Adding too many clothes to your washing machine can stress the motor or transmission, causing them to overheat or malfunction and emit a burning smell. For top load washers, overloading can cause the agitator to freeze or malfunction, stressing the drive belt and causing friction, which could emit a burning rubber smell.
Tilt the washer back and remove the belt, replace if slick. Check the tranny and motor pulley's for burnt marks, then check the pump for bad bearings. Post results.