Michigan and Indiana wanted to decommission US 27 way back in 1974

[Max Rockatansky]

If I recall correctly didn't MDOT relinquish much of Old US 27 once it was truncated?  I want to say some of it was retained by MDOT as US 127 Business near St Johns?  Either way Old US 27 north of Lansing was a pretty quality surface expressway for what it is.

A little bit of it. Business 127 turns east to go back to the freeway at Price Road. South of there I'm thinking it's now local control (Clinton County).

Actually, the old US-27 south of St. Johns to Grand River Ave. in Lansing is still under MDOT maintenance, as is old US-27 (Lansing Rd) SW of I-496 through Potterville and Charlotte to exit 57 of I-69 south of Charlotte.

Makes sense, that's a really high capacity road for those counties to assume maintenance of.   I'm kind of surprised it was never assigned a Trunkline Number that being the case. 

MDOT once considered renumbering Old US 27 along Lansing Road as a new M-442. That was around the same time they renumbered Old M-21 as M-121 in a bid to return unsigned highways to signed status.

Was the 442 a reference to Oldsmobile and it's presence in Lansing?

Ding ding ding!

Too bad that didn't happen, we could some muscle car themed highways. 

Yes, I was thinking the exact same thing, and perhaps throw in an M-500 for Cadillac and their behemoth V8 engine that existed way back when. (Of course, that's not a muscle car company, but still...)

With Lansing though I've always associated far more with Oldsmobile than Cadillac.  442 is about the only appropriate highway number unless you wanted wanted to sign the route as "Cutlass Supreme Memorial Highway"  or something like that.  Too bad M-88 is in use, that would be kind of funny given how much Delta 88s used to get ragged on. 

[rawmustard]

Actually, the old US-27 south of St. Johns to Grand River Ave. in Lansing is still under MDOT maintenance, as is old US-27 (Lansing Rd) SW of I-496 through Potterville and Charlotte to exit 57 of I-69 south of Charlotte.

The portion from I-69 Exits 61 to 70 was turned back to Eaton County back in 2008. (Chris Bessert for some reason erroneously lists the latter exit near the State Secondary Complex as 92.)

[GaryV]

how many unsigned state highways does michigan have?

40-ish.  See Chris Bessert's list:  http://michiganhighways.org/other/unsigned.html

[Flint1979]

The answer is 44.

13 mainline highways, 30 special routes and 1 business route.