How to fix speedo reading to fast

[Jingles56]

Hi guys I've got a Datsun 1600 that reading 10 mph to fast.i have to do 70 to do a genuine 60 and 35 for 30.im running a short shaft dogleg 5 speed and on 14 with 195/45/14 tyres.have been trying to google what others have done but can't find anything.someone did say bout a calibration box bout think they really dear but could be wrong and changing speedo cog but not shore where I'd find any cogs to test.need to get it right cos I've got cert coming up and it has to be with in 5%.any help would be much appreciated

Thanks James

[classicdat]

You have 2 options really, get the speedo calibrated, or fit a drive that would suit a lower ratio diff, see This build thread:
http://www.nzdatsun.com/forums/viewtopi ... our#p47353" onclick="window.open(this.href);return false;
Scott at Cockrams may be able to assist if there is nothing available second hand.

[Jingles56]

Ok it looks like I need a blue cog for it as if got a 3.7 diff in it.anyone no what gearbox the blue cog is in or where to get.ive got an old dogleg and it's yellow and a 4 speed.think dogleg is 19 tooth and 4 speed is 16tooth