Hi,

I went and checked heights on two sedans and a wagon. I get anywhere around up to 26” as an average to be fairly normal.
I have rear springs used on mid eighties wagons under all my sedans. It can make the rear end set up to one inch higher. I got the idea from my 1978 GT that’s a factory Setup to be tilted higher in the rear.
Original sedan springs do weaken or settle downward losing strength support that I have not noticed on the GT.
Most likely a different specification.
On the standard sedans a moderate load to squish them far sooner and car looks ugly. IMHO.
Adding luggage or passengers made it non-acceptable to me.
My first experiment was with IPD overloads under a sedan but they are too harsh for an empty trunk.
They went onto my 86’ wagon and those springs from there helped the sedan feel more normal.
The wagon now hops up a little extra on the speed humps when empty but I can stuff up that sucker even better. (:)

I run the 195s mostly now as they are a more popular size from Costco than the 185.
Either sizes are not carried in the stores but available from their distributors within a couple of days by ordering.
As far as I know this is so nationwide within the Michelin brand. Don’t know about Bridgestone.

I also have one car with the 185-70 and others in 195-70s. Both are Manufactured in 2015 and are the Defenders
My wagon has the older tires of the “X” radial style of 195-75 profile.
I wonder if I have seen the last of the 195-75s. I might have to run a 205-60 or 70’s to keep road height and load capacity as designed.
I once had 205s on a sedan and the car was quieter and somewhat more stable with likewise same air pressures as my other tires.
Tire carcasses vary wildly with aging and I have better longevity and less air loss with Michelins.

You might consider that the tires are questionable in your case on the car since it’s a speed resonance thing.
You have told us many variable factors that the car actually bopping up and down.
Have you tried putting BB’s inside a clear glass dish or jar.
You should see how they react to the floor or seats.
If you driving an airplane 😳I’d say hang a pencil on a string from the ceiling to make sure you are not upside down.🙄
My scan tools are cheap but microphones or cameras under the car might be next.

Move the jar around inside the car and see if they are truly jumping or bouncing up and down and not rolling like they ought too.
The passenger seat can create a noise if it’s not sat in.
The back can shake if not left snug in a direction or worn.

Tired carcasses of aged tires or a slipped belt(s) are factors in ride and noise. The front end floats or is more reactionary than the rear axle. More like having two independent girlfriends. 🫣

A belt bulge or a knot is another resonance thing.
Remember all rolling tires become flattened on one side and can “stay flat” on one side if no longer rolling long enough. 🤪(:-)

I’m thinking that all tires sizes are suffering from shrink-inflation and have for quite sometime now. IMO.
With the introduction of more and more foreign tire makers under our DOT regulations the market is wide open to to quality issues along the lines of longevity.
What’s fine for a couple years slowly gets bad enough to notice.
Use to be with tires and batteries you received in accordance of with what you paid for them.


I don’t think oatmeal stiffness is what you are inferring here but maybe the front struts having stiffness.
You lost me there.
I assume you are referencing the strut inserts. Are your tires running round without dimples or waves in the top of the tread blocks? They should be smooth with no golfer divots.
I’m trying to imagine your testing procedure but reading the tires wear is best.
Wouldn’t you have to have the insert out from under the cars springs to hear or feel the hydraulics setup.

I can only see a spoon in oatmeal so it still leaves me lost.

You are keeping this interesting I’ll give you that.
I thought you had the driveline shop work on this before?

Phil

Hi,

I will have to say things are sounding very weird here.

You said the shaft seems to bent at the splines.
That makes it even more interesting as that it is an assembly made to compensate for the rise and fall of the axle.
I’m sure they must align smoothly as they do go back together greased.
It might be possible that bend is causing a flopping instead of an out of balance.
I spoke to the ends of the shaft not running parallel but blew it off as all is rubber mounted under the car.

How badly does it run out? Was it by sight or measured with a dial indicator. They should have told you the amount. By sight they should have stopped right there and not try to balance it, IMHO.

It’s one thing to be out of balance of weight but trueness is another issue.
The lopsided motion tied in with joints allows the mass to move up and down the axis rotating member.

I know it’s hard to imagine but the closest thing that I can describe it to be is like trying to spin a rope from one end to the other and then putting a drag on the other end.
The rope tends to bunch up and then release it’s stress along it’s axis.
The twisting effect moves and no balancing of any one area can compensate it away. At various speeds it becomes compounded dynamically.
Balancing deals with fixed densities and therefore fixed weights work.
There are such things as semi-fluid weights used to help FWDS front wheels and some commercial appliances but that’s leaning towards some exotic applications and induced harmonics.
I think that’s what you are referring or trying explain how the vibrations are changing.
This might explain the occasional vibrations coming and going with road surface changes let alone variations in torque.

Do you have something loose inside the car thats a tell? The upright portion of a passenger’s front seat is one good indicator.


When you keep mentioning the front end struts affecting the rear shocks?
There are the rear torque supports rods and then the panhard rod that goes across the rear axle.
It is seldom a problem but controls the twisting side to side up of the axle up under the body, but then so do the trailing arms and shocks.

So, This is where I’m lost as this is a 700 and not a 240. I’m truly a fish out of its pond!

The thought has jumped, like a fish in my mind, that you might have a bent rim and you are moving the wheels. Especially, around while changing axles.
This could be adding more weirdness to either the front end or the rear of the car.
I keep thinking the vibration must be rather severe for you to keep picking up on it.

