Mine will do 71mph, with the Allison and 4.78 gears. I dont think it's getting too many rpm's yet either. For some reason my gov springs were set to 2850rpm at the factory. Most older ones seem lucky to hit 2700, from what I've seen. Just the simple 2 clicks should get it up another 2-400 rpm, not bad for free. Otherwise it's a call to Scheids for new springs, I haven't yet called them to see if the 12V Cummins gov springs are the same. I've done the 2 click method in a few trucks (DT466's and a Ford 7.8)and they all had the allison, but WOW! what a difference in those! On a manual it'll help overlap the gears a little more. Duke, you can get different gears in the rear now that it has the power to push it.