05slpGT

Ive seen this problem posted a few times but found no solution for mine. Ive been battling highway vibrations for a looong time now. Ive had my shocks, struts, springs, driveshaft (shaftmasters), and rear end (boss 302/gt500 rear end w/ 3.73s) all replaced within the year(driveshaft is about 2 years old) and this problem is still happening. It changes when it starts too. Sometimes on road trips it will feel like the car is going to explode at 80-85, other days it wont be bad until 100-110. Has anyone heard of this problem and have any idea what it could be? brakes? transmission? i have 89k on the car stock clutch but i dont see that being the problem... upper/lower control arms?do i need to get to get adjustable control arms? I am lowered, but only by an inch, and steeda said id be fine when i bought the springs. No shop will test my car at that high of a speed, so its making it a difficult problem to fix.

danzcool

With all you've done, you didn't mention the obvious first check on vibration, I'm sure you've checked, but I have to ask, have you had your wheels balanced?

Boss_Hotrod

Exactly what I was thinking. Get them road-force balanced. Tire balance will do some strange stuff.

ClayBonics

My thoughts exactly Road Force Balance makes all the difference.

05slpGT

Yeah, I have but its been a while, I'll have it checked on monday. Havent heard of Road Force Balance, if its different than a normal tire balance, where would I go that would have one.

tdbrown75

I have the exact same problem only mine starts consistently at 80MPH with 4.10s. I’m lowered with Steeda ultralites and run the FRPP dampers. Never had any problems with the stock 3.31s, mine started when I went to 4.10s. Since the vibration developed I’ve had several sets of gears, tried adjusting the suspension geometry and pinion angle with an adjustable UCA and pan hard bar, and even replaced the entire axle assembly. After all this I’ve done nothing but managed to move the vibration around between about 65 and 80MPH.

Mine is a resonance type vibration with a bass sound, definitely in the driveline (too high frequency to be a wheel/tire and anyway I tried swapping those too). It’s spent weeks at the local dealership with NVH sensors and analytics software trying to isolate the vibration on a Dyno. Attempts to weight the driveshaft made no difference just like the wheels, adjustable upper and pan hard bar and new axle.

At this stage I am convinced the installer (master Ford mechanic) at the dealer maybe wasn’t that great with gears. Over the last year they have developed a whine on decel and a booming resonance around 40mph in addition to the vibe over 80. I hate it and it makes it hard to enjoy the car. The 4.10 RPMs on the highway are too much for me so I’m taking it in one last time for a set of 3.73s at a trusted speed shop to give it one more shot.

I’ve learned lots of things as I’ve gone through this experience but one stands out above the rest. DON’T MESS WITH GEARS IN YOUR S197 MUSTANG!

Tim

05slpGT

Sounds like the same kind of vibration from the way you described it, only difference is i am getting no gear whine at all, and on my old rear end i had 4.10s and they used to howl. But i dont think mine could have been gear install, the rear end i bought came fully assembled. It is so damn frustrating and your right, makes it hard to enjoy the car.

tdbrown75

At what point did you notice it exactly? Was it after a particular mod or just something you picked up along the way? I'm fairly certain mine started after my second set of 4.10s which is why I suspect gears. I drove it lowered with the 3.31s for years and never had a problem. I suppose it could be coincidence or maybe they jacked something else up while back there. I too am at a total loss at this point. I thought maybe brakes a one point myself, your brakes stock or you have mods? I'm running drilled/slotted rotors from Rotorpro's.

Tim

drfister

When I initially had my driveshaft and 3.73s put in, I had a bad vibration while cruising on the highway at 130km/h (80mph). This was on top of gear whine with richmond gears. Auto trans, Steeda d/s (not sure which company acutally made it at that time, but its the tapered on 4"->3.5"), lowered with pro-kit, had an adj UCA at the time as well. I would get a vibration at ~130-140km/h (80-90mph), nothing above or below that. It was very disheartening because I bought the 1-piece shaft to ensure I had NO vibrations, but it seemed to vibrate when the stock one did not.

Needless to say, I enventually had my richmond gears replaced with frpp gears, still 3.73s, as well as installed a BMR adj panhard bar. The gears and panhard eliminated my gear whine and also suprisingly, and to my great relief, got rid of my scary driveshaft vibration. Smooth as silk. Good luck on getting it sorted out!

05slpGT

Funny... I have drilled/slotted rotors from Rotorpros... how long have you been running them? Ive been running mine for a few years, long enough to be on my 2nd set. And it was no mod in particular that i can think of, and i even had the vibration with stock 3.55s.