The first direct drive designs from 1981-1984 did not have neutral drain. They started to change to neutral drain in 1985 with all models after 1986 having the neutral drain. The neutral drain models are all pretty much the same with some minor internal design modifications over the years. There may be a couple models with different length agitator shafts. You cannot add neutral drain to the non-neutral drain models. I assume, if the mounting alignment was the same, you could put a neutral drain model in an old non-neutral drain washer but it would never spin unless you could change the timer out as well. The motor must pause after draining to disengage the neutral drain.

Eric

You can just do a search on appliance date codes, but basically for Whirlpool, for date of manufacture since 1990, the second or third letter of the serial number indicates the year and the first two numbers indicate the week. For 1990, the letter is X and for 1991 it's A. Since then, some letters are not used (I,N,O,Q,V,Z). You can also determine the date a washer was introduced from the third from last character in the model number. It is somewhat different than the serial number code. An X here would be either 1991 or 2010. Unused letters are C,I,N,O,Q,U,Z. I don't know how you would tell the capacity of a washer without the original documentation from sale without measuring the tub and doing the math.

Eric