If you're getting 10 volts between the frame and the negative battery post you've got a very bad ground somewhere. It should be zero. Be sure there's a good ground strap from the engine block or the alternator housing to the frame, and attach the negative battery cable to the engine block somewhere, NOT the frame or body. It sounds like there's an insufficient, or maybe nonexistent ground from the engine to the body/frame assembly. Never, ever disconnect a ground or a hot cable with the engine running- - - -I've seen voltage spikes of over 100V on an oscilloscope just as the connection is broken.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!