Hello! My buddy just bought a 2016 L405 RR Si6 and I've been helping him with some maintenance items. I noticed it has aluminum front and rear subframes vs. stamped and welded steel on my L462 TD6. Most every other aspect of the suspension and underbody are identical. I can speculate why their different, but does anyone have any factual information why they deviate?

 

Strength - that's what JLR said when the L663 came out. The steel subframes can tackle more abuse that an L663 (and presumably L462) is more likely to go through compared to an L405.

IIRC, the new MLA-Flex platform that underpins the L460 & L461 uses steel subframes now. It is a mixed-metal architecture, and not as aluminum-based as the previous D7 platform.