Vibration when running X and Y at same time

I had another thread going on x axis vibration, but figured some things out and wanted to focus on the outcome.

I can replicate the problem with manual gcode if I move both x and y axis at same time:
G1 X76.270 Y74.420 F720.000

if I run this:
G1 X76.270 Y74.420 F4800.000
its not as bad.
The slower the speed, the worse the vibration!
Also, my steppers get warm fast. How hot should they be getting in say 30 seconds of constant xy movement?

My stepper drivers are cooled well by a fan, as well as ramps board, so should not be a heat issue there.
Any ideas?

my accel. settings in configuration.h are:

#define MAX_ACCELERATION_UNITS_PER_SQ_SECOND_X 1000 //was 1500
#define MAX_ACCELERATION_UNITS_PER_SQ_SECOND_Y 1000 //was 1500
#define MAX_ACCELERATION_UNITS_PER_SQ_SECOND_Z 100

/** \brief X, Y, Z max acceleration in mm/s^2 for travel moves. Overridden if EEPROM activated.*/
#define MAX_TRAVEL_ACCELERATION_UNITS_PER_SQ_SECOND_X 1000 //was 3000
#define MAX_TRAVEL_ACCELERATION_UNITS_PER_SQ_SECOND_Y 1000 //was 3000
#define MAX_TRAVEL_ACCELERATION_UNITS_PER_SQ_SECOND_Z 100

#define MAX_JERK 10.0 //was 20
#define MAX_ZJERK 0.3

about ready to switch firmware. I'm doing nothing fancy whatsoever so this setup should not be so buggy.

The firmware should have no effect on motor heating, you need to look a the current (Amps) setting of your drivers. setting this too high can also cause excessive vibration.

I have not measured the current during operation, but have turned the pots down to minimum.
I was careful to understand what that actually was and have tried turning current up and down.

I agree a real measurement is in order here, as that is independent like you say, no matter what the trim pot setting.

Thx for that suggestion.

thought I should mention how this was solved.
I bought stepstick drivers instead of the ones from sainsmart.
That solved things immediately.
I think the drivers were sending too much current, even though turned down on the trim pot.
Not sure though.

I have a fan on my electronics, not even heatsinks so far and no more issues.
I have read good things on the sainsmart parts, and the other items on my printer are from them.

But I did notice another post mentioning same issue with sainsmart drivers.