4.30 gears

[Beercules]

What do you guys think about going to 4.30s?

With a 0.50 6th gear I shouldn't have issues on the interstate. With everything I've done, it already doesn't have very good milage in town.

Quick online calculation shows I should cross the line a little over 6500 rpm with 28.0 inch MT slicks (28.1 OD).

My biggest fear is the drive shaft (aluminum) already starts vibrating at around 100 mph with 3.90s.

 

[1 Alibi 2]

What do you guys think about going to 4.30s?

My biggest fear is the drive shaft (aluminum) already starts vibrating at around 100 mph with 3.90s.

.
Something isn't right, fix this before you worry about gear changes !!

 

[Beercules]

Ok, maybe ill just order custom CF shaft, have 9".

 

[RedVenom48]

FRPP 4.10s are a great gearset. With my factory 27.9" diameter SVT rear wheels and tires, Im cruising at 2200 RPM at 80 mph. Last trip to CA from Phoenix, I was averaging 20 MPG.

Id personally stick with a Ford Racing set hence the 4.10 recommendation.

 

[biminiLX]

Ford racing makes or used to make a 4.30, I ran them in my '01 Cobra.
I also agree you shouldn't have a vibration issue, and if you don't plan on adding huge power, yes 4.30s would be perfect in a street/strip car.
I trap about 71-7200rpm with 4.10s and a cammed 960rwhp.
To optimize your combo, 4.30s would be great, better than current 3.89s.
Your slicks will also grow to over 28.1" at trap rpm (guessing 140mph?)
With a 2.66 first gear and 0.50 6th yes you're correct these cars respond really well to aggressive rear gears.
-J

 

[Beercules]

Ford no longer makes 9" gears. Have to go aftermarket.

FRPP 4.10s are a great gearset. With my factory 27.9" diameter SVT rear wheels and tires, Im cruising at 2200 RPM at 80 mph. Last trip to CA from Phoenix, I was averaging 20 MPG.

Id personally stick with a Ford Racing set hence the 4.10 recommendation.

 

[biminiLX]

Initially missed you hav a 9" but good news lots of places do make them.
4.11-4.30s are great 9" choices if you have traction.
My 29" tall tires and 4.10s are 2000rpm at 80mph so another 200rpm will barely be noticed.
-J

 

[Beercules]

It's amazing how we still get 20mpg with all the mods we do.

FRPP 4.10s are a great gearset. With my factory 27.9" diameter SVT rear wheels and tires, Im cruising at 2200 RPM at 80 mph. Last trip to CA from Phoenix, I was averaging 20 MPG.

Id personally stick with a Ford Racing set hence the 4.10 recommendation.

 

[Beercules]

The strange thing with 9" gears, summit starts asking pinion size when shopping.
And 7.33 gears??? Damn!

Maybe 4.30s won't bog at the line.

Initially missed you hav a 9" but good news lots of places do make them.
4.11-4.30s are great 9" choices if you have traction.
My 29" tall tires and 4.10s are 2000rpm at 80mph so another 200rpm will barely be noticed.
-J