2008 Mustang GT Vibration in Entire Car

Hey guys , really looking to get to the bottom of this... I had taken my car to my local Gerald's who do good work. And they checked my entire front end. Called me and said that the passenger outer tie rod was shot, driver inner tie rod shot, bushings for my front suspension shot, front/rear sway bar bushings shot, and finally my lower control arm bushings were shot. SO after all that i figured my vibration problems would all go away!! A front end alignment and 1,000 dollars later I take it on the road around town and test it out.

The car now drives great around town like it did when it was brand new, all the way up until you reach about 45-50 when you feel a slight up and down motion in the entire car, nothing extreme. But then you hit 60-70 and I can see my passenger seat shaking sometimes, as well as my dash, and just about everything in the car. Now I know the vibration is NOT coming from the front end after having all that done. So it must be elsewhere.

A few years back my Dad and I did 3.73 gear install and had bad aligning paint for making sure the gear pattern was correct. So sadly i had a slight howl on deceleration. We ended up getting new paint and set it up properly; however it still had a howl on deceleration since we drove a bit on it.. Fast forward a few years in the future and the gear starts leaking some fluid slightly. Decided its time to install a new fresh one the right way from a reputable performance shop. I purchased ford performance 3.73 gears and a cobra fully assembled diff to all fit together. Now the rear end is perfectly setup with no leak, and no howl on deceleration or acceleration, just like it should be. So the noise should NOT be coming from the rear gear.

Only other thing I'm starting to rule out is my driveshaft. Would an aluminum driveshaft fix my issue? Has anyone else had this problem with their S197 after gear installs? I didn't have the 3.31 stock gears on long and don't really remember the ride quality at high speeds since it was so long ago...

ANY help would be greatly appreciated! I just want that quality ride back in my stang! I know it isn't a Rolls Royce but my passenger seat shouldn't be having these vibrations at highish speeds...

Bullitt95 said:

Higher ratio axle gears will make the driveshaft spin faster at any given road speed so they can exaggerate a pre-existing problem. The center bearing is usually the part that wears out first and causes some rumbling, so I suggest you have the car raised on a lift to check the center bearing and U-joints for excessive play.

Click to expand...

Do you know what they typically charge for the parts and labor on that? I saw other people recommending a Ford racing aluminum driveshaft. But if I could not drop $700+ on a new driveshaft, that would be great.