I think I posted this position earlier in the thread, but I'm gonna post it again since the IRS discussion is renewed.
There are a few things that bother me about the upcoming Tahoe's IRS.
1. GM has been dominating the segment for decades with a solid rear. I don't know if they're worried about a slight bump in Expedition sales, but I don't see the Expedition threatening the GM SUVs in any meaningful way in the future. It's had IRS since 2003 and has not eaten into the Tahoe's sales much if at all since then.
2. IRS is more expensive. GM is all about cost cutting, so why add cost here, and more to the point, why mess with a simple formula that has worked so well for so long?
3. People that are concerned with 3rd row space and ride already have an option - the Traverse. It's nearly as large as a Tahoe.
4. I am assuming the Silverado/Sierra half tons will have solid rears at least for the duration of the 2019-? generation. By putting two different axles on two different vehicles on the same platform, GM is implicitly admitting that one of the axles is a concession. I mean, if the IRS is so great, and if it can be implemented without affecting towing or payload, then why isn't it already on the Silverado/Sierra, which receive much more R&D dollars than the SUVs? The pickups and SUVs should be identical in all aspects besides sheet metal.