gear oil

Just saw. This thread. I only use GL6 oil in my trans and diffs. 75/140 for the diff and 75/90 for the gear box. While the test is obsolete the oil is not. The real issue is that the GL6 test was a mother bear to pass so when the need dropped off, most oil companies just went to the GL5 rating.

A quality GL6 oil only has one issue and it's not brass. Because brass has a sticky feel to it, and because the factories wanted to cut back on how many lubricants they had to buy and store, they started using linings on and different materials for the syncros. An example would be an early 90's crapstain (mustang for the short bus and dorf guys) that had, iirc a wet clutch lining on the syncros. Or a Dodge Daytona of about that same era. Same thing. The GL6 oil is "slick" enough that the syncro can't grab the gear and slow it down. Now you have grinding. Don't ask me how I know this.

It's 2016 and I can't imagine anyone NOT running a synthetic oil anywhere you can. I have done the testing and a QUALITY synthetic oil always makes more HP and lasts longer and runs with cooler than any dino oil. Just a plain fact.


BTW, do we really care what they were doing in 1970? Do we run that era camshaft? Piston? Tires? Heads? No most of us wouldn't. I know there are some guys who still live in the past but that is just stubbornness or fear.we should be ruled by neither.