FINALLY! $800+ later my 1996 Exlplorer Sport (4L) is vibration-free!!! WHOOOP!

Symptom: Front end vibration starting at 45mph god awful at 75. Tires Balanced... twice no luck. Rotated and Balance.. nope. Bad lower ball joints... changed by some MF greaser at Brakes Plus (broke ABS sensor - replace both for free)... bill total $380 .. nope, still vibrating through dash. Both front bearings... did it myself (easier than you think - kick myself for not doing the ball joints)... $180 each... nope. CV's? Ack! Don't want to get back in there, again...more research... U-joints. Checked (on vehicle) seemed OK.

This vibration is driving me nutz. More research... U-joints... Cardan Joint? On front of rear driveshaft? What's that? It's a CV joint for the driveshaft. But all U-joints show no end play... Ok drop the rear driveshaft.

AAAAAAAAAAAHHHHHHHHHHHHAAAAAAAAAAA!

The CENTERING BALL FOR THE REAR CARDAN JOINT IS DRY A BONE!!! Bearings are dust!

Replaced with NAPA part #617 -- Ball Repair Kit - $34 (Front U-joints-- #5153X @$12). Also, replaced other rear u-joint with Autozone off the shelf (#2-4801 @$12) and greased splined slip joint. Replaced, and vibration is GONE!!!!!!!!!!!!!! Whoop!

THANKS TO: Keith at another ford forum: http://www.superford.org/registry/ve...id=139&s=13394 -------> see picture 3, showing exposed centering ball - *******o!

BTW: Ford Maintenance schedule for Cardan Ball Joint regreasing EVERY 10,000 MILES! There is a 1/32" diameter port on the front of the yoke to do this... no zerk. That would be too easy. Another Detroit brainchild at work here. The stupid Ford Parts Counterman didn't even know what it was... servicing HAH! Ford doesn't stock the parts!

PS: If you rebuild it yourself... DO NOT DESTROY the centering ball boot, I had to reuse mine -- couldn't find a replacement! Also use some threadlok on those Driveshaft bolts!

Moral to the story... you need to drop the Driveshaft to check it right!

Next... Explorer express drop kit and 4.0 Liter supercharger.

Hope this helps somebody! Most FORD LT's are equiped with the Cardan Joint on the rear driveshaft and from what I have read is probably causing ALOT of the vibration problems.