Hermanelfino, have you checked the Wiki page about maximum step rates?
IMHO you are simply trying to operate the M8 Y-axis at a step rate which is way to high for the Marlin/Mega setup you have.
With 2048 steps/mm you will reach the safe limit of 10000steps/sec at about 5mm/sec - so I wouldn't even trust the 8mm/sec you are using.
This has nothing to do with the stepper motors you use, it's the Marlin software on the 16Mhz Mega that reaches its limit.
IMHO you are simply trying to operate the M8 Y-axis at a step rate which is way to high for the Marlin/Mega setup you have.
With 2048 steps/mm you will reach the safe limit of 10000steps/sec at about 5mm/sec - so I wouldn't even trust the 8mm/sec you are using.
This has nothing to do with the stepper motors you use, it's the Marlin software on the 16Mhz Mega that reaches its limit.