Antz81

I'm doing an iron diff conversion on my 81, and will be changing diff ratio from 2.72 to 3.36. The current speedo gears are 9t drive and 19t driven.
I've done the calculations and come up with two options:
1. 9t drive with 22t driven. (calculation shows 22.5)
2. 8 t drive with 20t driven (calculation shows this to be almost perfect)

Option 1 is my current choice.
I'm curious about which option people think would be best. Option 1 would read a little faster than my actual speed, but this doesn't bother me.

71VetteLover

It's always best to have your speedometer reading a couple of mph too fast to avoid speeding tickets.

BlackC3vette

With either one or two, you could always use a Garmin to verify your speed to see how close it is.

Antz81

it's a good thought. Problem is I always work out how far the Speedo it out and drive accordingly. Only time I ever got a ticket was when I first got the car and the Speedo was reading slow (around 10%)