Is it ever explained how Chewbacca...
 

goes from being like the #2 Wookie leader to co-pilot on a dingy, second rate freightor?

Maybe Owen molested him.

Outside the movies, it's always been said Chewbacca's planet was enslaved. Chewbacca escaped it, or whatever.

Sound fairly reasonable.

Han broke Chewie outta slavery.

and ended his (han's) imperial career

This isn't in responce to your question - but it's Wookie related and i didn't think it was worth it's own thread -

In Star Wars creatures on A&E, Peter Mathew said that he was told the Wookies live in trees. They don't speak but they do understand. I always though that they did speak and that only a few understood them.

Second rate freighter? Dude! It made the Kessel run in less then 12 parsecs! ;)

Given what we see in Ep III, why doesn't Chewbacca give any indication that he is intimately aware of the Jedi and their fight? Seems as if the whole Wookie thing was put in just to be put in.

yup.

Chewbacca undertook a Wookiee "life debt" to Han Solo due to Solo saving his life at some point before A New Hope, probably when Han broke him out of slavery

at the very least putting chewie in was just to make the fanboys cream

Not really, fanboys cream at a young Boba Fett and other random obscure characters...Chewbacca gives the masses something to relate back to the original trilogy.

after the war, chewie learned to "punch it"

but there was no use for a "punch it" guy on kashyyk

Don't forget Chewie brings Obi Wan to Han. Don't forget he is the one who wants Han to stay and help. He appears to understand what is going on, we just don't know what he is saying.

YOUNG GWEEDO RULEZ!!! (ep 1)

Did Chewie and obi ever meet in ep.3? Not that i remember. So there is no connection to him in episode 4. So chewie only met Yoda. Did Chewie ever see yoda in ep.4-6? No. So there is no connection HE would be aware of. WE are aware of everything, but he was on his home planet and only dealt with Yoda, unless I am missing something.

Well Chewbacca most certainly saw OBi-Wan teaching Luke with a lightsaber, and talking about the Force. You think he would most certainly correct Han about his misbelief in the Force.

And you think Han would believe him?

"Get in there, you big furry oaf!"

Chewie only saw Yoda flip around and kill two Clone Troopers with his light saber, not much of a force move. He may have only seen Yoda as a great leader, not as a great Jedi Master. Then it is about 20 years before he sees a Jedi again.

Yoda said he a good relationship with the Wookies, not Chebacca.

He obviously had a relationship with Chewbacca. He called him by name. And jumped on his back in retreat.

lol, for some reason this reminds me of something Mitch Hedberg would say.

Well put. Also, Chewie doesn't strike me as a character who was exactly verbose with his feelings. What was he going to say "Wow! I haven't seen a Jedi since Master Yoda fled my planet immediately before the rise of the Empire!"

wrap your brain around this one... If Chewie owes han a life debt for saving him... does Yoda currently owe chewie a life debt for getting him out of harms way?

THINK ABOUT THAT SUCKER!

anyhow. it's clear that Chewie's moans are like folks talking to their pet dogs when they bark. They put in words for them in a sense. So it's all other means of communication.

That doesn't mesh with the following dialogue from episode IV...

Chewbacca: Rarrgh rerrrr rarrgh ra.

Han Solo: Boy you said it Chewie. (To Luke) Where did you dig up that old fossil?

Right, but up until the Mos Eisley he had never met Obi-Wan. I got the feeling it was being inferred sine Ben talks to Chewie first about getting a ride on the Falcon.

Obi Wan could have easily messed with Chewies mind to get him to take them to Han about hopping a ride out of dodge.

And what exactly would Chewies stance be anyway? So, Han doesn't believe in the force. Chewie has to believe the same thing because he is his co-pilot? He is a different race from a different planet who probably has his own beliefs. Why would he have to correct Han about the force exactly?