Have We Solved The Steering Vibration On The Freeway?

[CadiJ]

jdavis12 --

You are ALL OVER THIS! My car JUST had the washers installed. I am going to pick up the car now and will let everyone know what I find...

I wonder what this "reprogram" is all about, better not impact my MPG's!

Originally Posted by jdavis12

I picked this up off of the Edmunds forum today:
.....there seems to be a new bulletin out as of yesterday to address the vibration problem. It is #08-07-30-044A: Phasing Drone, Boom, Moan or Vibration at 80 km/h (50 mph) or 1000-1300 RPM with Torque Converter Clutch (TCC) Engaged (Reprogram TCM and Install Insulator Washers [On Vehicles Built Without Washers]) - (Feb 11, 2009). Apparently the insulator washers were part of the later built cars. They have to be added for VIN prior to 90159377

[Jimls]

This is Great!! News...I Hope.
Please post your findings for us to review. If this works I will be making an appt. for this service.
Jim

[DMill]

That's great, jdavis12 ... Good find!
If this IS the solution (CadiJ - Let us know ASAP), then I just may bring buying a new CTS from the back burner to the front!

[CadiJ]

Hello Everyone!

Ok I was really hoping to deliver the silver bullet fix for the vibration issues so many of us are having with our CTS's between 40 MPH and 70 MPH.

I have been trying to get GM to fix my CTS since I picked it up in late November.

The new PIP that was just released for this issue instructs the dealer to install:
F2143 Carrier Assembly (complete) Rear Differential Replace. From my paperwork the part number looks to be:
20827776

From what I was told the regional cadillac engineer and district service manager were the two people who tended to my car.

Here is what I have to report:
It is WORSE

My shudder prior to the new part install was a "slow shudder" starting at 45/50mph. After the part install the shuddeer is now a "fast shudder" starting at 35mph and continues all the way up to at least 80mph as that's the fastest I got the car up to.

I don't understand how on earth the engineers didn't feel this as I felt it within 2 minutes of leaving the dealership.

NOTE: my paperwork states, "Rear axle mount insulators developed by GM engineering to enhance customer satisfaction were installed to ensure optimal performance..."

SO there we have it, the 2008/2009 CTS platform does in fact have a design/engineering/production flaw which contributes to NVH and for me a very noticeable shudder.

Such a shame, the CTS is a beautiful design but just not the car I thought it would be (for me...)

Originally Posted by DMill

That's great, jdavis12 ... Good find!
If this IS the solution (CadiJ - Let us know ASAP), then I just may bring buying a new CTS from the back burner to the front!

[fast400@me.com]

There's a counter weight on the back right side of my rear axle. Mine's a European model. Do the US models have this counterweight? This might be a player in all of this vibration. It's the only reason GM would put a block of weight on a car.

[CadiJ]

I am not sure, anyone know about the weight on the rear axle?

Originally Posted by fast400@me.com

There's a counter weight on the back right side of my rear axle. Mine's a European model. Do the US models have this counterweight? This might be a player in all of this vibration. It's the only reason GM would put a block of weight on a car.

[C "T" ess]

It's a balance weight to balance the shaft. Same theory as adding weights to balance a tire.

[fast400@me.com]

...sounds like a place to start looking for the vibration source. Anytime a car maker adds weights anywhere...it could be the source of imbalance/vibration (they put it there to prevent exactly what is happening...vibration! Since everything else has been looked into...this might be a source. I recommend for someone with the problem to figure out a way to stick some extra weight on to see if it changes the vibration.

[Southern]

Can you post a picture? The rear axle is enclosed and putting a weight on the axle housing, which does not turn, will do.........exactly nothing, IMO.

[fast400@me.com]

The weight is attached to the R rear side, but not directly sitting on the axle. I'll go out and take a pic tomorrow. While I was doing my oil change is the first time I noted the weight (checking everything out while I was waiting for the oil to drain)...trust me, it wouldn't be there if it didn't have a real good reason.

[fast400@me.com]

Here's a pic of the rear axle weight(the black round thing). The other source could be loose shock. Have the shocks been checked?

[Southern]

Looks like the hard rubber bushing used to mount the rear subframe.
The CTS uses a multilink suspension on a rubber isolated sub frame.

[fast400@me.com]

Southern: It's not mounted to anything, except the rear axle. It's metal not rubber. Take a closer look. I'm not talking about the the pieces connected to the subframe here.

[CadiJ]

The vibration is totally drive train related. The service manager would take the car up to speed when the vibration started he would shift it into "N" and there was no vibration. As soon as the car was shifted back into "D" the vibration was back.

The drive train vibration is well known by GM all of their PIP's say, "GM engineering is aware of the problem and is working on a fix..." The bigger problem is that the latest PIP as of this month STILL does not fix this issue and in fact the "fix" that GM did to try and solve the vibration only made matters worse.

[fast400@me.com]

Today I took my CTS to a tire shop here in Germany. The tech was very experienced and noted that they've had some newer Mercedes with the same problem most likely caused by the sensitivity of the electric/hydraulic steering. He rebalanced all four wheels to within 1gm. He said usually the machines note "ok" for 5gms or under. After having all four within 1gm.....what can I say...vibration gone!
He also used an adaptor which sits inside all 5 lugs, instead of using the center hole only while balancing. He said that this is the best way to simulate the tire being on the car.
I was intially thinking along the driveline, but maybe our steering is really sensitive to really precise balancing.
It's worth a shot to pay a tire tech an extra $20 to have him take out the amount of imbalance after the machine states "ok".