speedometer pinion

["Evangelos G. Makris" <emakris@hol.gr>]

Thanks to all the people who responded to my wipers question.

Now, is it possible to replace the speedometer pinion (and
its "housing assembly") with the engine/transmission in place?

Since these are made of plastic (?) I suspect them to be 
the reason why my speedometer shows what it fancies whenever
it does so..(it shows less or nothing when the car warms up).

Evangelos 
66 HAN8