differential

Mouse here's a book on repair, modifying, and setting up differentials. Haven't seen it but the description sounds like it might be pretty good

http://www.ringpinion.com/b2c/ProductDetails.aspx?ProdID=6660&Product=RPSBOOK-01&Brand=RANDYS_Worldwide_Automotive&ShowAA=True&Year=1970&Model=Charger&DriveType=Rear%20Diff%20-%20RWD&DiffId=108&Source=DiffWizard