Rear gear ratio question

[litebulblsc]

I am considering a different gear ratio for my truck. Currently has 3.73:1. Playing with an online calculator, I could go down to 4.56:1 and still be able to get to 135 mph in 3rd. My fastest trap was about 118 mph, and I can only add so much more power with my current setup, that I do not see me hitting 135 mph in the quarter.

So is there a reason not to go with the lower gear ratio? It should make the truck faster, correct? The only down side I can think of is traction,but their are ways to overcome that.

[Getter-Done]

You could go with a 5:14.

The math is there.

[regan wilson]

A lot of things come into play on choosing the right gear. Tire size, transmission gear ratios, tq converter slip, max rpm etc.

[litebulblsc]

Originally Posted by Getter-Done

You could go with a 5:14.

The math is there.

I am aiming to up my mph some. That would put me at "redline" at the stripe with the convertor locked

Originally Posted by regan wilson

A lot of things come into play on choosing the right gear. Tire size, transmission gear ratios, tq converter slip, max rpm etc.

Tire is 29.5
Trans ratio would be 1:1
I have a lockup convertor, so slip could be zero
Max RPM is 7000

With those numbers it comes out to about 135 mph at 7000 rpm.

[68racer]

I calculated that changing from 3.7 to 4.1 would give me a tenth or two. It made no difference at all, although it became more consistent. These trucks hit aero problems at the top end.

[regan wilson]

I think 4.56 will work. Especially with the lockup converter.

[Ziegelsteinfaust]

I run 4.88's daily with a Detroit locker in a 32" tire. Or a 285/65R17.

To me the biggest hold back of the combo is the TH700R4. If I had the money's to do over. A 4L80e would of been a more optimal choice.

Even though my engine is just a highly tuned gen2 LT1 it is a absolute blast to drive. I do miss the way bigger cam I had before. If I replace the cam it will be with a smog legal performance cam to get a little more out of her, but keep my drivibility.

My gear ratio, and Detroit effectively stop me from burning out. So that would be good for the 1/8 mile.

The same gear ratio hurts my top end charges a bit because my engine is more torquey vs 4500 rpm plus performance.

So with out mentioning engine specs or build list, and tire size.

Even 4.11's or 4.33's maybe a better split the difference overall combo.

[litebulblsc]

I ordered the 4.56s and a detroit locker last week. Can't wait till the Spring to try them out.