I have an auto 2005 Mustang GT and when I go 90 or above mph the driver's seat and I believe the passanger's seat vibrates like crazy... is this normal??

 

Don't know about the driver, but maybe the passenger is nervous?

Seriously, I haven't noticed it, but I don't spend a lot of time at those speeds. At 80-85, I don't notice a problem.

 

Negative Ghost Rider. Inspect your wheels for debris on the inside of the wheels. I once had a dead mouse stuck to the inside of a wheel. SHook like crazy.

If nothing found, get all 4 balanced and rotated.

Good luck!

 

is it the seats... or can you feel it in the steering wheel? I'd agree it's most likely in need of a good tire balance.

 

nope the seats... u can feel it in your butt, vibration is more towards the middle of the car

 

Agree with above, if you can feel it in the seat, you have a tire balance problem, most likely a rear tire. (old rule of thumb, in the seats - rear tires, in the steering wheel-front tires)

 

If the passenger seat is empty, I can see it vibrating at 80+ mph--but I can't feel any vibration in the driver's seat so I don't care.

 

yeah you can definately FEEL it in the drivers seat. like your butt is getting a massage. Im thinking it's not normal then if everyone here hasnt experienced it...

 

then yeah get your tires balanced, even if they are still the factory wheels, i have heard people talk about loseing the little weights on the rims sometimes, when even one comes off the whole car goes crazy

 

True. But you don't need to throw a weight to be out-of-balance. Just a few thousand miles of tire wear can be enough to require wheel rebalance.

 

Would my tires cause me to have a vibration in my seats? The vibration in the seat is more towards the middle of the car.

 

It is the first thing to rule out before looking at other drive train problems. A vibration in the steering wheel is usually the front tires, where an out of balance rear tire would be more likely to show up in the seats or floor area. I'd take it to a good tire shop and have them balance and rotate the tires. They probably need it anyway if you have 5-7 thousand miles on the car.