Thread: Chassis Vibration Help

The chassis will vibrate (not the steering wheel) from about 40-75 MPH, possibly a more narrow speed range, but you get the idea. It shows up randomly, doesn't show up constantly, and I can't do anything special to replicate it (i.e. accellerate, turn). It feels like the vibration is lessened the higher the speed gets, but nothing changes with the RPMs (up or down).

The car has 85xxx miles on it and is not lowered. I have had the dog bones flipped longer than the vibration has been there. I just rebalanced/rotated the tires and it took some of it away. I also replaced the front driver side hub (nice timkken unit!!) b/c I have been told it was worn by several shops, but that wasn't replaced due to the vibration, nor did it help/hurt (as expected).

I have done some reading, but can't find anything with my same symptoms. It seems like the CV axle(s) would be the problem if the vibration was only during acceleration or turning, but that's not the case. I'm just confused and don't want to just throw parts at it.

THANKS!

Originally Posted by unzip2000

as i feel you have the problem with the rear end wheels since you can only feel it to the chassis nd not the steering. i too had it in my 08 grand prix when i hit 90miles/h the chassis vibrates.
1. check for damages in the rear wheels. bents etc
2. possibly can be due to a bad tire band in one or both rear tires.

easy check would be just swap the rear wheels to the front end and drive at the same speed and check if u can feel it to the steering. if u find that den its easy to narrow it down its the wheels itself.

my car had a bad banded tire and i also had the same problem in my 05 mazda which had a wheel damage (not visible) and in that it didnt show up for the balancing machine too. it showed that the balancing was fine but when u hit more than 80miles/h it vibrates. so im pretty sure its the tires or a lil wheel damage.

cheers

For this one, before I posted I balanced (RR tire was out of balance by 1.25 and .75, others were pretty close) and rotated them, so the RR became the RF. I crossed the fronts and brought the rears straight forward... I'm used to doing RWD rotations, and realized it's different later, but shouldn't matter that much. Anyways, the balance/rotation helped some, but the vibration is still there.

I did the balancing myself, then took that one wheel/tire to a tire shop and they verified the balance and said everything looked good on that wheel, so it's not bent, and the others looked good when on the balancer. Yes, I've seen a bent rim on the balancer... I can tell the difference.

The tires themselves are getting ready to get replaced. They all have even tire wear, but they are down to 3-4/32nds, so maybe a month or two left. Just in time for winter


As far as Chev1998vrolet's suggenstion of checking the front end, the last couple times I had it in the shop I was told the driver front wheel bearing was wearing out, so that's why I (yes, me) replaced it a couple weeks ago, but that didn't affect the vibration at all. I would assume that if a money hungry mechanic finds a loose wheel bearing, they check for anything else that is wearing out, including steering and suspension components.

I try to do my own work unless I don't have the equipment, or I'm getting it for free. (free oil changes by the dealer I bought it from is where the inspections came from).

Now that I've moved to a different part of the country, perhaps I'll have the local Chevy dealer take a look at it, and see if I can get a free inspection out of it ...

Thanks for the help. I'm half tempted just to buy the new tires sooner to see if that will help anything. I'm just still trying to decide between a few, and where to get em.

THANKS!

Originally Posted by chev1988rolet

pick up the front of the car and put it on jackstands. let both front tires hang freely in the air. from there wiggle each tire side to side and same thing again but with one hand at 6 o clock and other at 12. that should show you whether its wheel bearings, tie rods, or lower ball joint. you can also wiggle the cv joints and see if they feel loose. thats all i could think of checking first aside from alignments.

Alright, just got back from the Chevy dealer. I paid them to $28 change my oil rather than to pay the $75 diagnostic fee.... so they aren't hunting down the vibration, however, I did have the check everything (which they weren't willing to do for free... (greedy #$%^%$#).

Anyways, they didn't find anything out of tolerence on the front end.





So,

Front left hub was replaced, but no change (was already declared bad).
Tires are balanced and rotated, no bent rims. (vibration dampened, but still there)
Front end was inspected by mechanic, no play. (vibration still there since nothing was changed)

Vibration is definately intermitant and doesn't show up every day, but when it does, it's very noticable; definatly not in the steering wheel either.

