Hello, I had posted some time ago with a high-speed vibration complaint with my 2000 Explorer Sport 2wd. I had BF Goodrich 30x9.50 tires on the vehicle at that time. Replaced the rear shocks and the vibration went away for a bit but then came back about a month later worse than ever. So I got the tires replaced though they looked new; should have listened to Jim Warman when he suggested that first but it was too tempting to spend $40 on rear shocks than a few hundred on tires. I got the tires replaced with Michelin LTX M/S 275/75R15 (stock size i.e.) and the truck is now back to being smoother than ever. It rides way better, is much quieter than before, and does not seem to have any noticeable vibration at any speed. As a bonus, the fuel mileage has improved a bit and it is no longer prone to violent bump steer as before. So thanks for the tire recommendation, Jim :).
I must also give kudos to Discount Tire. They had sold me the BFG tires originally and they took em in for trade cause they had barely worn out; with 40k miles on em, the tires looked as good as new. I got a pretty good deal on the Michelins and it all softened the financial impact a bit. I also learnt about "high flotation tires" though I am still vague on what that term means so any explanations appreciated :).
Once again, I am happy with my Explorer though I was seriously thinking of trading it in because of this issue. Sanity took over and I realized that the trade-in loss would be much worse than taking a final gamble on the tires. Changing the tires and the tranny fluid (manual tranny was getting hard to shift with 42k on the truck) has really helped the truck a lot; I went with Redline D4 ATF since it met the Dexron III requirement that Ford has for the manual tranny.
Hope this helps someone else out there dealing with a similar problem.
Regards, AB.