Had a strange thing happen to our '97 GT 5spd wagon last night. Coming home from a weekend road trip, we're cruising through a canyon, my wife driving. Her canyon cruising is pretty conservative, but from the shotgun seat I can feel a thump-thump type of vibration on left-hand turns. I'm thinking a tire's going soft, but it's getting more obvious and doesn't seem to be effecting steering effort. She's getting concerned (me too), so we pull over and it happens when she applies the brakes, too. I pull the LF tire -- the tire's not soft, the wheel's solid, the lugnuts tight. I inspect the rotor and caliper, check the hub for any play or odd motion, rock and rotate the axle to see if anything clunks or looks out of whack. I'm finding zero, so I put the tire back on and run it up and down the highway to see if I can recreate it -- but nothing's happening. So I scratch my head for awhile, then cinch up my boxers and decide to limp it homeward. The longer I drive, the weirder it gets that nothing odd is going on! I'm back to cruising at 70 and there's no vibration -- nothing -- for the remaining 1 1/2 hours of the trip. Drive the car today -- nothing.

Could it somehow be a CV joint or differential issue? I'm really hoping for an explanation on this one -- it's pretty spooky

 

It's hard to say. Wheel-hop over undulations in the road?