cross the finish line.

lankchevy_350

umm not trying to start anything but atomonkey if everyone and there brother uses a th350 and 4.11s dont that kinda tell ya something? maybee cause its a proven winner.

kolby

i might have misunderstood that but it sounds like u are saying that th350/4.11 is outdated and u dont want it or something along those lines

ATOMonkey

No, actually I'd perfer it to the slip-o-matic 700. Not saying that the 700 is bad, it's just a little too new for the aftermarket and serious trans guys to be familure enough with it to mod it to the 600-700 HP reliable range, like a th350-400 will handle. BTW after my bro kills his 700 that he had built we're doing the Turbo Hydromatic boogie. I just grew up with drag racing and street racing, and my dad tells me everyone was running a 350 camaro/nova with 4.11 gears. Just works out that a car with a 28ish inch slick and a 7 grand ish engine finishes well with 4.11s and still has decent street manners. All the t56 4th gen guys swear by the 4.11s as well.

primer84z

ive seen many 6 speed 4th gens with 4.56 rears. works excellent at the track and can still cruise at highway speeds at a tolerable rpm.

unknown_host

iTrader: (1)

*** 1st gear on a T-56 with 4.56's must be like less than 5 mph lol.

F-BIRD'88

Go with the 4.10's