I would agree with blackfarmer2's post above.

I have a 2003 model 1770NT with the Maxemerge Plus units.  I would never, ever buy another one with the stamped steel units and would exclusively look for XP's or newer with the cast units.  I continuously fight cracks in the units and the opener bearing life is terrible in no till.   I actually keep two sets of openers around and swap mid-season before the bearings go out.  I have some blades that I have replaced bearings in 3 times and the blades still measure 14.75".  Major source of frustration and downtime.

When the bearings go out, wet soil starts to build up between the disks and wedge them apart.  If you don't see it and stop immediately it will actually pull the threads off the center spindle.  The spindle is considered to be non-replaceable.  Deere's solution is to sell you a new shank.

The XP/cast units run a double-roller bearing that looks much more robust.