Dodge Repair: Tranny prob, dodge grand caravan, 2005 dodge grand caravan

Question
2005 dodge grand caravan, 3.3L, 90k miles:
has been working fine until yesterday.  started it up to pull out of parking spot and put it in R and hit the throttle and it was like it was in N.  Put back in P and back to R and same thing.  Third time, as i was hitting the gas it made a loud clunk and finally went backwards. jerking a little. backed out of spot, put it in D and nothing, back to P and back to D and again a CLUNK and went fwd.    Towed it home on a rollback type trailer (winched it on) and when I got home, I got inside as my friend tilted the trailer.  My foot was on the brake, Shifted to N and it started to drift backwards but I stoped it as I figured I better start it so I would have brakes when rolling off the back of the trailer so I started it up.  I left off the brake and it was like it was in P.  I shifted back to P and then N and it drifted back just  mere inches like it was put back in park or something.  Back to P then N same thing just drifted about an inch (and remember the trailer is tilted UPWARDS so I should have been rolling freely backwards.)  I put it back to P then N and hit the gas...same thing (like it was in Park).  I put it back in Park then to Reverse and same thing when I took my foot off the brake it only moved about an inch or so (again like it was back in p).  My friend was in a big hurry with his trailer and so I put it in P and hit the gas and back to R and it  clunked and started backwards so I was able to get it off the trailer and park it.   I got the following codes from turning the key on-off-on-off-on:   -P0456, and -P0406 which I don't think have anyhyting to do with my problem although I do think I have a bad egr valve but have been meaning to try to clean it and see if i can get it working again. (I Lost my job a few months ago and have to watch what I spend right now).   ANY HELP or directions you could give me would be GREATLY APPRECIATED!!!!

Answer
Hi Jim,
The key dance doesn't usually readout the transmission controller codes; that requires a plug-in code reader. So about all I can suggest is that you check the level of transfluid by means of its separate dipstick and only use ATF+4 to fill it via the dipstick to the max. level cold.
Then have a helper move the gear shift lever to be sure that the shift rod on the transmission is rotating through the full range of positions at the ends of its travel.
Other than that see if you can borrow a plug-in reader and seek transmission fault codes. If you can get it to move reliably and a nationwide autoparts store, such as Autozone, is nearby see if you can get a free fault-code readout. Otherwise an independent shop will do it for around $40. Let me know fault codes which are mainly in the 700's and 1700's.
The codes you did get are about:
the egr valve positioning (which may just be a sticky movement of the valve stem so spray that with WD-40 on the stem where it enters the body of the valve and then move the stem back and forth with the tip of a screwdriver inserted in the slot on the stem),
the evap recovery system which has a leak (which may be a loose hose fitting anywhere in that system).
Let me know any trans codes that you find.
Please 'rate' my answer (see below).
Thanks,
Roland