Florid to Northern Michigan

75-475-23-75

By far the best and fastest route. Avoid Detroit with every option!!!!

Personally I always try to avoid I-75, especially through Ohio. Lots of truck traffic, but then again, there's always truck traffic on all Interstates. Cincinnati can get pretty crowded from northern KY to north of Dayton.

Option 1: I-75 north through Kentucky, but catch I-275 just south of Cincinnati over to I-74 to Indianapolis and then catch I-69 north of Indy.

Option 2: I-75 to Atlanta and then northwest to Nashville via I-24. Then north on I-65 to Indy and I-69 north to Michigan.

Option 3: This is the route many Michiganders take to & from Florida when snowbirding. I-10 over to US231, then north to Montgomery and then I-65 up through Indianapolis and I-69 north to Lansing. You can catch US127 north of Lansing, MI and eventually catch I-75 near Grayling, MI. This route will have significantly less elevation changes as you miss the Smokies in TN and KY.

I would second 475 to 23. Any route that by-passes Detroit is a good one as far as I'm concerned.
Regarding Atlanta, we time our trip to go through on a Sunday morning when the only folks on the road are truckers and church-goers.

I would go I-75 to just south of Toledo, OH and take I-475 around to 23. 23 meets up with I-75 again south of Flint and you avoid Detroit. Nice stop is Cabala's in Dundee, MI has a dump station and allows dry over night camping in the north west parking lot.

I prefer to avoid Louisville if at all possible. Having had several bad experiences there. Never had an accident but it seems as though the area around the I 65 Bridge over the Ohio has it in for me. Cincinnati always seems to me to be a more affable drive. I 75 last time I drove through the route in '09 was in better shape . I 65 needs major improvement through Indiana (which is where I travel).