The manual transmission filler plug is located on the side of the unit. Be careful to identify the drain plug on the bottom and differentiate it from the filler plug on the side.
With the vehicle parked on a level surface and the wheels blocked, remove the filler plug. It may be necessary to raise and support the vehicle on jackstands if the plug is inaccesible when the vehicle is on the ground. If the fluid runs out of the hole, the level is okay and you can immediately reinstall the plug. If fluid does not run out, you can stick your finger into the hole to check the level. As long as its level is at or near the bottom of the hole (no more than about 1⁄4 inch (6mm) below) the level is ok. If necessary, add API GL-4 fluid with a viscosity of SAE 80W or SAE 75W–85W. You may want to purchase a syringe-like device for adding small quantities of such fluid from your local automotive parts store.