you can till the sod, but you have to do it in multiple steps, each one with a lower tiller setting. after each pass with the tiller, you need to take a gravel rake and rake the loose sod out of the patch (shake it off if you need the soil), and put it in your compost as it makes amazing compost and helps a slower pile pick up the breakdown pace. you cannot till and till until the sod is gone as each little root cluster will grow back into an annoying weed. if your back is really bad, this might be the best option but it does take a little longer to complete. if your raised beds are high enough, the added topsoil and compost will suppress most of whatever gets left in your patch. my wife and i started our garden this way and had the same if not less weeds than my brother in laws garden that was cut sod and hand double-dug.

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1985 300D - 1984 Euro 280E AMG Clone (SOLD) - 1978 280CE (SOLD) - 1983 300D (SOLD) - 1981 300D (SOLD)