Driven5 wrote:
I think your original thoughts are on the right path, and would probably try not overthink it too much beyond that.
Plenty of 7's (including Caterham's) have oil pans hanging lower than the frame and run up to 6" or so for frame clearance because of it. Probably the most common tire sizes have around a 23" diameter. So if you don't let the oil pan hang below the bottom of the frame and trade up to common 215/75-15 or 235/75-15 all-terrain tires, then that should immediately put you in the 8-9 inch clearance range without even changing anything else in the suspension.
The roll centers moving up with the sprung mass should be fine, and will mostly just help keep body roll in check. The only real geometry concerns I'd see are scrub radius decreasing and trail increasing in the front. Running a lower offset wheels should correct the scrub radius, and the mechanical trail increase shouldn't cause any significant issues. Obviously there are a few other (potential) tire to body/frame considerations to watch out for, but that just means a bit of planning ahead.
Alternatively...Jeep Cherokee donor?
I haven't decided on uprights yet, although leaning towards front S-10 blazer all the way around or Solstice. I like that the Solstice are aluminum, but I also like that the the blazers come off a vehicle designed for 4wd. Blazers also came with 15" wheels IIRC. I think the stock Solstice brakes require a 16" wheel minimum (although there are obviously workarounds). Thinking I should maybe have longer control arms to preserve turning radius with larger diameter tires. I'll have to draw it out first.
I do plan on using the Cherokee xfer case. I have the NP242 in mine which has a differential to give what is essentially AWD and then has full time 4wd, full time 4wd lo and 2wd. I rarely, if ever, run mine on the differential, but it doesn't have enough power to spin the rear wheels unless I'm in a situation were 4wd makes sense. That could be different in a lighter vehicle with more power.
Still undecided on the drivetrain, but I'm leaning towards the Cadillac 4.9 because of the light weight and simple design, mated up to an AR5 out of a Colorado pickup.
But, at least in my mind, the drivetrain is the easy part. The rest of the package needs to be sorted in my head first.
Fun fact... the solstice front and rear spindles use the same hub assembly- both can be driven. I'm currently in the process of determining how to use cobalt hubs on the solstice spindles so that I can use 4x100 wheels and smaller caliper/rotors.