Z-Speed too slow

Hello,

I have an Mendel Max printer with dual extruder
I uploaded the current repetier firmware, everything works but the z-speed. its extemely slow, and the step are wrong i think. (insetead of 10mm, the z-axis lowers only 1-2mm)
what have i done wrong? the steps are for the m8 rod-z-axis are 2548.