Hi!
I have a T56, 6 speed trans on my car and the rear axle ratio is 3,54:1. Wouldn't it be better with something around 4,00:1?
5th gear is 0,75 overdrive and 6th is 0,5 overdrive.

The car isn't on the road yet and I'm wondering how much time I should use to track down another rear axle?

Motor is a near stock CSB.

 

Most people go with a 4.11 or 4.10 gear with that trans. With that much of an overdrive it shouldn't hurt all that much. There are calculators that will tell you the motor rpm at whatever speed from trans ratio, axle ratio, and tire height.

 

What kind of rear end do you have? Ford 9"? Lots of selection in that...

As mentioned, 4.10/4.11 is common. If you don't intend on cruising at 120+ MPH, you can go even higher (4.56 or more). Depends on tire height too. Looks like you've got tall tires so...
What the heck is a CSB?

Nothing wrong with 3.54, you just won't have the snap off the line.... Or the fun of shifting out of first gear at a blazing 3mph ...

 

Chevy Small Block maybe.

 

Hi and thank you for your inputs!

The car is a fenderless 34 Ford roadster. The reason I ask at this board is that you are much more familiar with the T56 transmission than the guys over at the hotrod boards.
And It is a former Roadmaster L05 Chevy Small block (CSB) in the car too. Rebuilt to carb, but still a motor well known to you here at thirdgen.org.
Hope it's ok.

The rear axle is a Jaguar IRS unit by the way.

 

I've never heard anyone refer to it as a "CSB"... Most places call it a SBC, Small block chevy.
But ok, I gotcha...