Platform, what does it mean? (sorry, long)

[Peter & Rebecca Lines]

PerL's list of VW/Audi platforms was correct, and informative.  I'd like to 
expand the definition a bit...
The basic idea is that the automaker wants to build as many different cars 
as possible without creating a whole bunch of new parts and a special 
factory for each one.  In the case of a "platform" they are referring to 
the basic dimensions that make up the unibody or frame.  Auto manufacturing 
engineers would say the car has the same "hard points".  This means that 
during the manufacturing process, the different car's unibodies would be 
held in a common weld jig, and would travel down the same assembly line, 
using the same tooling.  With the A4 and Passat, the floorpan of the Passat 
is stretched by an inch or two, but they fit into the same assembly 
tooling.  As Per mentioned, they may add different engines of a common 
family, different suspension tuning setup, etc... to make the car feel and 
look unique.  In fact, the car may be totally indistiguishable from its 
platform mates.  For example, a Dodge Neon and a Chrysler PT cruiser are 
built on the same platform, but all exterior sheetmetal is totally 
different.  Another example is a Honda Odyssey minivan and the new Acura 
MDX SUV, same platform, no visible resemblence.  And of course there are 
the Caddila-PontiaChevrOldsomoBuick contraptions that GM sells.  I really 
can't figure this one out, but alot of people actually think there is a 
difference between GM "brands".  VW Group is pretty much the acknowledged 
king of platform sharing.  The thing that makes them so great is not that 
they get so many different cars out of a single platform, but all the cars 
have a unique character.  Can't say that for any GM cars...  And I 
certainly would never confuse the driving feel of my GTI with a new TT, 
either.

One more detail that is sometimes confusing.  VW gives the A,B,C,D 
platforms numbers in succesive generations when the platform has a major 
redesign.  I would refer to my '98 GTI as being built on the A3 platform. 
 The '99 and later ones are built on the A4 platform.  However this has 
nothing to do with the Audi A4 model, which is built on the B platform. 
 Confused yet?  Good :-)

-Peter Lines
'86 4kq
'98 GTI