Speedo gears for 700r4
 

My dad has a 1968 Camaro with a 454, 700r4, and 12 bolt rear with 4.56 gears with a 255/60/15 (27.05in) tire out back. I have gone through numerous speedometer gear calculators and most of them say I am SOL for that gear/tire combo with getting it to read correctly. One website suggested a 19 tooth drive gear and a 34 tooth driven gear. Those ratios were purchased and it was still off. Reading further into things it looks like anything with a 700r4 and over 3.73 ratios is gonna be off without going with a taller tire.

So I have come to the NJFBOA knowledge base looking for suggestions to resolve this and keep the current tires and not convert to a electric speedometer.

Thanks for your help.

Options:

1- remover retarded diff gear to something more sensible.

2 - 44 driven and 13 drive nails it but 700's only have drive gears 15-20 teeth from what I have seen.

With a 1.15% speedo reducer, you can use a 15/ 44T gear combo.
1.45% reducer with a 19/45 combo.
1.5% with a 20/45 combo

Just be sure to order the correct orientation as you need to slow the cable speed down.

The first and last combos are very close w/in 2%

Thank you for your reply, this is becoming extremely frustrating, I never thought this would be such an issue. He wants to keep this gears, the 3.73s weren't enough gear and the 4.56s really seem to put the engine in the happy spot with the trans and it doesn't tach to high on the highway.

Anyways, I cannot find a 1.5% reducer, lowest I could find was 1.3% or 2.56%
http://www.ebay.com/itm/Stewart-Warn...3D361425811123

and

https://transmissioncenter.net/shop/...ratio-adapter/

so now what lol

go electronic

dakota makes a box now I think to drive the speedo.

This
https://transmissioncenter.net/shop/...ratio-adapter/

and a phone.


They can make it. This is who I use. No issues.