2005 auto mustang vibration noise/ rumbling noise

hi ppl
i was on the way back home in a rush so i gave to stang some to get home qwick time. i was doing about 95mhp after i took my foot off the gas i herd some really bad virbration noise/ rumbling noise coming from under the car. even when i looked in the rear view mirror i could see the rear spoiler vibrating

i took the car to the garage the next day we lifed the stang up to see if any thing was hitting. we checked the exhaust system to see if it was clearing everything that was ok.

the only time the vibration would happon is at high speed and only when i would take my foot off the gas at high speed and we did check the tires are balanced and there ok as well

+ im starting to think now maybe when i had a dyno run they did strap the rear of the car on the right side of the axel but im sure it cant bend it that easy. can it ?


any ideas people ??????????????????????
thanks

2005 mustang GT auto
Stoptech gt stage 2 braking system
Kenny brown strut tower brace
Bmr rear swaybar
Bmr lower rear control arms
eibach pro kit springs
Bbk airfilter kit
Bbk ceramic short headers
Magnaflow x pipe with racing cats
Magnaflow Cat-Back Exhaust System
Bbk 62mm twin throttle body
Moto blue under drive pulley kit
brentspeed Sct tuner
Ford racing 4.10 gears
Comp cam racing cams stage1
comp cam valve steel retainers
comp cam valve springs
Ford racing cmcv delete kit
tci torque converter 3000stall

scottfree said:

I had a toyota supra that happened to once. It turned out to be the center bearing on the driveshaft. Not sure but I think the stang has a similar design.

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it mite be one off the bearings on the driveshaft didnt think of that + im starting to think now maybe when i had a dyno run they did strap the rear of the car on the right side of the axel but im sure it cant bend it that easy. can it ?