Whats a good gear for a big block Chevelle that produces about 525 horsepower and is in a 4200 pound car? I have a Turbo 400 tranny and I'm looking for a gear ratio that will give me good performance at the track and on the street. I drive this car to car club meets, but thats rare. I would like a 4.10 or a 4.56. How do these gear ratios react on the street? I'm hoping that someone has done this before and I don't have to make any mistakes. It currently has a 8.5 10-Bolt rear end with 3.42 posi, but it's not enough.

73CSS,

I run a 4.10 in my '72 Chevelle, that I'm guessing weighs 3800. My engine is also a BBC that makes about 520HP. Rear tires are 28x12.5x15 M/T street slicks. I drive this car about 3 times a week and have never had a problem with this gear ratio. However, your slightly limited on the freeway, at 60 mph I'm doing 3100 RPM's. IMHO, that's the only draw back.



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Joe Giniel
72 Chevelle SS
Team Chevelle #143
Aces #03056
West Bloomfield, MI

It really depends on your rear tires & traction. What is your shift rpm & rear tire diameter?

[This message has been edited by SirVette (edited 12-22-1999).]

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[This message has been edited by Sean (edited 09-22-99).]

With the torque of your B/B, You can get the best of both worlds without killing your freeway driving.
I have had very good results with 3.73 gears and 28" tall tires.
If you are looking for better 60ft times and are otherwise happy with the gear you have, look into your converter stall speed.

Sean

73CSS, my compromise gear for my 427 67 Chevelle is a 3.90, but if you don't do any highway driving at all, the '56's would be mint for the straight line.

Gene, it's good to hear about the 3.90's. I tried running my 454 with 4.56's and a 28" tire and it was even too much at the strip. My engine isn't set up to be buzzed, so i'm going to try the 3.90's next year so I have motor the entire way down the track! The 4.56's were also untolerable on the street.

Doug, the 3.90s never made it it. Still with the 3.55's n changed to a M20 tranny first. We'll see next year. If it doesn't crack 12.5sec or 7.5sec in the 1/8, I'll step it up.

Maybe I'm just getting old (35), but I like 3.23's up to 3.55 for a high torque Big Block. I had a 4000rpm converter, 4.10 gears and a big solid cam in my 396 years ago. It went faster with the 3.73's at the strip. I have 3.08's now with the 440hp 502 that I installed in '97. I couldn't go anywhere with more gear! Spin, spin, spin. I can't adjust the rear suspension any more to get the tires to plant with more gear. I love the 3.08's with the monster torque I now have. When I get it all bolted back together with the new motor, I'll let you all know how it performs with the small gears. Most big blocks were not meant to spin to the strotosphere. Torque Rules! My $0.02.

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1970 Chevelle SS Clone 502-540HP-560ft-lb
1992 Trans Am Conv(4Sale)
1992 Taurus SHO
Mercer, PA
sswinger.home.att.net/ (http://sswinger.home.att.net/)
sswinger@worldnet.att.net

What do you like?

I've run 4.56s for the past several years. On a long road trip they're a complete drag, but around town they can't be beat (literally!). If big gears are what you're looking for, give it a try and see how you like it.

Sam, what kind of '60 times were you getting with your 3.23's vs. your numerically higher combinations. That option sounds very attractive. I'm surprised that going with a numerically lower gear actually helped your tire spin problems. It seems I have always heard the opposite in the past. When you say you went "faster" do you mean ET or MPH?

I've got a 427, T400, and 4:10 gears with 28" tires in my '73 and it seems to work well.
I'll give you some more detailed info if you want.

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Sean Flanagan
Heavy '73

I have a 3.31 rear with a super T10 with a 2.64 first gear. I still keep reaching for another gear when I'm on the highway. I will look into a 5speed with a 2.5 to 1 rear. I set my engine up for low end torque not a high revin screamer

I went from 3.31's to 3.73's and am happy with the results. I'd drive it a few hundred miles if I had to, but wouldn't try the 500 miles to the Chevellabration. Is that 10-bolt going to hold up to 500+ HP if you floor it?

I think Doc brought up a good point. Your pushing over 500 HP with a TH400 (and maybe a stall) and a posi 3.90-4.56? I know the 8.5 inch 10 bolt is a strong rear, but if you went the extra mile getting that 500+ HP I think you should look into a 12 bolt. Just my .02

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IrateN8
Northern California
1970 Malibu Sport Coupe, Proudly USA (TX) Built
Gen-X Member