Reply to "changing fifth gear to a taller ratio"

The 215/70VR15 tires that were oem on Panteras were 26.8" diameter. The H60 tires on the Ford spec Pantera L were 27" diameter. The 285/50VR15 Pirelli P7s on the Euro GTS Panteras were 26.2" diameter. All these Panteras had the 4.22:1 gearing as standard equipment.

The GT4, GT5 and GT5-S Panteras had 345/35VR15 Pirelli P7s which were only 24.5" diameter, that is why those cars were equipped with taller gears, most often 3.77:1 or 4.00:1.

Installing a ring and pinion with a higher gear ratio (smaller numerically) has the effect of giving the car a wider ratio gear box, you may like that, you may not. It would depend upon how you drive your car. The standard 5th gear in most Panteras is 0.846:1. Here's the overall 5th gear ratio for the 4.22:1 ring and pinion, and the available higher ratio ring and pinions:

4.22 x 0.846 = 3.57:1 (standard)
4.11 x 0.846 = 3.47:1
4.00 x 0.846 = 3.38:1
3.77 x 0.846 = 3.18:1
3.56 x 0.846 = 3.01:1
3.44 x 0.846 = 2.91:1
3.20 x 0.846 = 2.70:1

An over drive 5th gear is much less expensive than a new ring and pinion however, it allows the gear spacing to remain the same while providing a more relaxed crusing gear, and a higher attainable top speed. Here's how the available higher 5th gear ratios affect the overall 5th gear ratio with the standard ring and pinion:

4.22 x 0.846 = 3.57:1 (standard)
4.22 x 0.740 = 3.12:1 (about the same as using a 3.77 ring and pinion)
4.22 x 0.704 = 2.97:1
4.22 x 0.655 = 2.76:1
4.22 x 0.642 = 2.70:1 (same as using the highest ratio ring and pinion available)
4.22 x 0.620 = 2.61:1

Changing the 5th gear is the economical way to achieve a more relaxed cruise rpm. I've never known anybody to regret installing the overdrive 5th.

-G