Played around in the past with various OD's in the .80- .70 range, results were often minimal for the effort, you really need to step into the .64-.50 range for the cost of adding an OD to "pay off"
Exactly. I have a Tremec 6-speed in a 2005 GTO, 400 hp, 3.90 rear, 25" dia tires.
Sixth gear 0.50:1 is super - runs about 1800 rpm at highway speeds.
But 5th gear 0.75:1 pretty much never gets used - it's a waste, not enough reduction. You really need the 0.50:1.
If you don't see two dolphins, you need a vacation.
