Markschum has it.  For steering plain old ERC will do the job, as in his example.

You might want to look at Dependent Parameters for other controls if you're
going to make a completely posable car.   For example, a 5-speed stick shift
or accurate suspension motions.  ERC won't do those.

In P7 here's a script that makes it easier to set up DP, though not as
easy as the built-in system in P8.

http://ockhamsbungalow.com/Python/KeyframeERC.zip

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