#Gear oil weight chart Patch

Just 9-years after the end of 9-inch production, in 1995, both the GL-6 standard and the test equipment were inactivated, making it unlikely that a synthetic oil manufacturer would go through the cost and effort to develop an oil to meet the obsolete GL-6 standard.īecause many of today's commercially available synthetics are not engineered with the 9-inch's requirements in mind, Currie advises using only conventional 85W-140 non-synthetic GL-6 rated gear oil in all front and rearend applications. The last 9-inch rearend rolled off the Ford assembly line in 1986, and it wasn't until 3-years later 1989 that the first synthetic gear oil, Mobile1 (GL-5 rated), hit the market. Virtually all synthetic gear oils on the market today are only engineered to meet the API GL-5 specification, which Currie has found to be inadequate for the design of the 9-inch. The increased pressure capabilities and wear resistance found in Currie’s GL-6 rated gear oils are designed with all this in mind to ensure your rearend’s gears and bearings are adequately protected under the most severe conditions. Because of this, not using high-shear oil such as Currie’s 85/140w can lead to scoring and certain gear death, especially during extreme scenarios such as off-roading and racing. However, strength comes at a price, as this high-offset distance creates increased sliding friction and heat across the gear tooth face.

#Gear oil weight chart Patch

The high-offset distance increases the contact patch between the ring and pinion teeth by approximately 30-percent and is a crucial reason for the legendary strength of the 9-inch gears. The design of the 9-inch features a high-offset distance that places the center-line of the pinion gear 2.25-inches below the center-line of the ring gear, which is substantial when compared to the 1.125 to 1.5-inch offsets of other gear sets (see image below). You may hear about how synthetic gear oil provides reduced friction and wear however, it may not be optimal for your setup – especially if you have a Ford 9-inch rearend. In the worm gears the temperature may reach 200☏ (93☌).We get asked this question almost every day, and the answer is straight up, you should only run 85W-140, API GL-6 rated conventional (non-synthetic) gear oil in a Currie axle assembly.

The highest operation temperature in spur gears is about 130☏ (54☌). Pour point of syntethic oils may reach -50☏ (-46☌). Mineral oils possess relatively high pour point - about 20☏ (-7☌). The low temperature limit of a gear oil is 9☏ (5☌) higher than its pour point (the lowest temperature, at which the oil may flow).

Viscosity of a gear oil depends on the temperature, therefore an oil selected for a particular gear should provide its reliable operation within the expected temperature range. High viscosity provides thick oil film, high wear resistance and low galling even at high pressure (EP). High viscosity is favorable for: low speed, highly loaded gears with a rough tooth surface. Low viscosity provides thin oil film, low friction (high mechanical efficiency), good cooling (heat removal) conditions. Low viscosity is favorable for: high speed, low loaded gears with a good tooth surface finish. Viscosity of gear oils (lubricants) is a compromise between the gear parameters requiring low viscosity and those requiring high viscosity.