Reference: Manual Transmission Oil

[Wayne Hingley]

Some recent posts on transmission lubricants in Jordan's C15A thread http://www.mapleleafup.net/forums/sh...t=3643&page=13 caught my attention. Specifically the posts of Rob, Robert and Lynn (in around post #371), related to oil compatibility with brass (soft yellow metal) components.

From some training on oils and lubricants that I had about 8 years ago, I specifically remembered that soft yellow metals can be severely damaged by certain oil additives. Certain extreme pressure (EP) additives are not compatible with these soft yellow metals, and knowing this along with seeing the posts mentioned above, I was immediately alarmed. In recent years, EP has become a common additive to many of the newer gear oils for modern vehicles, as the EP additive is used to cushion the contact surfaces of gears to reduce wear, and give a smooth feel when shifting and engaging. Im assuming that modern manual transmissions do not have brass components, so the use of EP has become very standard, other than some exceptions such as mentioned by Rob with his Dodge transmission.

The Dana/Spicer jeep transmissions do have several brass components, and the use of common EP oils will have a negative effect as mentioned by Robert and Lynn.

Below are a couple of slides about EP additives from my training package.