Over the Past few months I have seen a number of gearboxes coming to me with damaged Synchro rings and Hubs all using a common oil, that the customer thought was the best stuff to use for their application.
The Redline brand of oils are excellent, but the issue is people using the wrong type of oil for their application.
Redline Shock proof oils should only be used in final drives and dog boxes only! as it has friction modifiers that do not work well with synchromesh gear boxes.
If you are going to use Redline oil in your Synchromesh gear box, please use only MT-90 75W90 GL-4 Gear Oil.