Z moves faster than x and y

hi everyone, I 've got a weird case i can't get it solved, would like to have some inputs.
While building up a delta-style printer with ramps 1.4, and marlin, Z axis always moves faster than the other two.
It seems moves more than double the distance than x and y, while x and y moves the same. I've switched them, and it doesn't help, whichever connected to Z port moves same amount faster.
Any one would suggest what's likely the issue?

Are your steps/mm correct for the tower motors? When you ask the printer to move the hotend 10 cm lower, will it really move 10 cm?

Is your delta radius and diagonal rod length specified in the firmware correctly (i.e. there can be at most a mm or two difference)?

Is the hotend moving smoothly when you ask to move it sideways? (If not, then it may be some kind of arduino perfomance problem.)

Thanks for the reply, buddy. Got some clue from IRC, "check jumper under Z stepper driver. should be 3, and check that all have metal in them (Ive seen empty jumpers before), also check soldering of jumper pins " therefore, I tested with another spare ramps. And it is working fine now. though the other ramps has some issue with the end stop pins. Terrible builds, hope it helps the others.

damn ,that could solve my problem, too. I've got X and Y directions calibrated very good, but in Z it's printing about 1/3rd too high every print. I'll check this this evening, I guess there could be a defective jumper, too!