In A Fix: 3 Fluids Your Gear Oil Should Never Resemble

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Your car's manufacturer designed the manual gearbox with a series of moving parts, such as ring gears and bearings. These moving parts rely on the fluid, or gear oil, in the reservoir for all of their protection, lubrication and cooling needs. To keep this protective substance in good shape, your car must receive regular fluid changes every 30,000 to 60,000 miles, depending on the make and model you drive. Furthermore, your transmission must have adequate seals that keep water out of the case at all times. If you suspect any problems, it pays to quickly check the fluid consistency by sticking your finger in the cold fill hole on the side of the transmission. If you come back with fluid that looks like any of the following substances, rather than black, viscous fluid, get your car to a transmission repair shop immediately.

Mud

If you neglect to have your gear oil changed at the mileage recommended by the manufacturer, the lubricants will start to break down at a rapid pace. Eventually, your gearbox will be packed with a mud-like substance that cannot flow between the moving parts. As the thick, useless gear oil sits in the bottom of the transmission pan, the moving parts above will start to wear away at a rapid pace.

The increased friction will also cause the parts to heat up to unsafe temperatures, possibly leading to severe breakage. The second you find exceptionally thick gear oil in your transmission pan, have your car towed to the shop in an effort to minimize damage as much as possible.  

Chocolate Milk

In addition to the cooling properties of gear oil flowing between moving parts, manual gearboxes often have coolant lines running through their system. If the coolant lines spring a leak, they may send a watery substance flowing into the pan below. As the water dilutes the gear oil, it turns into a substance that looks just like chocolate milk.

In fact, as the transmission components rotate around in the case, it whips up this mixture to create the telltale bubbles found in a glass of milk. Unfortunately, this mix of fluids will quickly cause extensive damage, such as corrosion, to your internal transmission components. To solve this problem, technicians will need to flush out the system until every last drop of water is eradicated.

Blood

If you spot a thin, red substance on your finger during the fluid check, stay calm. Your car is not hemorrhaging out. Unfortunately, the reality is nearly as dire. Red fluid in your manual gearbox can only mean one thing: it was filled with automatic transmission fluid instead of gear oil. Automatic fluid does not have the viscosity, lubricant and heat absorption properties needed to support the manual transmission components. Without the proper oil weight, the gear surfaces could rub directly together, chewing off sections of the teeth over time.  

Getting The Fix

Your transmission expert will assess the situation and start a gearbox flush right away. Depending on the severity of the fluid problem, your vehicle may need more than one flush to remove all of the fluid residue. Removing all of the worn out, contaminated or incorrect fluid will give your transmission a fighting chance.

Brace yourself for the worst, however, if you have been driving the vehicle with the defunct fluid for any length of time. Without fresh, effective gear oil, it is highly likely that the moving parts developed worn areas much faster than normal. Thankfully, if the damage is severe, you can always have your transmission rebuilt to make it function like new. After making the necessary repairs, your technician will fill up the gearbox with the appropriate gear oil weight, as listed by the vehicle manufacturer, before sending you on your way. 

For more information, contact a local transmission repair shop. 

29 January 2015