...my 'base' 2009 Vibe with 1.8L 4-speed automatic and original P205/55R16 Goodyear "Eagle" tires (840 rev/mile) has the following calculated MPH-vs-RPM values:35mph @ 1,453 rpm45mph @ 1,869 rpm55mph @ 2,284 rpm65mph @ 2,699 rpm75mph @ 3,114 rpm85mph @ 3,529 rpm...however, the tachometer isn't graduated with the resolution needed to actually "read" those numbers; but, I can say that at 35 mph in 4th gear, the tach does indicate approximately 1.45K rpm...and, likewise, at 75 mph in 4th, the tach is showing approximately 3.11K rpm....it looks like the tire-diameter and gear/axle ratios (0.700:1 in 4th and 4.237:1 axle) yield 24.08 mph per each 1K engine rpm....also, I just had the speedometer tested today, and it has a constant offset of 2 mph (typical of most GM products with computer driven analog gauges):10mph actual indicates 12mph20mph actual indicates 22mph30mph actual indicates 32mph40mph actual indicates 42mph50mph actual indicates 52mph60mph actual indicates 62mph70mph actual indicates 72mph80mph actual indicates 82mph...and the place that did these tests also certifies and tests the Arizona Highway Patrol speedometers. She said most new GM speedos have the same 2-3mph offset...(computer reads wheel revolutions, calculates the MPH, adds "2", and sends the MPH+2 signal to the speedometer gauge)...assumed to be for differences in tire diameters, air-pressure values and loads....according to the Pontiac literature, the 2004 and 2009 transmission and axle ratios are the same, only the tire/wheel diameters are different: 2004 = 15" and 2009 = 16" (or 17" or 18")
...and the Devil said: "...yes, but it's a DRY heat!"
• 2014 Prius 1.8L eCVT
• 2009 Vibe 1.8L 4A
• 2004 Vibe 1.8L 4A