I have a 92 Aerostar XLT Electronic 4wd. When driving down the road I feel a grinding underneath and it tries to pull me off the road. Plus I've had 2 flats in the last couple weeks.

Some Taurus models are known to have springs that break, causing flats. Never heard of it on an Aerostar, but there arent that many on the road. Check the wheel bearings, suspension and steering components.

Ok will do. The suspension seems fine, and this grinding isn't all the time, and feels like it's under the front seats.

Could also be an issue in the transmission or transfer case, but that certainly wouldnt cause a flat. Is it only when in four wheel drive, or does it occur in 2wd as well?

The 4wd is electronic so you can't tell when the 4wd kicks in.

Are the tires all stock and all the same size? I noticed that with the electronic AWD system, when i had to use the spare it acted really strange, especially around turns, probably thought it was slipping so it was always engaged/disengaging the 4wd system at higher speeds, maybe causing the grinding sound? Oversized tires might be an issue too, idk

All tires are same size with the exception of the spare which is just a little larger. Will replace the spare tonight and check it tomorrow.

I'm having this exact same problem, minus the flats. Did you ever resolve the issue? I know this is 5 years old...