Search and read many posts. I have a vibration in my car ('07 Base sedan) at speeds greater than 30 or 40. It feels like it's in the drivetrain somewhere. Tires are new Michelins and balanced, brake pads/rotors front and rear are new (vibration better than before all this but still there). Took to dealer Monday and they looked at the suspension and said it looked fine - mechanic said it was normal for the car??

Essentially the vibration occurs at speed and worsens when you let off the throttle. No vibration in the steering wheel.

I'm thinking drive shaft but seems unlikely for car with only 50k miles, although it apparently was hit in the rear at some point.

Any thoughts would be appreciated.

 

That's total (and typical) BS for the dealership mechanic to say that it is normal for the car. The fact that your car was hit in the rear adds a whole extra layer of suspects to eliminate though. I agree with your instinct about it being driveline related since it changes noticeably between accel and decel. Besides the usual suspects, I'd also look at your engine, tranny, and diff mounts, as well as all the U-joints and the center bearing.

.02

 

Ya if you can't feel it in the wheel then you are probably looking in the right spot (rear). Get that *** end thoroughly looked at.

 

Thanks. Forgot about the mounts. Guess I'll check them next time I do an oil change or whenever I get time to put it up. I know the diff bushings are fluid filled so that one should be easy to check.

For the drive shaft, it looks like the center support is replaceable but not the U-joints. Man, I don't want to guess wrong since it looks like a new drive shaft is $600. Even the center bearing is $200. I guess I could try the cheap fix and try a used one and see if any different. Ebay has one from a car with 56k for $90. Looks like a simple bolt on/off.

 

Yeah, will look at the diff. The car aligns perfectly though so I don't think anything is bent.

 

Did you have this vibration before you put on the Michelins and did the brakes? Tire stores need to have their balance machines calibrated at least once a year! Is it possible your issue could still be a balance problem? You may have lost a weight...have it rechecked!
Gary

 

Yes, had the vibration before the new tires (cheap Sumitomo's that I was told previously had runout) and brakes. Tire place balanced them and the dealership actually balanced them again to see if any improvement (one wheel apparently had no weight on it at all). So the vibration from the wheels are gone but not the drivetrain. Hard to explain but I can feel that the wheels/tires are okay. I must say that I love the Michelins - glad I sprung the extra $$$ for them.

 

Well I had little vibration and the day I wanted to get a new Carbon fiber driveshaft they were test fitting it on my car for the final connection to be made. They told me my OEM was bad. Went back to the dealership and told them that I had little vibration in the driveshaft and replaced it for a brand new one. Went back to get my CF driveshaft and now the new OEM one sits under my bed. They told me it's pretty common for these to go out. A lot of ppl just don't know that they are bad. Oh I got mine replaced just a little over 50k miles.

 

I'm not even sure how you tell if it's bad.

 

When you drop the driveshaft and the joints are not smooth when moving them (has a little click), then it's bad.

 

Took the car to another mechanic (local) who drove the car at various speeds including releasing the throttle and he said he couldn't feel anything. He looked over the suspension front/rear and said the u-joints looked okay. The car has an aftermarket exhaust and apparently they welded new posts in couple of spots - may that's what I am feeling?

Either these guys don't know what to look for or I am overly sensitive to vibrations.

 

well, after that, do you still have vibration?

 

Yep, still there. Had a long interstate drive today so tried some different things. If the car has the vibration and I take it out of gear it's still there. If still coasting and vibration, revving the engine doesn't change it.

I'll put it up on ramps tomorrow and see if any of the bushings look worn or dried out. Car is from Houston and appears to have stayed outside a lot so maybe just the rubber parts going bad.

 

Update - replaced the driveshaft and most of the issue went away. May try to take to wheel repair shop and have them check the wheels. My experience with wheel shops is that they'll tell you every wheel is out of round and then you have to figure out if it's significant or not. Any tips with this would be appreciated.

 

I still have the original driveshaft so I checked it out. The joints click when they are pointing straight/level. Also, the bearing for some reason didn't look entirely round. The flex disk at the end looked okay though.