The phonology of Modern Standard Albanian (MSA) discerns two laterals: a clear lateral and a dark lateral, e.g. “hallë” (aunt, dark lateral), “halë” (splinter, clear lateral). The articulatory difference between the two types of laterals is described for MSA as follows (see Ladefoged & Maddison 1996):

Clear Lateral Dark Lateral
Tongue tip (or blade) against the alveolar ridge Tongue tip behind the front incisors
Tongue body higher Tongue body lower
Nor retraction Back of the tongue retracted, narrowing of the pharynx

In the Viennese dialect, the clear lateral is velarised/pharyngealised in certain context, as e.g. word-initially, e.g., “Leiter” (ladder, dark lateral). The clear lateral is never velarised/pharyn¬gealised after bilabials or velars, e.g., “Blumen” (flowers, clear lateral) or “Glas” (glass, clear lateral). After bilabials, the clear lateral occasionally surfaces as a retroflex, after velars, it tends to be strongly palatalised (Moosmüller 2012).
As opposed to Modern Standard Albanian, the clear lateral of the Viennese dialect (and of German in general) is formed with the blade of the tongue against the alveolar ridge. Whether or not the blade or the tip of the tongue is involved in the production of the dark lateral is still a question of research.

From an acoustic point of view, the main difference between the two types of laterals lies in a high F2 for the clear lateral (~ 1300 – 1500 Hz) and a comparatively lower F2 for the dark lateral (~ 1000 – 1200 Hz). In addition, prominent zeros are introduced as a consequence of the side channel(s) and a supralingual cavity (Fant 1970, Stevens 1999, Zhang & Espy-Wilson 2004), especially in the region of F3. It has been observed that the zero for the dark lateral is slightly above F3, whereas it is slightly below F3 for the clear lateral (Müller 2011).

The main difference between MSA and the Viennese dialect lies in the fact that in MSA, two laterals are discerned phonologically, whereas in the Viennese dialect, the dark lateral is an allophone of the clear lateral. The question arises whether in the Viennese dialect, different degrees of darkness can be observed, whereas in MSA, dark and clear laterals have to be distinguished categorically, in order to avoid homophony.
It is a main research question, whether, in addition to F2, the position of zeros might shed light on the question of gradual versus categorical implementation of the dark lateral.

References:

Fant, Gunnar. 19702. Acoustic Theory of Speech Production. The Hague: Mouton.
Ladefoged, Peter & Ian Maddieson. 1996. The Sounds of the World’s Languages. Oxford, Cambridge: Blackwell Publishers.
Moosmüller, S. 2012. The roles of stereotypes, phonetic knowledge, and phonological knowledge in the evaluation of dialect authenticity. In: S. Calamai, C. Celata and L. Ciucci (eds.), Proceedings of 'Sociophonetics, at the crossroads of speech variation, processing and communication', Pisa, December 14th-15th, 2010. Pisa: Edizioni della Normale. ISBN (online version) 978-88-7642-434-2, 49-52. http://www.sns.it/scuola/edizioni/testionline/
Müller, Daniela. 2011. Developments of the Lateral in Occitan Dialects and their Romance and cross-linguistic context. PhD Thesis, Université de Toulouse and Universität Heidel¬berg.
Stevens, Kenneth N. 1999. Acoustic Phonetics. Cambridge Mass.: The MIT Press.
Wagner, Daniela. 2011.
Zhang, Zhaoyan & Carol Y. Espy-Wilson. 2004. A vocal-tract model of American English /l/. Journal of the Acoustical Society of America 115 (3), 1274-1280.