Transmission
Overdrive was optional from launch. The Borg-Warner DG250 three-speed automatic arrived during 1956, making the XK140 the first Jaguar sports car offered with one — though torque converter changes appear in the service bulletins from December 1955, so the development ran ahead of the announcement.
Doors — a correction worth making
A widely used buying guide states that the XK140's doors, bonnet and boot lid are aluminium, and advises checking the ash door frames.
For the XK140 this is wrong, and it matters because it sends buyers to make a check that tells them nothing.
Roadster doors were aluminium throughout. Early coupe and drophead doors had steel outer skins and steel shut-face panels over a timber frame, with aluminium only on the hinge face and bottom panels. From October 1956 they became steel entirely. We found no support at all for aluminium bonnets or boot lids on any XK140 — that is XK120 lore, and only early-XK120 lore at that.
The practical consequence: a magnet on a coupe door skin proves nothing, because the skin was steel to begin with.