Would like to get some advice on how I might go about smoothing out a lawn that is extremely bumpy. Have a BX 25 and about 1.5 acres that I mow. The ground is blue clay. Was wondering if I  should get a box blade and start from there or go another route that I might not know of. Any suggestions welcome. 
One other  question,the manual says that 48" box blade is the max size. Right now I can get a good deal on a used 60" one. Is there a problem using the larger implement?
		
		
	 
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Greetings and salutations my neighbor to the north,
I would invest in a large quantity 
of gypsum and lawn lime pellets first,
as the gypsum will break up the clay 
quickly and the lawn lime will bring 
the PH back up and sweeten the soil. 
Renting an overseeder or finding a friend 
with flail mower with thatching blades will
also allow you to dethatch and in the 
process allow you to overseed the lawn 
with a broadcast spreader heavily and
water it lightly afterwards-the overseeder 
grooves hold the seed much better than
using straw or simply spreading and hoping
it germinates.  
Doing a soil test will scare (been there done that)
you and tell you you need a lot of gypsum and lime.
buying ton of lawn lime and a ton of gypsum 
(preferably the mined type) and not the chemically 
processed(quicker dissolving, no waste, easier to spread); 
Spreading a 1,000 pounds of each with a good spinner spreader 
at a slow speed will do wonders for the lawn(been there done that) 
the first time and the results will be quickly seen.
Spreading the other 1,000 pounds of each in the fall will help break up the clay even more and you will see the results in better turf if it is good grass.
The wide box blade will be and issue as you will have to make more passes at a very very shallow depth.   
leonz