In brief, I need to select the gear ratio for my rear axle, and am hoping to
tap some of your collective wisdom.
55 Task Force
Mildly tweaked 350cid (Headers, Manifold, Cam, etc.)
TH-350 3spd tranny, 1:1 3rd gear
Building for 30.9" Diameter rear tires
Churning my calculator, I've come up with a magic number of 761.5: to
convert a Gear Ratio to 70mph engine rpm's. For instance, 3.50 gears should
give me (3.5*761.5) 2665rpm at 70mph.
Now, I just need to figure out what I'd like my highway cruising rpm to be,
and I'll be ready to buy a ring and pinion.
One one hand, a low gear ratio would definitely be a benefit at cruising
speed.
On the other hand, the truck will see a lot more in-town use than highway
use, and just for grins, it would be nice to have a little snap off the
line.
Yeah, I know, in the perfect world I'd change to a 4-speed overdrive tranny
and have the best of both worlds ;-). Then again, I could also put a blown
big-block in it... in either case, if I one day decide to persue either of
those options, I'll probably be able to spend $100 on a new ring and pinion
gear to match. So, for now, I'm focusing on how to optimize for what I
have.
Given my setup, what would you guys recommend as a good compromise? Some
possible alternatives:
ratio 70mph
2.50 1900rpm What my rear end has in it now
3.00 2280rpm
3.25 2475rpm
3.50 2665rpm Common F-150 ratio
4.11 3129rpm Conventional street/strip gears
What would you do??
Ryan.
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