A mechanic at Ford told me that the blocker plates were made from a carbon fiber base + other materials. Some fluids cause these plates to swell which equals the harder shifting. I do not know of all of the good or acceptable replacemnet fluids that are on the market for out transmissions, but he told me that GM syn. is one of the best. Of course it is used in the ZO6's and is the same fluid useed in the Vipers. JMO
No, GM Synchromesh is NOT used in the Vipers. oke:
I own an 05 and the trans comes stock with Castrol Syntorq.
GM Synchromesh did however make my T56 in my Cobra shift like butter.