What rear gear ratio?
- Thread starter slowestmonte
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When swapping out gears, you also gotta think about what size tire you're gonna run. With 2.41s and a TH350 and 195/75/14 tires which are 25.52 inches tall, my car ran at 2000-2200rpm at 65mph on the highway. If I went to Regal T Type wheels which are 15x7 and use a 235/60/15 tire which is 26.10 inches tall, it would do less revolutions per increment of distance than the smaller tire would. With the taller tire, and no other changes, I'd be doing maybe 100rpm less at that speed. But, if I change the gears out back to 3.23 for example, with the 25.52 tires it's now 2800rpm at 65. But, you're lucky. You have OD to shift to on the highway. Instead of being 1:1 like 3rd in a TH350, OD is .067:1, so with the 195s and 3.23 gears you'd only be at 1800rpm. Just something to think about.
I agree, especially with the stock 305. I am still deciding between 3.42's and 3.90 gears on my 70S. Even with 3.90 gears with slightly taller tire, I will still run at 400 rpm less with the converter locked over the TH350.
I prefer to look at the total package. Tire height, rear axle ratio, overdrive ratio, and first gear ratio. I like to shoot for about 2500 RPM in overdrive at 85mph. I plan to drive my car cross country so I want to be able to get down the road without turning 3000+RPM. My setup is a 3.08 rear gear, 27" tall tire (235/60/16), 0.78 overdrive in a WC T5. Should be about 2500 RPM at 85. A 3.42 would bump that up to 2800 RPM. A 3.73 up to 3100 RPM. First gear in my T5 is 2.95 which is a little low but that works well with the 3.08 that is in the car. 3.08x2.95=9.1 final drive ratio in first. Should be quite comfortable on the clutch.
I realize this thread is not about my car. I just wanted to illustrate how I like to look at the entire picture to determine what I want. It all comes down to how the car will be used.
I realize this thread is not about my car. I just wanted to illustrate how I like to look at the entire picture to determine what I want. It all comes down to how the car will be used.
Love your username, and your car. I believe everyone is right is 3.08 is the highest(in terms of performance) you can go. I have nearly the same car now(85) and I just swapped to 3.73 with a series 3 carrier and posi. I'm trying to working out some transmission glitches but the little I drove it 3.73's seem like a bit much for me. 3.08's or 3.23 seems like it would have been a better choice.
are you sure you have a .78 5th? By this chart they never put a .78 in a GM WC. I have a .73 in one of my T5 WC and a .68 in the other.. With my .78 5th at 75 mph with 26.65" tall tires and a 3.08 rear I am at 2000 rpm
http://www.britishv8.org/articles/borg-warner-t5-id-tags.htm
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