On Tue, 22 Sep 2009 10:22:26 -0700 (PDT), David Johansen
wrote:

This summer we laid sod in our backyard and we prepped/flattened the
sod underneath,

Not sure what you mean by "sod underneath", did you really lay new sod
over old sod? I'd like to hear you laid new sod atop freshly prepared
earth.

but we were in a rush to try and finish some things up
before it started raining and I guess we walked on it too much before
it all settled because now the ground is fairly uneven and not as flat/
level as I would like.

Is there a way to level the ground under the grass now that it's
established?



You don't want to level the grass, you want to level the ground the
sod/grass is set on. One of the best ways (and should have been done
prior to laying new sod) is by running a roller back and forth and
crosswise. You can still roll the area to help level the ground, just
don't use too much weight lest you damage your new sod... fill the
roller only about 1/3 with water. You don't say how much area but it
would be best to use a a push roller, but if your area is large you
may need to tow the roller, than use the lightest weght tractor with
the widest wheels. In any case you'd do best to apply light pressure
and repeat the process like every two days rather than attempt to roll
it smooth all in one go. With sod lawns you would do well to roll
twice every year (spring and fall). I always suggest a seeded lawn,
seeded lawns are far healthier and more enduring, sod never actually
roots into the ground... sod is more like a hair piece than you may
think.