Robert -
Here's what I can tell you about the Whirlpool line during and after the 1982 machines were offered:
First, the 82's were the first machines designed for the revised baseplate and new basket/tub sizes. The previous 1980/81 models were easily revised to have the new baseplate and other parts, and consumers probably only rarely even noticed. BUT, the '82s had new console graphics, which were used on most all machines, TOL to barely MOL. The 1982 machines were LA....XK models.
Oddly, models were developed for 1984 which look absolutely identical to most or their counterpart 1982 machines. I have a WP LA7680XK right next to an LA7680XM (XM is the '84) and it beats me if there is any difference. I've stood there looking for something as minor as a print font or wording change...nothing. The '84s looked just like the '82s.
The 1985 models, addressing a point you made above, were a little bit different, most of them anyway. These were LA....XP models, and many of the XPs have single sloped consoles, new knobs, a woodgrain stripe toward the top of the console, and no secondary little "lip" on the top of the panel. Oddly, before I bought my '86 Kenmores I had ordered in late June 1986 a Whirlpool LA5580XP - but it retained the older console of the 82 and 84 models. It was a Circuit City model, and often they had models custom made for them so their absolute price guarantee could never actually be used since nobody else had the exact model. I believe that most full-line WP machines for places other than Circuit City had the new console.
This didn't change the machines much though other than the minor appearance change. Some of the older models seem to have remainined in production for a while, and the XPs were basically the same feature-wise as the XMs. The last major change Whirlpool made to the belt-drives was in moving to the basket mounted lint filters (and thus removing a lot of hoses and parts) which was done in summer 1982. After that, the machines coasted until the DDs came in.
The BDs went out with a bang so to speak though, as 1984-1986 was a HUGE production period for them, and for appliances in general as the US economy recovered from the late 1980-1983 recession, and the assembly plants in Clyde and St. Joe were on overtime many days to keep up with backlogs. Today, it is very common, and much more likely, to find a LA....XM or XP machine vs. an XK, not because they are a tad newer, but because the XMs and XPs sold in so drastically higher numbers.
Cool stuff Robert, thanks!
Gordon