<snip>
The last year for the 091 tranny was 83. The 85 and 87 should both have
091/1 but with minor differences inside.  All US waterboxer 4 speeds are
interchangeable. Near one of the bottom corners of the tranny is the ID
# starting with 2 or 3 letters. Here is a partial list of 4 speeds.

DK, DM, DZ - 091 trannys 80-83 in US. (Air cooled and Diesel)

DU, ABD, ACW - 091/1 trannys 83.5-91 in US. (Waterboxers)

Mark
<snip>

In support of Mark's note that all US waterboxer 4 speeds are
interchangeable:

I have an 84 with a rebuilt trannie from the PO (I assume they just swapped
in the rebuild instead of rebuilding the original). It's trannie code is
ABD0602 5. Not finding ABD in Bentley, I wanted to figure out whether it was
a 091 or an 091/1. It matched the drawings of the 091/1 in the Bentley, but
those drawings said that trannie was only for an 85 MV or something oddly
specific.

I asked the dealer. He told me the ABD was manufactured from 8/84 to 7/85
and was technically an 85 trannie, obviously compatible with my 84. Its part
number is 091 300 044SX.

So if anyone has an ABD trannie and wondered what it is. . . now you know.
Also, for those who haven't read every word of the Bentley, the second part
of the code is the date of manufacture. So my code is ABD0602 5 means it was
made June 2nd of 1985 (or was what Feb 6th?, but who cares?).

Steve