Roush Holy Vibration!

sal07b · Apr 20, 2007

Well, the SF Connectors are in, but it isn't a good thing at this point. I have a vibration that'll vibrate your fillings out. It is really strange. When I'm on the gas, no vibration. However, as soon as I let off the car vibrates like crazy. The vibration doesn't change if I'm in neutral or the clutch is in. It appears at about 35mph+, and it sucks. Reving the motor-up does nothing, so my thought is that it is not in the motor or clutch. With the car in netural, the rear-end, driveshaft, and transmission gears are turning. Therefore, I guess it has to be in one of those. I find it hard to believe that the car, through the floorboards, would soak-up that much vibration. The only change I made was the addition of the SF connectors, which I know stiffens-up the car considerably.

Sooo.... What now? Anyone else experience a similar problem after installing the SFC's? My thoughts are to replace the drive-shaft with a FRPP aluminum driveshaft. They are supposed to be pretty well balanced. If it's not that, maybe the guys didn't get the back-lashing right when they changed my RE to 4.10's. Thoughts??

s351rspeedster · Apr 20, 2007

sal07b said:
Sooo.... What now?....Thoughts??

...I think it's your paint job?? Change it to a real color and that should cure your vibration!!

....on the real, how about a loose exhaust or broken exhaust hanger. My old 95 S351 had a mild vibration that I heard under the same circumstances that you are describing. Worth taking a look at.....

SVT Saleen · Apr 20, 2007

It is highly unlikely that the subframe connectors would be contributing to the vibration issue. It's probably just a coincidence that the vibration occurred after they were installed.

From your description it definitely sounds like an imbalance in the drivetrain or perhaps as Robert stated a loose connection that is allowing something to contact a portion of the undercarriage of your car.

Take it to a shop with a lift & have it inspected thoroughly for anything loose. If the shop also has a lift where you can stay in the car with it running to attempt to duplicate the circumstances that would be even better.

marcus95 · Apr 20, 2007

I agree.

the vibration you are talking about can't possibly be the subs themselves.

Dave. The cheapest way to find the source of your problem would be to jack up the rear end with jack stands under the axle and repeat your 35 mph run so that someone can visually see what the problem is. Otherwise you are guessing. Just make sure whomever has his head under the car while you have the car in gear is not a good friend or someone you dislike.

TT91 · Apr 20, 2007

put it on jackstands, throw it in gear while running and take a peek, keep your hands away from moving parts.

marcus95 · Apr 21, 2007

Nice.

The short version of what I typed and the disclaimer about it being dangerous.

Saleen87-65 · Apr 21, 2007

I have a vibration at 80mph+ in mine that is awful...i've gotten it narrowed down to either a bent wheel (which is easy on foxes) or an out of wack driveshaft (either out of balance or bad u joints)

I was told you can check bad u joints from merely jacking up the car and shaking the DS to see if there is play in it

marcus95 · Apr 21, 2007

Tim,

I'll bet you $50 bucks it's your driveshaft or ujoints.

It's better than one of your wheels. I have also had a car where the wheel was straight. The guy replaced the wheel but not the axle and it was bent.

Saleen87-65 · Apr 21, 2007

driveshaft would be better imo...i'll just buy one of those nice FMS aluminum d/s' and be done. Guess im gonna find out soon

marcus95 · Apr 23, 2007

My driveshaft in my SSC started to vibrate up throught the car and in the shifter at around 85-95 mph and then the vibration went away around 100mph. It was from sitting for years without being driven. I was going to replace it but sold it before I got a chance. I was sure it was the driveshaft.

Onefine88 · Apr 23, 2007

I'm with you on the driveshaft theory. My SSC had a drivetrain vibration at hwy speeds when I bought the car. The faster I got on the hwy, the worse it got. I bought a FRPP aluminum DS and cured that problem.
I also own an '88GT vert. I Bought it new. It has always had 2.73 gears. During the winter I had them changed for 3.73s. Never really noticed any vibrations before. After the gear swap that car then developed the same vibration on the hwy. I blamed my mechanic for doing something wrong in the rearend.LOL He told me my driveshaft is now spinning alot faster at higher speeds with the new gears. I took the aluminum DS off the SSC and put it on and went for a drive. Smooth as silk. I went and bought another last month for the convertible. "No more vibrations."

Good Luck, RandyP

s351rspeedster · Apr 23, 2007

.....fine!! Take my theory of a loose exhaust hanger and throw it out the window!! Damn, that will teach me to reply to a post first
At least my theory would be a cheap fix if that were the problem!!

281cobra · Apr 23, 2007

marcus95 said:
Tim,

I'll bet you $50 bucks it's your driveshaft or ujoints.

It's better than one of your wheels. I have also had a car where the wheel was straight. The guy replaced the wheel but not the axle and it was bent.

+1

This has happen to me twice. Once with my old 85 GT and once with my 99 Cobra and both times it was the driveshaft.

sal07b · Apr 30, 2007

Thanks for all the replies. I tried to get it on a trailer today to take it to the shop that put in the gears (in case it is the back lashing) and about ripped the front end off I had wood under there (front end was too low), but it broke sending me down on the front facia. It popped loose on the passenger side and cracked the damn paint. I got pissed and put it back in the garage. I guess I need to find a lower friggin trailer, or longer ramps. Either way, I'm not giong to get it done today and now I need to get the *&#ing front clip re-painted. I'm about to sell it and buy something else (not really, just pi$$ed)... Venting

Saleen87-65 · Apr 30, 2007

I put a friends stock driveshaft in my car over the weekend, with alot better u joints then what was in my car...it definitely seemed to smooth things out some, but its not completely gone....I guess that shows me it is in fact the DS, and that I should just buy an alum one

2000xp8 · May 1, 2007

If you have the extra cash, first thing i'd do is just change the driveshaft, the FMS is much better balanced and smoother than any stock shaft.
Even if it doesn't fix the problem you'll at least have the aluminum driveshaft.
My money is on it being the problem anyway, since i've had similar issues.
Also check for the rear shaft bolts being tight, i had one loosen up one time.

saleen065 · May 2, 2007

Another vote for the driveshaft. I replaced mine with the FMS shaft and eliminated the vibration I had at 80mph.

Roush Holy Vibration!

sal07b

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s351rspeedster

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SVT Saleen

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marcus95

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TT91

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