In the latter part of the phrase in question, three distinct wordings are possible: (1) "not all cars are made equal", (2) "all cars are not made equal", and (3) "all cars are made not equal". The respective meanings seem to be (1) "some cars are made differently", (2) unclear, and (3) "every car is made differently".
I regard (2) as unclear because we are told that cars are "not made equal", that is, we are told something they are not, but we are not told what they are. I find it difficult to determine the exact meaning of "all cars are not made equal" and regard it as ambiguous. For further discussion of the problem see wikipedia re excluded middle: "Many modern logic systems reject the law of excluded middle, replacing it with the concept of negation as failure. That is, there is a third possibility: the truth of a proposition is unknown."
However, one of the answers to the recent question GEdgar refers to may be relevant. In that questionthat question the process of "negative raising (shifted or transferred negation)"](http://www.englishcorner.vacau.com/grammar/rules/raising.html) is mentioned, in terms of English-speaking habits: "When we express negative ideas with verbs like think, believe, etc., we prefer to make the first verb negative instead of the second. We shift or transfer the negative from the second verb to the first." By a similar process, many English-speakers will fail to distinguish between (1) and (2), but certainly would distinguish between (2) and (3).