I took the gear out again yesterday and photographed it with my mobile phone and measured it. It's was orange not white as I said before and it has 35 teeth.

I have contacted the guy I bought my speedo gear from Ebay and he says I have the large housing and orange gear goes from 34 to 39 teeth. He says that one tooth larger corects for about 3.5 mph. I am about 20 mph out at 40 mph as my speedo is reading about 60 mph when I matched my speed with other cars in a 40 mph speed limit so this is only a rough estimate of how far out the speedo is.

When I was in a 70mph limit I matched my speed with other cars and my speedo was reading 100mph and when I went about 80mph it was 120mph. So If I go drag racing I am going to be doing about 95 to 100mph across the line so my speedo will be off the scale! Does it just keep going round or will it break.

He also says that If you I go to a 40 thru 45 you must change the housing too. I also may have to change the drive gear.

I was going to see if I can get a 39 tooth gear as that would correct 17.5mph and that may be close enough.