Hi goat4444,
You can use any 3D modeler like 3DS Max to make a car model with poseable parts.
If I understand your question correctly, you'd like to use the car model in Poser. Here is a brief overview of the major steps:
1. Prepare the geometry for your Poser model.
The car model in Poser is a figure with several body parts. Poser will load the model from (usually) a single Wavefront .obj geometry file.
The .obj file must have group definitions, that is, each part of the geometry is a group with a group name. You can define and export .obj groups in 3DS Max and most other 3D modelers.
The groups in the .obj file are used to identify the parts in Poser. Usually, each group in the .obj file is an actor (body part) of the Poser figure. The .obj file of the car model has for example groups "car", "steering", "pedal", etc. The Poser figure library has actors "car", "steering", "pedal", etc. Poser treats the corresponding geometry group as a separate object.
There are other ways to achieve the same result: You can create the parts separately and load each part into Poser. Then you assemble the parts (car, steering, pedals, etc.) in Poser and export all parts from Poser to a single .obj file. When you use the proper export options, each part will be a group in the .obj file.
Or, you define a Poser figure library which uses many different .obj files, one for each actor. In this case, you simply create an .obj file for the car, one for the steering, another one for the pedal, etc. In the Poser figure library, actor "car" will load the "car.obj", actor "steering" will load the "steering.obj", etc.
2. Prepare the Poser figure library (.cr2).
When your figure .obj is ready, you define a .cr2 figure library to use the model in Poser. To create the .cr2 in Poser 5 or later, you can use one of the "rooms". There are several utility programs (I guess) which can create .cr2 libraries.
Alternatively, you can write a ".phi" text file ("Poser Hierarchy File") and use the "Convert Hierarchy File..." command to convert the .phi to a .cr2 library.
Your .cr2 file defines a hierarchy among the actors. For example, actor "steering" and "pedal" are children of actor "car". Furthermore, the .cr2 defines whether the seams of two actors are glued together or not. The parts of a car are typically not glued. The .cr2 can include additional actors which have no corresponding geometry.
The .cr2 defines a pivot ("origin") for each part, and "channels" to perform standard transformations (rotate, translate, scale, etc.). These standard channels are automatically included when Poser creates your .cr2.
3. Tune your .cr2.
Once your .cr2 exists, you can adjust the actors properties in Poser or edit the .cr2 in a text editor.
When you want a poseable steering wheel, for example, you center the pivot of actor "steering" and adjust the "orientation" angles if necessary. Poser displays dials for the "rotate" channels in the dials palette. To turn the steering wheel, you just set the proper "rotate" dial. You can rename dials, hide not used dials, and set channel limits, to make a user-friendly interface.
That's it. Since most of the parts of a car perform very simple motions, you don't need additional channel code. The opening doors, hood, trunk lid, wheels, and gauge needles are all simple rotations.
4. Customize your .cr2.
You can add non-standard code to your .cr2 if you want special behavior of your moving parts. You can for example use the "PointAt" constraint to implement automatic orientation of your moving parts, use "alternate geometry" to load or modify parts of the car model, or use Morph Targets to deform the geometry.
You can use "ERC" code to synchronize several moving parts. For example, you include code to turn the steering wheel and the front wheels accordingly when a single "Steer" dial is set.
To learn more about ERC code, you can download my ERC tutorial here:
http://www.atlantis23.com/erc_download.html
There is a code example for the steering mechanism in Chapter 3 of the tutorial.
Hope this is the information you're looking for.
VK