Many car owners neglect to check transmission fluids and gearbox oil levels, especially the gearbox oil for a manual transmission. The manual gearbox transmission housing holds the gears and shifting devices responsible for propelling the vehicle forward and backward. Manually shifting the car through the various gears allows a gradual increase in speed without taxing the engine. All gearboxes are filled with gear oil, which is a fluid much thicker than regular motor oil, indicated by a higher viscosity number. For the gears to properly mesh and rotate on their shafts, fresh gearbox oil should be checked and replaced according to manufacturer's maintenance intervals. Contaminated gear oil--or oil that has leaked from the housing, causing a low-level condition--can cause permanent failure of any part in the gearbox, even freezing up the transmission. Anyone can check the gear oil level with a few simple tools and a little precaution.
Park the vehicle on a level grade so the rear end and front end sit at the exact same height. A clean garage floor works best. If you must have the clearance to manoeuvre under the vehicle, use a floor jack to raise the vehicle. Place four jack stands under the frame members to the exact same notch or hole height on the jack stand support tube. This keeps the gearbox at the proper angle to get an accurate, level reading.
Move to the front of the vehicle and lay down on the floor. Find the gearbox and the filler cap on the vehicle. The manual gearbox on the 1996 Renault Megane sits under the front part of the engine near the bumper, located on the side of the transmission. Filler caps can be either plug-like bolts that require a 1/2-inch wrench to loosen them, or they come equipped with a plastic butterfly plug (you might have an aftermarket replacement). Use the 1/2-inch wrench end (without a socket) to loosen the bolt. Use a crescent wrench to unscrew the other variety. Both come equipped with small rubber ring gaskets; make sure not to lose it, or have a new replacement available.
Check to see if oil dribbles or pours from the refill hole after you have removed the filler cap. If fluid runs freely, it means the gearbox is topped off. Quickly put your thumb over the opening to prevent losing oil while you replace the fitting with the other hand. Do this with a fairly quick movement. Be sure to install the old gasket ring or a new one on the filler plug. Tighten to specifications.
Roll up a piece of paper into a tight tube and curl the end into a hook--this functions as a crude dipstick. Stick it inside the filler hole opening and curl it downward. Use this procedure if you do not see any fluid escaping the opening after removing the plug. Extract the paper tube and look for oil on the end of it. The level is too low if you see no trace of oil. Add oil accordingly.
If you need to replace gear oil, use a hand pump or a food syringe. Almost all repair facilities advise you to use your small finger to check inside the gearbox for any trace of fluid. You can use this technique, provided your finger actually fits into the filler hole. If it does not, use the paper dipstick method.
Be careful when hoisting the vehicle onto jack stands. Be sure they are placed squarely under the mainframe.