I'm posting this here so I will have a decent idea of where to start looking.

I suppose I never noticed this before because the only time I exceed 70MPH is during WOT test/datalog runs.

Yesterday I traveled with a couple co-workers to the world cup finals at MIR. We took the scenic route down the interstate and through alot of backroads with cruising speeds sometimes creeping towards 100MPH.

Around 75 - 80MPH+, I get a very disconcerting pulsing (NOT steady) vibration throughout the whole car. It's so strong you get the feeling that the car is going to fall into 1000 pieces at any given moment. You can even feel it in your ears that's how strong it is. I get the same pulsing in the 60 - 70MPH range but it is so subtle that I never thought it to be a problem. Below 60 it is practically non-existant.

The last time I checked my U-Joints was a couple months ago and they all seemed fine. I have done lots of datalogging since WOT shifting into 4th gear and made a few passes down the track however I don't hear any strange clunking and knocking noises on decel/takeoff so they aren't my first concern although I know I should be checking them again.

My question is is this considered normal for a stock steel driveshaft? I have read that they are famous for the pulsing vibration problem and was wondering if upgrading to an aluminum piece would fix this issue? The car has also recently been lowered I figured I'd mention that as well since I know it changes the pinion/driveshaft angle and introduces more stress on the U-Joints.

Thanks guys.

 

Sounds like tires to me. I know when im doin 70 cause the car will shake BADLY. My tires are unbalanced.

 

It's quite possible. Aren't you supposed to get a rebalance if the tires have been patched/plugged?

I've had to plug both my back tires due to nails.

But then again wouldn't an unbalanced tire cause a steady vibration vs a pulse?

 

I work at a tire shop this happens a lot my room mate has the same issue its due to unbalanced wheels and if they patch your tire they can just mark the valve and remove the tire sometimes if they don't pay attention they can wack the hammer on weights if you have any sometimes there's sticky weights and if the rim isn't cleaned and is dirty weights can fall off and rear tires can be static balanced so they may only be weights on the inner side of the rim hope this helps also if you have two different treads on a axle front or back can cause vibrations make sure tire sizes match in pairs eg 245/40r18 and not one 245/45r18 and a 255/35r18 some cheap or scam shops try this any hope the customer doesn't notice usually they do and go somewhere else again hope this helps



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My old tires did that once I hit 70 MPH. It would ride fine, and as soon as you hit 70 it's noticable. 90 MPH and it's bad. So glad I'm getting new tires soon, heh.

 

Just to confirm, you were getting a pulsing vibration and not a steady solid vibration?

 

Front tires are a pair of Kuhmo Ecsta ASX 225/60r15 and back tires are NT555R 275/50r16. All 4 wheels are static balanced with stick on weights on the inside of the wheel.

The tires that had nails in them I pulled the whole wheel off myself and used the oldschool style plugs to repair.

 

You could say that, yeah. You could start to hear it slightly at 50-60 MPH, but it was minor.. but once you started hitting around 70 MPH it got much louder and you could really feel it. It definitely wasn't a steady solid vibration because it was perfectly fine at 50 and below and not noticable at all.

 

About the same problem I'm having. Very disturbing feeling. Like the whole car is about to fall apart.

 

About the same problem I'm having. Very disturbing feeling. Like the whole car is about to fall apart.

 

Yeah, it's dangerous once you get up to about 100 MPH. I did that one time and I actually remember the last time I did it (because I incidentally only went that fast once in this car).. definitely not an experience I intend to have again because it feels like something is about to break loose and send you flying into a guard rail.

 

Got this out of the Service Manual for diagnosing Vibration issues.
1. Tire or wheel out of balance
2. Loose wheel bearings
3. Worn linkage pivots
4. Worn ball joints
5. Excessie wheel run out
6. Blister or bump on tire
7. Prop Shaft unbalance

I went thru this on my car. Balanced the steel prop and still had issues. Went to the alum prop and while still not perfect, much improved. I would folllow this flow chart to rule items out before going the alum prop shaft route.

 

Even though you say you "checked" your U-joints, don't rule them out. I don't know how you checked them, bu just getting under the vehicle and tugging at the drive shaft is not a check; you'll only feel something if one is practically falling apart.
If you have an otherwise quiet vehicle, you can sometimes hear a clicking/popping under load or squeaking from one that is starting to go. The only sure way is to remove the driveshaft and inspect them for smooth and free movement.

 

Duly noted.

I've actually been wanting to do the aluminum shaft upgrade as soon as I find one in the yard. It isn't on my list as just a problem solver piece.

My friend has a 1LE shaft he'll sell me for 100 bones, which wouldn't be a bad deal if it didn't have a plethora of deep scratches circling the entire diameter.

 

my car has the exact same isuue at the exact same speed, i got a balanced aluminum drive shaft from jegs and new u joints but it still shakes. I noticed though my panhard bar is bent, assuming the po curb slapped it at some point. I was told that i may have a bent rim or worse, bent axle shaft. I just never go over 68 so i haven't pin pointed it yet. let us know if you get it figured out.

 

I've got the same problem with my car at 70 mph. Could it be bad wheel bearings?

Chuck

 

If its front suspension/wheel bearing related you should also feel it in the steering wheel and that would act more like a shimmy,lol, turning hard would feel akward.

 

As long as you have same tread pattern on the same axle its OK I hate static balance on the front its fine for the rears but you can still do a regular and more accurate balance with stickie weights on the inner and out lip inside the rim there's usually a indent or raised lip for the sticky weights and make you wheels clean first because 80% of the time buddy is lazy and they fall off when you drive away

 

New theory on the vibration at 70+ mph.

A while back I noticed that my air dam is severely damaged. Didn't think much of it but on further inspection, the part that survived, appears to be loose and has a tendency to wobble.

Might just be as simple as an aerodynamic turbulence issue...

I plan on removing the piece when I get a chance and I will report my findings after a
High speed flight regime test...hehe