Rear ratio difference


Founding Member
May 1, 2002
Granada Hills, California
I already asked this question once, but is there a significant difference between a 3.50 ratio third member and a 3.25? I would go 3.50 but I'm afraid I could see driveability problems, excessive gas consumption and it being too aggressive for my engine. Any comments? The car will be daily driven and probably won't receive serious engine upgrades until at least next summer, but I'd like to get the car into the 14s by taking what I have below and adding a posi rear with some gears.
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I did some calculations to figure engine RPMs for you.I don't know what the diameter of your rear tires are so I did the calculations using a 26" tall tire.

At 55mph with 3.25 ratio engine RPMs are 2310
At 55mph with 3.50 ratio engine RPMs are 2487

At 65 mph with 3.25 ratio engine RPMs are 2730
At 65mph with 3.50 ratio engine RPMs are 2940

Using a 27" tall tire drops rpms about a 100rpms
using a 25" tall tire raises rpms about 100rpms

If you want to figure other ratios and tire sizes the formula is:

(Gear Ratio X MPH X 336) / Tire Diameter = Engine RPMs

This formula is for non-overdrive transmissions.

Hope this helps out. :)
3.25 IMO

There is little difference.
You have a fairly light car.
You should have gobs of torque.
Your intake does best at very low revs.
You daily drive.
It all adds up to 3.25s by my calculations.

Do you have an aftermarket cam?
If so, duration @ .050"?
Okay, stock cam just makes me more certain on the 3.25s.
You can actually lose useable power with a short gear and stock cam combo. Add the Performer intake and you would hate any gear much lower than 3.25.