Hello,
Have a dcc sd40-2 and discovered a common problem fix for having to turn the throttle up half way to get it to move .Discovered this when IT RAN IN ONLY 1 DIRECTION ON DC.
THE WIRES WERE FRAYED down to the last thread at the motor re soldered AND IT RAN , BUT WITH NO ACCELERATION IMPROVEMENT ALONG WITH THE COMMON MOTOR BUZZ.
To fix this I REPLACED THE MOTOR WIRES WITH A BIT LARGER GAUGE and walla the common buzz was gone!set cv 2 to about 100 and it will run tie to tie notch 2 , Instead of half throttle just to get moving, BUT this engine has flywheels and factory DCC ON BOARD.
jACK