If you've ever noticed that your gearshift feels "notchy" or gets excessively hot, it's probably time to lubricate your gearbox. The Miata is rear-wheel drive car, so the gearshift sits directly above the transmission, making the job fairly simple. You should inspect the gearbox turret oil annually, and replace it if it is dirty or low. It's also a good idea to inspect or replace your upper boot cover when servicing the gearbox.
Remove the center console. Unscrew your gear shift knob, remove the screws in the storage compartment, remove the two screws on the side of the console, then remove the screw in the cup holder. Lift the console forward and up; disconnect the electrical connection and set it aside.
Remove the gear insulation and remove the four bolts mounting the upper boot cover. Pull the upper boot over the gear shift lever. Once the upper boot cover is removed, you'll have access to the three bolts mounting the gearshift. Remove these bolts and pull the gearshift from the exposed transmission.
Remove the old oil from the turret. If you've never serviced the gearbox before, it's likely you will have little to no oil. Use a baster to suck out the old oil. You can also use a syringe or a baby's "nose sucker." Whatever you use, delegate it to your toolbox afterward. Do not reuse it for anything but automotive applications; it's nearly impossible to properly clean and sanitize.
Fill the turret with approximately three ounces of gearbox oil (about halfway full). Replace the shift lever and tighten the bolts, and then replace the upper boot cover and tighten the bolts. Put the insulation back in place.
Reinstall the center console. Tighten the screws mounting the center console and replace the gearshift knob. Move your gearshift around a bit. It should feel less "notchy" and more fluid.
