Hi o_lampe, thanks for your answer. I have the CRAMPS version 2.2.1 and I think that the servo outputs has been removed.
I measure the current with a multimeter and I never measure more than 1A/48V. In order to measure the current I connected the multimeter on serial with the Spindle and in parallel for the voltage. Also I read in some other place that old 3040 Chinese CNC came with a 50w Spindle that is why I supposed that my results were correct
If it would be possible I would prefer to go for the modification on the MOSFET since witch those params should be possible to use a single MOSFET