This is just a “feeling” I have towards the 700 series body.
It was a rendition style to grab some of GM’s customers, yet at the same time, may have picked up on Chrysler’s K body as way of doing experiments.
I can remember hearing about Nivomat suspension systems being a mess.
Did your car start out that way?

Sure hope you find the weirdness as this is interesting!

Phil

To clarify, so far we have:

New engine and transmission mounts plus used (about 40k miles) KYB Gas-A-Just Shocks on the rear
--Vibration started.
--New universal joints, carrier bearing, and carrier bearing support.
--New metal on metal noise started (failed bearing inside rear end)
--Installed used whole axle
--Still vibrating at particular highway speeds, but only occasionally
--Shaft balanced (some weights are huge, was told the shaft was bent near the splines)
--Vibration different but still definitely present


Ideas
? Bad front struts causing weird angle in the rear pinion
? Bad/worn rear torsion rod bushings (or poorly installed since I did it in a rush and tightened them with the car in the air) causing bad angle on the rear pinion
? Bad tailshaft bushing - lots of oil on the transmission, but seems like it is engine oil and not trans fluid

Hi,

I’m not familiar with the 700’s driveshaft as I have only 240s.

I have to say that it’s unusual to see that many weights stuck onto a driveshaft to begin with.

From that scene I’m visualizing it appears that someone was trying to balance it and that didn’t know what the heck they were doing after it left the factory.

In the factory, each length of tube is made to its required length with a trimmed in bore made to make both outsides or insides too make it run rather true.
All mechanical tubing can have lopsided areas of density. Side to side and from end to end shifting in rotation about an axis. That’s call resonated shifting.
Similar too two planes of balancing in our tires and the rims. The Old Bubble balance is only in one plane technically.

On tubing Some small amount run out is inevitable from end to end and there’s always a density issue.
Between these two it is what makes it out of balance.
A small amount of either gets compounded with radius from center and speed of two forces, centrifugal and centripetal from end to end of each section.
Drivelines change in driving angles of motion, so balancing is a must.
Most tubes are made within a certain wall thickness tolerance so it’s not that much or should be?
Each piece is put pit on spud ends ends by plugs or caps that have a center hole to hold the shafts in a balancer.
It is then spun by a semi rigid drive to locate the shafts in a plane in a relation to the end supports and the driving head.
Sensors in the supports and in the driving head read and oscillation movement from a zero plane of calibration.
Removing metal or a adding weight are the options.
If it’s a lot the metal needed to be removed, do it first.
Within that, It all depends on an items structural integrity and ease of doing an adjustment.

Having whole bunch of weights added is not a good thing, for the most part.
Production facilities runs batches at a time. Most metal stock can have traits develop as numerous variations. Us humans know this so they see trends and adjust for them quite well.
Having an aware and skilled workforce paying extra attention can be expedient in most aspects of production.
Even today, Not everything can or should be, run by num nuts.
Even Artificial Intelligence machinery will be needing some of the “real stuff” to make up for its errors.

All those weights bother me as you can see, as it’s a tell that something must be wrong.
So if that was what was under the car and you lost a significant weight or got it out of phase, this is what happens.
You also do not want a stiff joint in one axis plane as it will affect the balance or even the readings on the machine for sure. How much in a car with an unknown active suspension is a tough call.
Don’t be surprised if they decide to change a universal joint. At least you are aware of that going in!

Was this car wrecked or had things changed or modified?
Maybe it got tweaked in a sudden load change?
Is it really rusty outside or in like ever been submerged or struck from underneath?
If so, the weights are saying, this baby, has been worked on.

Remember what I said, that a dynamic balancer using a semi-ridged drive coupler as they do not want the driving head bearings to impart any fluctuations into the scheme.
If the newly balanced shaft with hardly any weights, This is saying they did a good job and they salvaged it.
If you still have the problem Get suspicious towards the other ends of the car suspension or a transmission mount resonating. Very unique if it’s that from my standpoint.

Keep us in the loop.

Phil

Hi Will

That's quite an ordeal over there.

Do you think those are the original hex bolts on the flange?
You'd think that it would be designed to be easy to assemble at the factory.

How did the problem start? Did some driveshaft weights get lost?

Happy holidays, Bill

Yes.... but I jacked up the driver side to do it and I think that may have hidden it. I had a small shop show me exactly what that looked like before, and it was awful. I was about to order one without checking, but I did check. This one seems tight.

Negative, not the tires. The driveshaft can be mounted in a machine and balanced It's done when they're new, but after 230k miles plus new universal joints, a bearing, and me not being too nice with it, it probably needs that redone. Shops weld weights onto them in the process and can even straighten them with heat and a spot weld.

Another factor whenit comes to th driveshaft is the "clocking" of the U-joints. That becomes an issue if the driveshaft halves are not reinstalled in their original (as manufactured) positions. By "clocking" I mean this--If the first flange attached to the transmission has its loops horizontal to the ground--the rear most flange (attached to the diff) has to have its loops vertical to the ground--in other words --imagine the front flange and rear most flange aligned together they would form a comlpleted U-joint. Of course--that alignmment can be attained with one half also rotated 180 degrees. But only one of those 2 positions will be correct for balance. Having worked on rear drive Volvos for neasrly 50 years I've never heard of shimming the center support bearing. If the angle has changed (at the rear) that could only happen if the springs are severely worn out. The rear can tolerate un-ideal angles such as having rear seat passengers or heavy things in the trunk. if the angle of the front half has changed the fault has to be motor/tranny mounts. - Dave