Transmissions and Drivetrain Need help with your trans? Problems with your axle?

what gears should i get

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Old 09-29-2009, 11:29 PM
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Car: 1988 Iroc Z
Engine: SBC 355 crate motor
Transmission: T56 6-speed
Axle/Gears: 7.5 stock Disc rear.
what gears should i get

I have an 88 camaro that im building and im not quite sure what gears to put in it. My crate motor that im puttin in it makes peak horsepower around 6000 rpms, backed with a Tremec 6spd with the these gear ratios.
Gear Ratios: 2.97 1st; 2.07 2nd; 1.43 3rd; 1.00 4th; 0.80 5th; 0.62 6th; 3.28 reverse
I have stock 16in rims on it now but im eventually gonna put on 17s with low pro tires. this car is being built with the turns in mind. Street car with a trip to the track for some road racing every once and a while. Any ideas for what gears i should put in it for superior drivability would be greatly appreciated.
Old 09-30-2009, 09:09 AM
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Re: what gears should i get

I would probably go with a 3.42. It's a very good all around gear and you have a very wide range of gear ratios in that transmission. Are you going to use a Torsen or Truetrac differential? You should upgrade to the 28 spline axles too.
Old 10-01-2009, 10:32 AM
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Re: what gears should i get

I'd have to say 3.73:1s for a 6000 rpm horsepower peak. Not because you need a deeper first gear, or anything like that, but because cams that are big enough to peak at 6000 tend to like a little more rpm when cruising on the highway. Assuming you go to a 275/40R17 tire or even a 315/35R17 tire, which are both 25.7 inches tall just like a 245/50R16, the 3.73:1 would still be just 1964 rpm at 65 mph.
Old 04-23-2011, 07:30 PM
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Car: 1988 Iroc Z
Engine: SBC 355 crate motor
Transmission: T56 6-speed
Axle/Gears: 7.5 stock Disc rear.
Re: what gears should i get

thank you for all the suggestions. since i posted this, i decided to go with a magnum t56. Off the top of my head without looking i forget how the gear choices differ from the regular tremec t56 but if they do, what do you think? i didnt think too much into it but it was just a thought. The corvettes have 4.11's so i had some people tell me to go with that but then again i wasnt too sure how that would work with my setup vs. the LS1. Atilla the fun, more than likely i will go with one of those tire combinations so 3.73's sound good.
Old 04-23-2011, 07:40 PM
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Car: 90 IROC-Z
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Axle/Gears: 3.42 POSI
Re: what gears should i get

If it's still a .62 sixth gear with 4.11 gears you would be at 2300 at 70 mph. SBC like to cruise around 2400 at peak efficency. That is according to horse power tv.
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