We just bought a used Transit 350 and whenever I go over a bump (sometimes even just a rock) or if I turn the wheels while braking, and sometimes even when I simply brake, we hear a loud knocking noise that's so loud, we think we might have run over/into something. The first time we stopped the van and got out to see what it was that we hit. Nothing there.
I've only had the transit for a week, and I plan to take it in to the dealer tomorrow and would like some info on how to address this quickly.
BTW, I rented a Transit for a few days before we bought one, and it had no knocking sound--it drove beautifully.