The concept of this yoga has been bothering me.  Yes I have it in my chart, so I may be somewhat biased, but to be honest even if it wasn't in my chart it still wouldn't make sense to me.  

Rahu has always been described as an indicator for obsession.  Whatever Rahu touches, the native is usually vaulted into that direction.  Though I may get some disagreements with this statement, Rahu is actually quite similar to Guru. Guru and Rahu both signify areas of focused thought(though they work in very different ways).  Guru usually signifies the area of wisdom and philosophy for the person.   Rahu always amplifies its area of effect through focus and desire (Rahu always gets what it wants).  People commonly state that Rahu is about "material" obsession, and this is true in a sense.  Obsessions are always material in a certain extent because they are of the mind.  By material, it doesn't mean material property(making money and accumulating power).  Earthly existence itself is material.  Guru itself is a materially focused planet.  

If Rahu is with Guru, it amplify and makes the native obsess about Guru and Guru controlled regions.  Wouldn't that make the native obsess over their philosophy and finding truth?  Whether or not this is a good thing should depend on the location of Guru.

Rahu and ketu considered shadow planets. their attributes/ character is difficult to describe as they tend to get attributes of the house lord where they are hosted in.

Also if there any planets along with them then those planets will be eclipsed. Rahu and ketu love Sun and Moon. when sun and moon are associated then they create max impact.

In case of jupiter being with rahu makes Jupiter eclipsed by rahu. Jupiter represents wisdom/dharma. being eclipsed implies main functions are troubled. Its like cancer affecting the body part. Jupiter being deva guru/ represents wisdom/education/dharma etc etc. Rahu and ketu ( once monster) eclipsing Jupiter implies Jupiter not allowed to perform his functions. This brings period where wisdom/dharma looses focus and materialistic elements replace it.

Rahu and Ketu not only "eclipse" planets, but they "eclipse" the space that they involve as well.  To say that rahu effects planets differently than it effects the space that it occupies doesn't make too much sense to me.  Jupiter does represent wisdom, I'm just not sure why rahu is looked at as a "cancer" or the materialistic node. From the ways I've heard many astrologers talk of Rahu, it is a node of obsession or focus.  Rahu is basically never satisfied.  Where ever the node lies is a place where the native's focus is aimed towards.   Thinking about the two combining together, it would seem that they would combine to create an obsession with wisdom and truth-seeking(the house  and rasi depicts the type of truth).  Sort of an entitlement to wisdom.  To say that it is like a "cancer" or it is evil or demon-like doesn't really make much sense.  

Rahu does hate boundaries, but boundaries don't lead to truth.  Truth is boundless.

Know what.....Guru chandala was interpreted in spirirual terms by sages.
In todays' world Guru chandala yoga is good cuz it actually wud make u more practical in money or material matters .  .It is chandala in sense of keeping ur belief shaky in spiritualism, good ness and satvikta...also depending upon horoscope some corporal non-corporal matter may change as well with conjunction ...Guru being disturbed by Rahu.

namaskaar Sg ji,
Guru Chandala good?
Do you know that in certain combinations it represents Jeeva Hatya?
vivek.