Folks, he's talking about a MANUAL transmission, the 5-speed. There is no "overdrive" button on the manual. 5th gear is an overdrive gear, by definition it is a gear that has the output rotating faster than the input, and the .811:1 5th gear is just that.

The 5-speed is the FS5R30A, which is apparently a variant of a Borg-Warner T5. It has been used in the truck/SUV line for quite a while, and was also used in the 87-89 300ZX Turbo, some Patrols, and some Skylines. The earlier 300ZX and 280ZX used an actual T5. The T5 has been used in all sorts of vehicles over the years and it may be possible to swap out some components from a T5 or another FS5R30A application to get a taller 5th gear, but I really don't see the point. It would be a lot easier and probably cheaper to just change your diff gears out with some 4.3 gears from a wrecked Pathfinder if you want lower RPMs, but that wouldn't change your tach/speedo correlation, you would just read a higher speed than you're actually travelling.

Brent