Has anyone had their 6th gear unlocked on an allison md3060 transmission? I have a 2003 Bluebird All American RE 8.3 Cummins with the md3060 - but only has 5 speeds available. RPMs are about 2150 at 70mph - I'm told with 6th gear unlocked, it would drop RPMs to around 1800 - and on long hauls, that would mean significant $aving$. If anyone has any advice, please share. Thanks!