So I have a 36 VDC motor rated 70 A at 2000 W (mechanical output power).
I would like to run the system at 48 V (same power) because I have a lot of accessories for 48 V systems (battery chargers, DC/DC converters, motor controllers). Is it possible to overvolt the motor by 12 V (30%) if the current is decreased by 30%?

I was taught in school that the voltage rating is related to winding insulation, and I *think* 36 V insulation is capable of carrying 48 V. 

Is my assumption correct?