* Specific Mack Model: Mack trucks in 1980 came in various models with different engines and transmissions. Each combination will have a different optimal shifting strategy.
* Transmission Type: The number of gears and gear ratios will dramatically affect the ideal RPM for shifting. A ten-speed will shift differently than a five-speed.
* Engine RPM Range: The engine's power band will determine the most efficient RPM range to operate in.
* Load: A heavier load will require shifting at lower RPMs to avoid lugging the engine.
* Terrain: Steeper grades will require lower RPMs and more frequent shifting.
While 2000 RPM might be *around* the shift point for some gears in some 1980 Mack trucks under specific conditions, it's not a universally applicable number. The driver's manual for the *specific* 1980 Mack truck model is the only reliable source for proper shifting guidelines.
