I found a pretty good way now how to translate an AutoCAD drawing using Trados. Just follow the instructions below and feel free to improve my proceeding.

Download the free Trans tool from xanadu.cz under http://www.xanadu.cz/dl_file.asp?ID=247 and unzip it.
Open the drawing you want to translate in AutoCAD
Load TRANS.VLX using the command line command Appload
Enter the command TR_WRITE in the command line and press Enter
Select the txt file for output
Select the complete drawing or the parts of the drawing you want to translate and press Enter
Open the exported txt file in Word and save it as rtf
Translate the rtf file with Trados
Do not change the text in parenthesis {}
Clean the translated rtf file
Open the cleaned rtf file and save it as txt (only text)
Change back to AutoCAD and enter the command TR_READ in the command line and press Enter
Locate the translated txt file
The text in your drawing will be replaced with the translated text
Additional hints: Be sure that no text layers are locked and try to keep the translated text as long as the original text for space critical situations

Thanks to the XANADU team for this great free tool. It is absolutely helpful.