Happy ending
Thanks guys, you were all correct.
don@transmissioncenter.net who supplied the gearbox sent me free of charge a blue speedo gear and that fixed the problem.
I had the official Swiss Government 3 year vehicle test today and it passed the speedo check. Surprised me because according to my GPS it is still 5% slow.
Just to be safe and to be sure I got the part before the official Swiss Government 3 year vehicle test, I also ordered a blue gear from
http://www.crt-performance.com/speedometers.htm. They were very helpful and it also arrived in time.
So I guess I will be laying some speedo gears into ebay today.....
Marton