67HEAVEN

I don't know if this sort of thing will be of any use to you, but one of the steps in my '67 project was determining the transmission and rear gear to use.

I didn't want to sacrifice any "ooomph" away from the stoplights, but I also wanted to keep the highway revolutions down.

Here's how I decided.....


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:chevy

Les

Nice job- I'm sure that's going to help out a few of the folks here! :cheers:

WA 2 FST

Bob,

Looks great to me! :) This is exactly how I always go about choosing rear gears for a car.

People who just haphazardly throw different tire sizes and rear gears in their car always have me shaking my head. Usually, its guys who run too short of a tire and way, way too much rear gear...and then they wonder why they hit redline in high gear at 100mph. ;)

Anyway, I'm sure you'll be happy with your choice of trannies and rear gear ratio. I would have gone with a 6-speed, but for me it wasn't worth the extra $1k, as little highway driving as I'll do with this car. Plus with the 3.36 rear gears I'm turning 3000rpm at 70mph, so its not too bad.

I may end up stepping down to 3.08s in the rear like you, if the power is just too much for the new rubber I'll be getting soon.

Let us know how you like the 5-speed! :)

75 BBC Stingray

I took a look at the table you set up. I don't understand why there is only one column for speed. Wouldn't you want to look at speeds for most of the gears?

I was thinking just today about how to decide exactly what ratios I wanted. My thoughts were to look at the speeds where I spend most of my time and look for gearings that would support these different speeds at lower engine RPM's. I'm sure some comprimises would be in order, and I haven't crunched any numbers yet, but here's what I was thinking:
65-70mph (highway)
55-60mph (highway)
45-50mph (back roads)
I would try to select the last 3 gears to give me these speeds at approx. 1,500RPM. The first two gears would be decided based on a tall enough first gear so I would NOT spin the tires too easy, and the second would be what I could find to bridge the gap between the first and third gears... How's that sound???? :confused:


[Modified by 75 BBC Stingray, 9:21 PM 12/27/2002]

Chuck Harmon

67Heaven,

Yup, that's the same rationale I used and I came to the same conclusion. I calculated the mph in each gear at redline too. I think you'll find that with the 3.08's and a 3.28 1st gear you have virtually the same overall ratio as a 4.56 rear end with the M22 rock crusher in fisrt gear. And you will still be able to run with a ZO6 when it comes to top end!

Chuck

67HEAVEN

75 BBC Stingray,

With the kind of torque, horsepower and radical cam I'll be running, the only issues that I was concerned about were:

1. keeping from bogging without burning away from stoplights; and,

2. keeping revs at a reasonable level at highway speed limits.

Each of you will have your own criteria. Good luck. :seeya