Funky Chicken...er....vibration

[oldmako]

Genamins, You regulars (and you irregulars) will recall that I recently jumped in the Y33 wheel bearing post due to a slight vibration in the seat of me britches and the steering wheel.

I think my car has a slightly different ailment. What I was able to determine today (through some fairly sporty and aggressive driving) is that the vibration is MOST prevalent during acceleration / load at speeds above about 77mph. If I stomp on it pretty good at that speed I can feel it, and if I lift off the pedal it almost disappears.

Now, that's not to say that I don't also have wheel issues, but this makes me think either drive shaft or rear trans mount. What says you??

I am unable to bring up anything using the search function vis a vis the transmission mount, although I do recall it as being somewhat prone to failure and a cause for vibrations. I will peruse the FSM and try and get my learn on with regard to this mofo.

My queries to the great Qmasses are.....Am I smokin' crack thinking it might be the trans mount? Is that mofo relatively easy to replace?

I read so many horror stories (here) regarding replacement drive shafts never being right that I want to avoid that item. Plus, that sumb**** is expensive! When it falls out I'll junk the car.

And ahh let's see.....I have never replaced, greased, torqued, tweaked, fondled, lubed, stroked or manipulated the trans mount. Ditto for the drive shaft. There's the detailed maintenance history.

Flame away.
Modified by oldmako at 4:04 PM 11/16/2009

[Mopar]

Does your shifter vibrate or move also?

I would say it's your tension rods going bad.

[oldmako]

Shifter is totally fine and rigid. Tension rods were replaced two years and 49000 miles ago. Methinks it's elsewhere. It rears it's ugly head under load, which points to the rear end or drive train.

[maxnix]

I assure you the tension rod bearings are well beyond their life unless you are numb from the waist down.

[goody90q45]

Brian's up to speed again.

[paranoidjack]

I still stand on my original recommendation of changing tires, or at least swapping them, and carefully watching for the issue following the tires.

Usually, balancing/alignment/runout issues are most prevalent at high speed. Bad tension rods (although probably also needing love) are easily diagnosable at lower speeds, and in fact are MORE noticeable at low city driving, when the car's weight is shifting left right, back and forth.

[oldmako]

Perhaps you are all correct.

However, I find it hard to believe that a car driven just 49,000 miles ( 99% of which occurred on the interstate) has bad tension rod bushings after just 21 months of use. They appear fine and show no leakage, which has been repeatedly touted as the harbinger of death for them. When I bought the car they were shot and leaked like sieves, yet the car had no outward vibration like it has now. So, this diagnosis makes no sense to me. How often do you replace your TR bushings?

Would they not most clearly signal failure during decelerating turns when they are under the highest load? And again as the car is unweighted coming out of a turn?

The car is darn near astro-glide smooth until I mash the accelerator at high speed. To my mind, a bad tire at 80 mph is going to manifest itself at all times above a certain speed, whether the car is accelerating or coasting. Yet, the vibration stops the instant the accelerator pedal is lifted. The tires require almost no weight to balance even after 45K and barely show an out of balance condition when initially mounted on the machine with the old weights still in place.

If it's the bushings, great! They're cheap and easy to replace. New tires will be fitted in the spring.

But the skeptic in me says something else a bit more sinister. I hope that you are right.

Should I stumble across it, I will surely add it to this post.


Modified by oldmako at 6:08 PM 11/17/2009

[maxnix]

It's age, ozone, UV, water, salt, time and everything that starts to degrade the rubber. Just because they aren't busted open doesn't mean they are working as intended. You just can't load them like the car does when it is dynamically moving. Keep a very close eye on them because if they are not at the end, they are very near.

If it is drivetrain slop, it should likewise occur at any speed (loading is what is relevant, how much and in which vectors).