My guess is that the clutch was adjusted with the cable too tight (barely engaging)
and that your 20 minutes in traffic, slipping the clutch, wiped it out.
A new clutch plate MIGHT fix it but you may also need a new pressure plate
and a little surfacing on the flywheel.
It DEFINITELY sounds like a clutch problem (with the smell) and not a tranny problem.
You need to have at least 3/4" of free travel in the clutch pedal before it hits
anything to make sure you get full pressure from the pressure plate on clutch engagement.
If you have no play, your clutch is not engaging fully and it WILL slip.
It doesn't have to slip very long before it burns and then it wears MUCH faster.
BTW US (left-hand drive) 164s come with a cable clutch, not hydraulic.
If the clutch throwout fork is properly installed it is nearly indestructible
but the arm that the cable hooks to, that turns the throwout shaft, is welded to
the shaft and I have seen that weld fail after several years with an extra-heavy-duty
Chevrolet clutch (which did NOT slip!). After that I went back to the standard OEM clutch.
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George Downs, Bartlesville, Heart of the USA!