Shaking at high speeds.

I feel some shaking coming from the back of the car when on the highway. I just installed new tires and the shake was there both before and after. I watched the wheels get balanced and asked the tech to check if any rims were bent. He said the numbers would not be this good if any rims were bent. anything in particular on the rear suspension I should look at in particular? Maybe the bushings are original and 20 years old on a really rusted bottom.

You have to get it in the air and shake/spin/twist parts to find the cause.

I replaced all my rear end bushings (at about 175K miles I think) just because. Not sure I needed to - they don't take a flogging on this car like they do on say a GM minivan or an Audi.

That's exactly what I'm going to do, I was just curious if they were any usual suspects.

carguy8888 wrote:

That's exactly what I'm going to do, I was just curious if they were any usual suspects.

I am not aware of any for the rears, except for wheel balance, bad shocks, bushings.

I guess I should hope for bushings or maybe a u joint?

carguy8888 wrote:

I guess I should hope for bushings or maybe a u joint?

No.

You're throwing darts talking about u-joints, there are *none*.

Again - you have to get it in the air and shake/spin/twist parts to find the cause. You may find perusing the FAQs and how-to's useful. FOr instance it coul be a wheel bearing BUT the ABS sensors are integrated into the bearings and they usually act up well, well before the bearing is that shot. And if you don't get crap rear wheel bearings to begin with, they will last well over 100,000 miles.

Also, the factory manual has a pretty good section on fixing NVH (noise, vibration, harshness) problems although it often uses a funky tester (which you don't need all that much if you actually read the section). Point is, if you don't have the factory manual for your car yet, get a set.

I do have my owners manual but I absolutely will get it on a lift.

carguy8888 wrote:

... He said the numbers would not be this good if any rims were bent.

That's not quite true. Technically, any solid object can be balanced - a brick, for example.
In practical terms it means that even perfectly balanced wheel can cause vibrations.

DeepFrozen wrote:

carguy8888 wrote:

... He said the numbers would not be this good if any rims were bent.

That's not quite true. Technically, any solid object can be balanced - a brick, for example.
In practical terms it means that even perfectly balanced wheel can cause vibrations.

+1 that. The Riv likes tires that are actually round... my Continental was much more tolerant of tires than the Riviera is. Hands down.

Here's some light reading for everyone - one shop's opinion:

https://www.souzastireservice.com/tires-101/shakes-and-wobbles.aspx

It certainly could need to be rebalanced, I'm going to try and stop by my shop tomorrow after work and see if they can throw it on the lift.

My trusted really good mechanic went through the whole car and found nothing wrong, glad he was honest. I guess I'll try rebalancing the wheels.

Did the re-balancing solve your problem?

On the second round oh, another mechanic found my right rear wheel is a little bent.

carguy8888 wrote:

I do have my owners manual but I absolutely will get it on a lift.

The repair manual, not the owner manual.

carguy8888 wrote:

On the second round oh, another mechanic found my right rear wheel is a little bent.

Would you like to buy a set of Factory Service Manuals for a 99 Riv in like new condition for half of what I paid for them.?
I bought them for a previous member of this forum and after I bought them for him he disappeared.
Anyway, Very Good condition for $25.00 plus shipping. Books are cheap to ship via USPS.
Let me know.
Rick

That sucks, fortunately I'm smart enough to know I'm not handy LOL. I live in New York City so there's nowhere for me to do it anyway. Thank you very much for the offer.

Mine does the same thing but only between 65 and 70 mph. Nothing below or above that speed.

carguy8888 wrote:

That sucks, fortunately I'm smart enough to know I'm not handy LOL. I live in New York City so there's nowhere for me to do it anyway. Thank you very much for the offer.

At that price, what you do is buy the manuals then leave them in the trunk when your car is in for service -- there is enough esoteric about the Riv that the mechanic will be able to do a better job if you have them than if you don't because the syndicated data sources skimp on details, although they are better than they used to be.

stan wrote:

Mine does the same thing but only between 65 and 70 mph. Nothing below or above that speed.

My car is in the shop today for exactly that problem, we narrowed it down to the CV joints (most likely inners) on the left front axle. (I also suspect the inner tie rods but those supposedly are good. Rack is seeping though). My left axle is *original* Saginaw with 370,000+ miles on it. The vibration is a PITA. When you apply brakes the vibration goes away (so it's not wheel/brake). Checked round and runout, both quite good. No evidence of belt or carcass issues on tires. Alignment good.

albertj wrote:

stan wrote:

Mine does the same thing but only between 65 and 70 mph. Nothing below or above that speed.

My car is in the shop today for exactly that problem, we narrowed it down to the CV joints (most likely inners)  on the left front axle. (I also suspect the inner tie rods but those supposedly are good.  Rack is seeping though).  My left axle is *original* Saginaw with 370,000+ miles on it.  The vibration is a PITA.  When you apply brakes the vibration goes away (so it's not wheel/brake).  Checked round and runout, both quite good.  No evidence of belt or carcass issues on tires.  Alignment good.

Those miles, that is amazing.

Car's back, shaking's gone. Road Trip time.

Your only shaking at High Speeds, Dang, I've been shaking at all speeds lately.

Well Albert, don't leave us hanging. Was it the CV joint and axle assembly as you suspected.

I have to agree with carguy8888, it is amazing the number of miles you have on your car. It's a testament to your personnal preventive maintenance program.

If I had continued with the income I was used to getting, I'd still have my Riv, but I fell behind on the rust and rot issues then the paint was gone to the point that I would have needed a complete paint job.

There was a period of time that I not only was able to do the PM items but I would bring it to my body shop just about every year for some kind of sanding, priming and painting with PPG paint. They weren't cheap but they were good, actually excellent. Never saw a flaw in their work.

I know you have mentioned that you have a body shop that you bring your car to periodically to keep up with the appearance and you always keep up with the mechanical issues.
So, I guess it's no surprise that your Riv is still going strong after 300K miles.

The axle contributed some; tires contributed some but it was really subtle; also probably contributing was a stupid problem with the steering rack (slightly loose mount bolt).

Well, after giving this some more thought I would be writing GM a letter and complaining that my front axle only lasted 370,000 miles on my 20 year old Riviera and what are you going to do about it before I get the legal dept involved.

Nice lol.