Hey Daniel. As far as motor oil, I would suggest going to AMSOIL's website and
www.bestsynthetic.com and looking at some of the comparisons. I'm going to be putting in AMSOIL my next oil change after doing a bunch of reading. It's pretty convincing.
John Fuddle said it was best to avoid synthetic tranny fluid. He said you don't want things TOO slippery in there since the clutches and all have to grab. In fact he said him and a lot of tranny guys he talks to are adding a 1/2 quart of gear oil to their fluid to give it some extra grab. They've apparently been doing it for a while with good results.
As far as the rear axle, that's already synthetic according to the owners manual.
As far as gains, one of the truck magazines did a full synthetic conversion on an older Chevy truck (motor oil, tranny fluid, and axles) and showed a gain of 10 hp on the dyno. I would think most of that would come from the motor oil change.
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