Transmission fluid is an oily, slimy substance that keeps the gearbox well lubricated. The liquid you need depends on the model of your car and the type of transmission: manual or automatic. Consult your vehicle's user and maintenance manual and follow the instructions to check and top up gear oil. The suggestions in this article apply to the most common checking and refilling procedures.
Steps
Part 1 of 2: Check the Liquid
Step 1. Start the engine
To correctly assess the oil level, you must read it after running the engine for a while and when the fluid is hot. Take the car to a parking lot, apply the handbrake and proceed to the check. Remember that for some models it is necessary to put the gearbox in neutral. Always check the instructions in your car's manual to know which report to insert.
- If the machine has been off for at least half an hour, you should start the engine at idle for a few minutes before continuing with these operations; in this way it brings the oil temperature to normal operating conditions.
- Some cars are equipped with a stick probe with a graduated scale for "cold" readings. Despite this, you should still run the engine for a few minutes to warm up the oil and get an accurate measurement.
Step 2. Press the brake and move the shift lever in all gears, but do not drive the car
Don't neglect reverse and overdrive, if any. If you check the transmission fluid cold (i.e. without having driven the car and not having entered all the gear ratios), the inspection using the rod probe could lead to incorrect values. In this case, you may think you have more liquid than you think. To avoid this mistake, move the shift lever in all gears to allow the oil to flow evenly.
Step 3. Open the hood of the car while it is parked on a level surface and locate the transmission probe
For some models, it is easy to confuse this probe with the oil pan probe, so make sure you have located the correct component.
- Look at the rear of the engine compartment, near the firewall. In rear-wheel drive cars, this is usually found here.
- Front-wheel drive cars mount the transmission fluid probe in the front of the engine compartment, where it is connected to the drive shaft.
Step 4. Take out the probe and clean it with a rag
This way you can have a precise value.
Step 5. Put the stick back into its slot and take it out once more
At this point you should be able to see the level reached by the transmission oil. Remember to refer to the "hot" scale of the probe.
Part 2 of 2: Top up the Liquid
Step 1. Start the engine at idle while the transmission is in neutral and the handbrake is activated
The engine should be running when you top up the transmission oil, so you must leave the transmission in neutral and the parking brake on for safety.
Step 2. Read your car's maintenance manual to understand how to properly top up the fluid
By doing this you will know which oil to use and if there are any special precautions you need to take.
- Sometimes, the name of the type of liquid to be used is stamped on the stick probe. Remember that there are many kinds of fluids, each with specific characteristics that make it more or less suitable for engine transmission.
- Also check how often you should change the oil. Although it can be refilled when the level drops below the minimum, many car manufacturers recommend changing it every 48,000 or 161,000 km, depending on the model.
Step 3. Insert a funnel into the transmission probe hole
You need a funnel with a rather long spout, to avoid overfilling the tank.
Step 4. Slowly pour the correct amount of fluid into the transmission
Add it a little at a time to prevent it from overflowing. The amount to top up depends on several factors:
- If you are doing a simple top up because there is little oil, start with 0.5-1 L of liquid. Check the level again and continue adding 250ml at a time until the liquid reaches the "maximum" mark.
- If you are performing maintenance, disassembling the pan and replacing the filter, then you will need at least 4-5 liters of oil to replace what you have drained from the pan.
- If you have decided to change the transmission fluid completely, then you may need 9-13 liters of fluid to replace all the old one.
Step 5. While the engine idles, depress the brake pedal and move the shift lever to all positions
This operation allows the oil to flow and allows for correct measurements.
Step 6. Check the oil level once more
You probably won't need to add more, but if you need to, you need to proceed gradually rather than pouring in a lot at once. Remember that most vehicles don't need more than 500ml of fluid.
Step 7. Put the probe back into its housing and make sure it fits snugly
You will likely need to rotate or press down on the latch on the top of the stick; by doing so you are sure that you have locked the probe in its seat.
Advice
- Ask the mechanic to check the transmission fluid every time you bring the car to him. If you don't know how to top up it, ask the mechanic to do it for you.
- Some cars do not have a stick probe to check the oil level and top up. Car manufacturers call this type of transmission "tamper evident". This way only authorized workshops or dealers can check and add fluid during major service. In some cases the liquid does not need to be replaced at all. Always follow the manufacturer's instructions.
Warnings
- Consider having your car's transmission checked by a mechanic in case you need to constantly top up, as there could be a leak.
- Be careful not to spill the wrong fluid in the transmission. Otherwise you will damage the car and the repair may not be under warranty.
