Those ratings basically reflect the oil’s ability to function effectively given different driving conditions (read: pressure between meshing gear teeth). The most common ones you’ll see are GL-4 and GL-5. This is also where GL ratings come into play.
What’s good for one metal may adversely affect the other-so companies had to develop formulations that offered the requisite lubrication, yet wouldn’t harm any of the transmission’s components. The gears can be made of a hardened steel, while the transmission’s synchronizers (AKA syncros) are often made of a softer metal, like brass.
#BEST OIL FOR HARLEY TRANSMISSION MANUAL#
Manual transmissions are often made up of different metals. In other words, a 80w-90 gear oil is much “thicker” than a 5w-30 engine oil.īut viscosity is only part of the equation. Gear oil is different from engine oil.įor starters, gear oil can come in much higher viscosity ratings. Regardless of what your manual transmission uses, the fluid or oil’s primary function is lubrication-preventing metal-to-metal contact between the meshing gears. In fact, many modern manual transmissions actually spec for automatic transmission fluidinstead of a traditional gear oil. But gear lube isn’t the only choice for a manual transmission. Gear oil, AKA gear lube, is often used in your manual transmission’s gearbox, and you’ll commonly find it in older transfer and differential cases too. Keep in mind that most modern manual transmissions have gear oil service intervals well north of 50,000 miles, with many being “lifetime” oils.ĭriving enthusiasts, however, change gear oil to deliver improved transmission performance-like smoother shifting or added durability in extreme conditions. There are dozens of different types of gear oils, each with its own special designation and use, so we created this handy primer ( oil pun!) to help you make good decisions. Similar to what we discussed in our Automatic Transmission Fluid 101 post, selecting the right gear oil for your manual transmission isn’t as easy as it might seem. Selecting the right gear oil or transmission fluid is critical to the life and performance of your manual transmission.