SM465 Oil Type - Yes it Makes a Diffference

[cleszkie]

Just wanted to share my experience with using different types of gear oil in my SM465.

Got my SM465 professionally rebuilt by very reputable shop (Anaheim Gear in SoCal) about a year ago. They did all the little tricks to improve the detents, and to improve shifting. I installed it and filled it with 80W-90 Hypoid gear oil with GL4 and GL5 rating (before I recently learned that oils with GL5 rating are mildly corrosive to yellow metals such as the brass synchros in the SM465). The tranny shifted great for the past year until it recently began acting like the synchros were not working properly. Shifting was getting harder and it was wanting to grind during shifts at times. Long story short, I drained the old oil out, removed top cover and side inspection cover to take a look at the synchros. The oil looked good (a little dirty but no brass dust, shavings, or chunks), and the synchros looked good. I had to look long and hard, but finally found a 85W-90 gear oil that was only rated GL 4. It actually stated on the side of the bottle that it was not corrosive to brass! Filled the tranny with this oil and my shifting issues immediately went away. It now shifts much smoother, like when it was just rebuilt. This is just my personal experience, but it seems to support the fact that this tranny is intended for GL 4 rated oil, and that GL 5 rated oils can cause problems. Hope this helps someone out.