I have noticed that the 4L80E was put behind everything from the V6 to the Duramax. We all know how well it stands up to powerful smallblocks. How does it stand up behind the Duramax? As far as I know the Allison only came behind the 8.1L and the Duramax. It has to be beefed up when a Duramax is modified. How does it stand up behind a modified big block? What kind of mileage does the 8.1L get with the Allison?