I race my 1981 Datsun Sunny with an A12 engine in junior speedway in Western Australia. It has standard gearbox and a 4.1 diff (H145 I think).

On smaller tracks I run 2nd gear with large R13 tires and this works great - it pulls about 8000 rpm at the end of the straights and is just running out of steam - perfect !

On larger tracks though it runs out of steam before the end of the straights and everyone passes me. This is not good.

Toyota Corollas run big R13 tires, 4.1 diffs, and 2nd gear at small tracks, and small R13 tires, 4.4 diffs, and 3rd gear at bigger tracks.

There is no equivalent setup to the Corolla's for the Sunny on big tracks.

This year the rules for junior sedans changed as follows:

Gearbox and diff housing to remain standard for make and model) no cutting, grinding, drilling etc allowed) i.e. Corolla must use Corolla gear box and diff. Ratios are free as long as it fits in correct housing and are OEM. (NOT not to borg warner etc)

My dad says if we could find a higher ratio diff or we could change third gear we'd be in great shape.

Everyone says I should switch to a Toyota Corolla cause they have better diff and gearbox ratios, but I love my sunny and wouldn't think of it.

I've read the tech sections, but no answer found. Any help or insight appreciated

BigRed