Alternative Ways of Opening a Square Drain Plug

In modern vehicles, the transmission drain plug features a hexagonal head or a star-shaped recess. You can open and close a hexagonal plug with a socket wrench, while you need a Torx bit for a star-shaped drive. But what if you own an older truck with a square-shaped drain plug? It requires a square plug socket, and not everyone keeps such a specialized tool in their toolbox. So, is it possible to remove a square drain plug when you don’t have a square plug socket?

No Square Plug Socket? No Problem

There are alternative ways to open and close a square-headed transmission drain plug if you lack a square plug socket. Take a look at the following approaches:

Use an Open-Ended Wrench

Your toolbox usually contains several open-ended wrenches. Also called open wrenches, their profiles–the space between their heads–fit around fasteners.

Start with an open-ended wrench with a profile that is the same size as the square-shaped transmission drain plug. For example, use a ⅝-inch wrench if the fastener also measures ⅝ inches.

Does the open wrench feel loose around the square drain plug? Don’t force the issue. Instead, look for another wrench that’s one size smaller.

The head of the old drain plug might have decreased in size because of accumulated wear. After many years of repeated removal and installation with tools slowly but surely grinding away at the metal, the fastener’s head is probably smaller than a factory-fresh part.

Use a Long Open-Ended Wrench

Sometimes, the open-ended wrench snugly fits over the drain plug’s square head, but the plug might refuse to budge no matter how much you move the wrench. You’ll need more leverage to break the tight seal without applying an excessive amount of force that might damage the drain plug.

The other end of the wrench will usually have a 12-point closed end. Try using that for a better grip on the square head.

Alternatively, check your toolbox for another open-ended wrench with the right profile and, more importantly, an extended handle that increases leverage. Use the wrench with a long handle to unfasten the drain plug.

If none of the open wrenches in your collection meet your criterion, you can try extending the handle of the tool that does fit over the drain plug. Slip a pipe or a jack handle over the open-ended wrench to increase its handle’s length.

Try a 12-Point Socket

Did the square drain plug remain in place despite using an open-ended wrench with an extended handle? Or were you unable to either find a wrench with a longer handle, increase the handle’s length, or fit the tool in the workspace?

One of the 12-point sockets in your toolbox might fit the four-point (square) drain plug. These tools follow the metric system of measurement, so you must convert millimeters into inches to determine which sockets can accommodate the plug.

Furthermore, some 12-point sockets might not fit the drain plug despite having the same measurement. If that happens, try using the socket that’s one size up or down to compensate for any discrepancies in the conversion.

Exert care when you test the compatibility of each 12-point socket with the square drain plug. If you force the fit and loosen the plug too forcefully, you might strip the plug’s thread. It’s important to observe the drain plug while you work the socket.

Use a Ratchet

In some vehicles, the drain plug is in a cramped location that’s difficult to reach. You cannot fit a wrench in there, especially if the tool has a long handle.

Instead of trying to fit a wrench in such tight areas, use a ratchet. The latter can apply comparable levels of force to a fastener without taking up as much space as a wrench. Using a socket and ratchet is highly recommended because they have the least chance of rounding the drain plug.

Using a socket and ratchet is actually the best method to open a square drain plug because this has the least chance of rounding the drain plug.

–Anthony Harlin, ASE Certified Master Automobile Technician

Get a Square Plug Socket

In the worst-case scenario, none of those alternatives worked. Alternatively, you might have gotten cold feet over the risk of accidentally stripping the square drain plug.

If all else fails, search and shop for a square plug socket online. Keep in mind that these sockets are more costly than hexagonal or 12-point sockets because of their rarity and specialty.

Tips For Working on Transmission Fluid Pans With Square Drain Plugs

Opening a square drain plug is only one of the many steps in changing your vehicle’s transmission fluid. The following tips can make your life easier whenever you work with transmission fluid pans:

Loosen the Fill Plug

In addition to the drain plug, many transmissions have a fill plug that covers the opening through which you can add new transmission fluid. A stuck fill plug will prevent you from topping off your vehicle. If you drain the transmission fluid before realizing that the fill plug isn’t loosening up, you’ll end up with a dry transmission that isn’t safe to drive. Thus, check the fill plug as well as the drain plug before you drain the transmission.

Use the Correct Transmission Fluid

Aside from square drain plugs, older vehicles might use an earlier type of transmission fluid. Using the wrong transmission fluid might damage your car, leading to costly repairs.

Find out the manufacturer-recommended formula for your vehicle’s transmission. Your owner’s manual usually contains that information. Once you’ve identified the formula, look for it.

If you cannot find the original transmission fluid, look for a modern formula that’s compatible with your vehicle. Ask an expert if your car or truck can accept the new fluid. Follow this tip for other vehicle systems that use lubricant or fluid, such as the differential and transfer case.

Warm Up the Transmission

In many vehicle models, you can make the transmission fluid change easier by warming up the transmission by starting your vehicle and either letting it idle or driving it for a short period. Warmer fluid flows smoother, allowing you to drain the transmission faster.

If you don’t want to accidentally burn yourself while draining the transmission, you can skip the warming-up process. However, there’s a higher chance that old fluid and residue might remain in the transmission after draining. You can compensate for this by draining the transmission on a warm day.

This approach isn’t recommended for every vehicle model. Some BMWs need you to fill the transmission in a specific way, monitor the temperature with a scan tool, and return the fill plug once the temperature reaches a certain point. It’s recommended to check the manufacturer recommendations for your vehicle to see if you can warm its transmission before changing its transmission fluid.

Look For Debris in the Draining Transmission Fluid

Keep an eye on the transmission fluid as it drains from the transmission of your vehicle. You might see pieces of metal debris in the fluid.

If you spot small numbers of relatively minuscule metal in the transmission fluid, they might be the product of hard shifting between gears.

A significant amount of debris indicates severe issues with the transmission. The same can be said if you see large pieces of metal. Consult a trusted mechanic as soon as possible.

Use a Squeeze Bottle or Hand Pump

Does your vehicle lack a dipstick? There are two ways to refill a transmission that doesn’t have a dipstic. The first approach is to use a dedicated hand pump. The second way is to fill a squeeze bottle with fresh fluid and squirt it inside the transmission.

Find a Compatible Oil Drain Plug For Your Car

Are you planning to modernize the old-fashioned square oil drain plug in your vehicle? You must choose a drain plug that fits the transmission’s drain hole. Fortunately, you can easily find a compatible oil drain plug here at CarParts.com.

CarParts.com carries a wide array of high-quality oil drain plugs and other replacement parts. Finding the right product in our extensive catalog is a breeze. Enter the year, make, model, and engine of your car or truck in our vehicle selector, and check out the results for an item that fits your budget and machine. We exclusively source our oil drain plugs from trusted brands, ensuring you get an oil drain plug that works and lasts. If you have any questions about our products, our customer service team is available 24/7 to assist.

Looking for a high-quality oil drain plug? Check out CarParts.com. Choose from our selection of oil drain plugs and get them in a few business days when you order today!