[99monster stang]

So I purchased my 99 cobra a few weeks ago, and im noticing a loud and pretty strong vibration when im ONLY at speeds of 80 or higher on the highway. I never feel it when im in the city doing 60ish. If i had to describe how it feels, its like when your on the highway and drift to the side and you hit those ridges that let you know your going too far off the road. It makes a noise and strong vibration, if i had to guess its coming from the rear. Right before i bought it the guy swapped in a 02 gt 8.8 rear end with 3.73 gears. Im not sure if theres something loose or something, but any help would be appreciated! :bigthumbsup

 

[2Manystangs]

probably didn't set the lash correctly on the gears...stop driving it until someone who knows what is what checks it out

 

[99monster stang]

Gears came into mind, but why only in excess of 80mph?

 

[2Manystangs]

I'm not an engineer but it may be the point where the lack of the correct lash setting becomes an issue...if it's set incorrectly the gears are not meshing correctly...
Once again, I'd let a rear end mechanic check it out...it can fail is not set properly

 

[99monster stang]

Ok ill have to get it checked, but before i go this weekend, any other crazy possibilities it may be that i can check?

 

[2Manystangs]

the only other thing I can think of is to see if the car has a broken rear sway bar, it makes that sound you describe when it breaks, it may appear solid, pull on both ends and make sure it's solid

 

[hotcobra03]

tires are big on noises also...even if they are balanced..

my first thought would be try different wheels on car..got any friends with a mustang?

you can try rotating if wheels are same size..noise might move to front if in rubber

i have had this happen to me just not on my mustang...anything over 80 it would make strange noises..kinda like rumble strip

 

[gdp2001]

+1 on checking the wheels/tires. Had a tire on the minivan that did that but it started at 35-40mph. It could not be balanced out either. Bad tire.