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ST5 and 6 Subframe Modifications

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I'm looking for some guidance regarding intent, interpretation and enforcement vs the literal wording on subframes.


I see the intent is to prevent suspension geometry changes, but other stuff in the spirit of NASA ST, safety and reliability is allowed. 


What about welding brackets to a subframe for an engine swap? Engine mounts are not mentioned.

Modifying differential mounting points on a subframe that also mounts suspension?

The E46 M3 subframe is identical to E46 330, but has different differential mounting. To run a E46 dif to get access to an affordable limited slip, could someone run the E46 M3 subframe? Or would have to cut and paste the dif mounting points to follow the letter of the law?

Thank you!


"6.1.3 Chassis and Body Modification Limitations
Other than the listed exceptions, every vehicle must retain its unmodified:
1) OEM frame rails/rear frame cross beam, and/or Unibody, and Sub-frames/suspension
cross-members (in their OEM locations)."


"The following are the permitted exceptions to #1 above:
1a) Frame rails, sub-frames/suspension cross-members, and unibodies may have maximum
diameter 0.75” (3/4 inch) holes drilled into them for purposes other than lightening, such as for
the attachment of ancillary parts. Cutting and channeling is not permitted.
1d) Modifications of non-subframe/non-suspension cross-members (other than the rear frame
cross beam), transmission mounts, differential mounts, and radiator core supports are permitted.
1g) Reinforcement of suspension mounting locations on OEM frame rails,
Sub-frames/suspension cross-members, and unibody is permitted provided there is no
performance benefit or relocation of the mounting points. Seam welding of the body is permitted."

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