Since we're speaking in general here, id like to say that in MY experience with import 4x4's THEY are the ones making garbage.
My last Toyota 4x4 was always breaking something, i hated it!
Not to mention that most all my buddies with Toyotas that 4 wheel for recreation all have aftermarket parts in their trucks due to easy breakage.
Not bad 4x4's when upgraded though.
My last Chevy Z-71 was a dream! Always got me to my hunting lease and through some crazy stuff. NEVER had a problem with it. I sure hated selling her last month

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I guess if you just want something to get you to work you could go import. Great realiablity on the street and good gas mileage
Anyway, i dont think you should worry about the 4x4 engaging in low on the highway. Im not certain about Ford, but i dont think theres a problem driving in 4x4H on the highway.
Of course, its not ok for it to happen all on its own. I hope you can get it fixed.