I have noticed a slight groan, but I can't figure out how to replicate, or what conditions are creating it. Makes me suspect the CV axle, I just don't know how to make sure one is bad. I really don't want to go buy one and put it in just to determine that was not the problem. ..ya know..

I'm just gonna go throw it on a lift and take a look myself. See what I can find.

just got back from the shop and the mechanic was right, everything on the front end is good and tight, no play anywhere (tires 6 and 12, 3 and 9, and cv joints).

I checked out the motor and tranny mounts and they both looked good to me.


...I did find that my exhaust is leaking again, and I keep blowing out the flange gasket between the downpipe and the resonator.... but that's not causing the vibration, just the regular annoying exhaust leak....argh!

both intact, but I did look at them

unbroken, but you know, I didn't think to look at the rear, so I can't really say that... I did notice the endlink bushings are developing small cracks in them and they could probably be replaced. I guess I'll have to check the rear sway bar when the exhaust leak is reparied. I'm expecting the rear sway bar to be intact as my understanding is that one usually doesn't cause any problems.

I'll let you know, hopefully tomorrow! (Saturday)

oh. end links are alright, I can't push/pull on it with the car in the air. everything in the front end is solid.

I'll probably just grab the end links since they are $15 for MOOG and I can get em in town tomorrow

Ok, so, I grabbed my MOOG end links and an exhaust gasket and went to town. The exhaust shops in my little town are worthless... they don't even keep gaskets on hand! ...so it's up to me to fix it right, the 4th time (this one should be properly done!)

What I found was pretty interesting, the center section of the passenger side end link was siezed to the bolt, so after I took the nut off the top, I couldn't get the bolt to come out. After a lot of prying and pulling, I had to put vice grips on the center section and use the air rachet to spin them apart and get them to seperate. I wonder if that was causing most of the vibration, because now it seems to ride much smoother!! Although, it's cornering waaay too soft now, and turn are no longer flat .... kinda miss the flat turning... guess the GMPP sway bar is gonna get put on the list and I'll use the end links that come with that kit.

As far as the exhaust leak, I noticed the patter of exhaust always blowing the bottom of the gasket out. After deep investigation, I realized that there was an old gasket fused to the factory side of the flange and the wire wheel/sandpaper/wire brush combo wasn't having any affect. ...so out comes the grinder!! A few minutes later I have a perfectly flat and smooth, gasketless mounting surface on both sides!!! In went the new gasket (1 of 4 part stores in my town had it, and the exhaust shop didn't either.... this town is pretty small). Well, that should fix that problem, hopefully for good!

Next on the list:

Aeroforce or boost gauge, ported blower/tb.

Alright, so just got back from doing some highway driving and the vibration is still there, but the speeds that it occurs is narrowed and it only occurs from about 55-75 MPH, by the time I hit 80 MPH it's smooth again. Again, no difference in vibration if I'm using the gas and brake pedals or turning. In town (under 55mph) it's generally smooth. Not sure why it does that...

Hmmm, interesting... Here's a silly question- How long after you've been driving does the vibration occur? Obviously on the way back up north last night you had plenty of time for the car to reach full operating temperature, and my thought is that perhaps an output shaft bearing may be generating some of it? It will mimic the vibe one would expect from an inner CV joint, but can be more erratic, temperature dependant, whereas a sloppy cv will usually be consistent. Check your PMs on pclsx, I'll attach a diagram of what I'm thinking.

It doesn't matter what or when, it's just always there.... and never goes away.

That sounds like an inner CV joint... Which is a hell of a lot better than my other explanation.

yeah, much rather spend $75 of the cv joint than get a new transmission!

Perhaps I'll do that this weekend rather than try porting the supercharger.

I'm thinking I need to start a collection of W-body spare parts to store alongside all the Eff body shiz- Other than you, I've rarely had anyone semi-local who would have any use for extra stuff. Sure is nice to have spare stuff sitting aside to work on while you drive the car, minimizes downtime. Figures the cars I don't have to drive daily I have any spare part you can imagine.

yeah.... but unless you are talking about a blower case... I'd rather just get a new axle that way I can keep the lifetime warranty



.... but it'd sure be nice to swap in a new one to check and see if that's the problem....... without buying one first