I believe the best format for 3D Translation right now is STEP. The way that it was described to me is that IGES standards have a wide variety of potential variations (and config options)that are still considered to be standard in the IGES world. For example, the CAD system performing the export may have different IGES config settings than the importing CAD system. This is the reason why there may appear to be errors in an imported IGES file even though there is probably nothing actually wrong with the IGES file itself.
STEP standards tend to be a bit stricter than IGES standards and therefore, data translates much cleaner and you typically don't have to worry as much about the configuration options you set.
I tried the SAT (acis) format using pro/e 2001 that seemed to be a good solution (autocad support this format ). The only restriction is Pro/E sat format is lev 5.xx and acad st format is 3.xx. Is there a way too convert sat 5.xx to sat 3.xx.
You can get XchangeWorks at www.xchangeworks.com This is a free software for translating solids into AutoCad. It has several different types of translations. It has worked well for me in the past. The website has the details. Good luck.