help wit tko 500

[almostthere4v]

ok my 3650 went out last year, i had some extra money so i replaced it wit the tko 500, well i was doing good with it and then one day 2nd started to grind while racing. i thiught it was my fault so i didnt think much, well the next time i know i held the clutch down and it still did it, well i took it back to the ford dealership where i got bought it (they got it fromm D&D) and told them it grinds at 6800 rpm... well they said that the tranny was not ment for over 5800 and thats what i have to shift at... well i dont know why they put a 5800 rpm in a 6800 rpm car.. but now the syncro are messed up cuz =of the lack of info that was relayed.... i'm pissed..
so how come i have to shift at 5800 and how can i change it?
and why is the a notch before you get it in gear? it throws me off.
thanks