Thanks for the answer!!
While the thrust lever is at the climb detent, are you sure that thrust output is constant. Do you by any chance remember how the gauges (N1, EGT, EPR - not sure which one you would use) change during the climb. Are they constant, increasing, decreasing?
The availabe power from the engines will decrease with increase in altitude (decrease in density), I am not sure if the A/C will try to compensate for this.
Happy new year!!!