Assuming that the wallet.dat file is really yours and that you didn't bought it in the hopes of finding the password (who locks almost 3 bitcoin without noting down the password ?), I really don't see how you can achieve this. My first suggestion would be using John the ripper[1] and hascat[2] but TrueCrypt has near perfect cryptography and these tools would probably only help you in finding one or two characters at most. If the password was complex and had a mix of numbers and special characters I would say forget it but perhaps someone who is more knowledgeable in this matter will show up with a better solution than mine.

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[1]https://www.openwall.com/john/
[2]https://hashcat.net/hashcat/