Gear Ratio Help!!!!!

[l_and_t_reproductions]

I am looking to upgrade to a ford 9" (spare the debate on which is better 12 bolt v. 9" - that decision has already passed :nopity:) but need to decide on a gear ratio before I can make the purchase. Can someone help me with what ratio would be best?

Car Stats:
I am running a 4L70E/LS2 combo from a 2007 Trailblazer SS donor with no mods - in a 69 camaro with a curb weight of ~3400lbs.
The stock trailblazer used a 4.10 gear but I think that may be a little much for the camaro given the weight difference (4700lbs v. 3400lbs) and the fact that the car will be 80% street and 20% track (hopefully!).
I have read that the stock motor/trans combo has a 2100 rpm stall.
I would like to have a cruising RPM of around 2200 - 2400 but I think that equates to a ratio in the neighborhood of the 3.40s.

What does everyone recommend?

[Dantigan]

If you know your tire size you can find a gear ratio calculator online and input the final engine speed you want and it should help narrow it down.

[SRD art]

Searching wrecking yards for a 9" for my car I found 3.50s is a common ratio for for a stock 9", particularly in trucks. I think that would be a great everyday ratio with an overdrive trans.

I agree with Daniel, find out where your cruise rpm range is and make a determination. I'm not sure that weight will affect your driving rpms much when compared to tire size and final gear ratio. Technically speaking a trail blazer and a Camaro with identical drive trains and tire diameters should cruise at the same rpms. In this case the Camaro may only accelerate faster because it its lighter.

For example purposes, my son's Nova will be running 3.36s with a 5 speed and 26" tires so his gas bill is a little less. I'm looking at running 3.70s in my wagon's 9" for a little more acceleration on a 25.5" tire.

My street strip Nova currently runs 4.56s on 28" tires. Around town with a TH350 3 speed, the Nova "feels" like it's stuck in 2nd gear- even though it's in 3rd, and does about 3600 rpms at around 60-ish mph. An overdrive trans in this car would bring the final ratio to about a 3.20 gear and a lot more bearable on the street.

My wagon on the other hand with a 25.5" tire, factory 2.41 gears, and a TH350 3 speed runs around 2200 at about 65 mph, almost like having a steeper gear and an overdrive. Off the line acceleration with the 2.41 gears suffers though. Actually it's pretty pathetic.

[TheJDMan]

I'm running a 3.50 gear with 26" tires. At 55mph my engine RPM it 2500, 60mph is about 2700. I think this is about where I want to be.