Question
'Assalaamu 'alaikum wa rahmatullahi wa barakatuh,

How do the articulation points and/or characteristics of the raa’ and the laam change when they have tafkheem?

Jazakallahu khairan,
Was-salaamu 'alaikum wa rahmatullaahi wa barakaatuh.

Answer
Wa alaikum assalaam wa rahmatullahi wa barakatuh,
Neither the articulation points nor the characteristics change on the letters  and  when they have tafkheem.  Since the characteristics of the letters that outlined by the scholars in pairs of opposites and those without opposites are intrinsic characteristics in those letters,  the and and are considered to have and not .  Only the letters in the group have . 
The letters andhave tafkheem in some cases and other cases not, so what changes is the position of the posterior (deepest part) of the tongue and the focus of the sound in the mouth when they have tafkheem.  This is called the tafkheem mechanism, and more specifically it  is: elevating the posterior tongue to the roof of the mouth (soft palate), creating more space between the roof of the mouth and the bottom of the mouth, and focusing the pressure of the sound of the letter to the roof of the mouth (the hard palate area).  The articulation point of both letters stays the same whether they have tafkheem or tarqeeq, the only thing that changes is the position of the posterior part of the tongue and space in the mouth and the focus of the pressure of the sound. 

Please see:
http://www.abouttajweed.com/tafkheem-and-tarqeeq/tafkheem-and-tarqeeq-part-1.html
http://www.abouttajweed.com/tafkheem-and-tarqeeq/tafkheem-and-tarqeeq-part-2.html
http://www.abouttajweed.com/tafkheem-and-tarqeeq/tafkheem-and-tarqeeq-part-3.html
http://www.abouttajweed.com/tafkheem-and-tarqeeq/tafkheem-and-tarqeeq-part-4.html


Wa iyyaakum.  Wa assalaam alaikum wa rahmatullahi wa barakatuh