The Importance of Quality Oil Seals for Transmission Rebuilds

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The Importance of Quality Oil Seals for Transmission Rebuilds

May. 06, 2022

Rear Inner Wheel Hub Oil Seal for Isuzu Auto


Modern transmissions work hard, so shouldn't their oil seals do the same? Inferior seals are one of the most major diagnoses of transmission fluid leaks that can damage the unit beyond repair. When you're rebuilding transmissions every single day, it can be easy to forget how critical these small parts are, but in a system that operates under such high demands, the value well-made oil seals should never be underestimated. In today's post, we're here to discuss the importance of choosing quality when it comes to transmission oil seals.


Causes and Effects of Transmission Seal Leaks

A single transmission can contain dozens of sealing components, all with a specific purpose. If even one of those seals fails, the transmission in the vehicle can begin to leak transmission fluid. A transmission leak isn't simply an issue in itself, however; leaking seals can quickly lead to a multitude of other problems, including total transmission burn out.The purpose of an oil seal is to prevent lubricant leaks by closing in the spaces between a transmission's parts. The seals also prevent dirt and other contaminants from clogging up the unit. A static seal, such as a simple O-ring, fit between two stationary parts, while a more complex, dynamic seal has multiple lips and acts as a barrier between a stationary and a moving part.

Over time, due to varying pressures, stress, and heat inside a working transmission, seals will begin to break down — it's just a matter of time. However, depending on the quality of the seal, that time period can differ dramatically. Additionally, oil seals that accompany more active parts of the unit, such as the input and output shafts, experience a lot more wear and tear, and generally need to be replaced more frequently. And since several of these seals are located inside the transmission, they're tough to service without tearing apart the entire unit. Until a seal actually fails, it can be difficult to detect any sealing issues at all.

While proper maintenance and lubrication can aid in the longevity of an oil seal, seal performance is largely dependent upon the overall quality of the seal. Simply put, a poorly made oil seal cannot withstand the pressure fluctuations inside a modern transmission, and will cause more transmission leaks and issues in the long run. Therefore, it's important to choose the highest quality oil seals when rebuilding transmissions in your shop.


Quality Seals Under Pressure

To find oil seals you can truly depend on to hold up long after the rebuild is finished, there are a few key markers of quality you should be looking for. The material a seal is made out of is one huge indicator of quality. Cheap rubber seals don't have the same durability as more innovative materials like polyacrylate, ethylene acrylic, hydrogenated nitrile, fluoroelastomers, and more. Each of these materials has different properties that determine how they perform in different temperatures and environments.

Another true indicator of oil seal quality is its inclusion in the original unit as an OE component. OE seals for rebuilding are the exact same seals used by the original transmission manufacturer to build the transmission, so you can be confident that OE seals will have the highest level of performance as well as the best fit inside the unit.

While no oil seal can last forever, the quality of the seals you choose to install in your rebuilds affects not only the success of that job in the shop, but also the value of your work over time. Using well-made, high quality seals that are able to withstand the high demands of today's transmissions will only increase your productivity in the long-term.


Crankshaft Rear Wheel Oil Seal for Mitsubishi


7 Important Factors to Consider When Choosing Oil Seals

With varieties of seals available, choosing the right seal for application can be a daunting task. The following factors will help make the right selection.

ㆍLubricant: If choosing lubricated seals ensure they are continuously lubricated with oil that possesses appropriate viscosity required for the application and the lubricant is compatible with the elastomer material of seals.

ㆍShaft Finishing: A good surface finishing of shafts gives a very effective oil sealing. The ground or polished shafts with concentric finish marks provide the best sealing that prevents leakage even during the shaft rotations. Hence, it is important to make sure that the shaft finishing is well maintained.

ㆍShaft and Bore Tolerance: The seals must be strong enough to tolerate the pressure and vibrations caused by shaft and bores. The authenticity of metal and elastomer material is something that makes the shaft and bore tolerance possible. Therefore, check if the material meets these requirements before buying the seal.

ㆍShaft Hardness: The life expectancy of a seal is measured on the basis of the hardness of its shaft. A shaft must possess a Rockwell hardness of 30 or above. When a seal is exposed to abrasive contaminants or high pressure, this RC hardness protects the seal from getting damaged. Hence, it is an essential factor.

ㆍTemperature: The temperature of the process should not exceed the temperature of the seal elastomer. Any increase or decrease in temperature may affect the sealing capability of the seal. Hence, it is an important point to be considered.

ㆍPressure: Most seals are designed for applications where they may be subjected to pressures as low as 8 psi. However, if they are subjected to even low pressures then pressure relief must be ensured.

ㆍShaft Speed: Shaft speed depends on many factors including shaft finish, its concentricity, the type of liquid being transferred, and the type of oil seal material. So each of these factors must be considered to achieve a maximum shaft speed.


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