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2006 DTS Lux III, green silk/shale, bench seat!
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15 Posts
Discussion Starter #1
Hi all,
I have a 2006 DTS Lux III, which I believe does NOT have magna ride.

When I bought it, it had a definite shake--felt like out of balance tires to me. I took it to my tire shop and they balanced the tires and replaced the right front wheel bearing. At that point, I would say about 80% or better that the shake went away.

Last month, I replaced the tires (old Michelin MX4 vs new General RT43). Immediately, I noticed the "shake" about doubled or tripled upon the tire swap. I also noticed the steering was much more responsive, leading me to believe that the RT43 must be significantly stiffer than the old MX4.

While I definitely would describe the original pre-balancing feeling as a "shake," I'm not sure I would describe the lingering issue that way. It feels more like driving on maybe a smooth (relatively speaking) cobblestone road. For example, a freshly paved highway feels like it is bumpy. The feeling is more in the whole car rather than in the steering wheel. The steering wheel feels more like it is bouncing up and down (with the whole car) rather than vibrating left to right as it would with an out-of-balance front tire. I can start to notice it around 20mph, and it gets slightly worse up to about 60mph, where it levels off or maybe even gets slightly better towards 70mph.

Maybe related, I get a pedal pulsing when braking occasionally. It seems inconsistent to me with warped rotors because it is usually not there (in other words, most of the time I can brake soft/medium/hard and I get zero pedal pulsing). It seems like it happens more often after a longer highway drive rather than any other type shorter drive--but I could be wrong about that.

What might be some likely culprits? What might be the best approach to narrowing it down?
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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67,161 Posts
The "Seville Shimmy" is discussed endlessly in Deville and Seville. Google it - "cadillac forums seville deville front end shaking" or something close.

A Hunter Road Force balance can help. Correct manually performed lug nut torque - 100 lb/ft - in a star pattern helps. Insure that the wheel hub, brake rotor, and wheel mounting surfaces are surgically clean and that the wheels have no side-to-side runout.

I use the Cooper CS-5 W rated 235/55/17 tires with the above processes and the car is glass smooth to over 130.

Brake rotors are machined from gray cast iron - so they do not "warp". They DO pick up pad deposits that can cause judder upon brake application. Get out to the boondocks and perform several aggressive stops from 60+. Do not hold the brakes at each stop - drive away immediately and, after the stops are complete, drive at least 3 miles to cool the rotors.

Read the white papers concerning brakes in the EBC and Stoptech websites.


 

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2006 DTS Lux III, green silk/shale, bench seat!
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15 Posts
Discussion Starter #3
In reading about the Seville/Deville issues, it seems everyone trying to fix the issue just keeps replacing parts ($$$$) and rarely gets to the bottom of it. I had this same issue with my 2006 SRX (V8 AWD). It was diagnosed by the Cadillac dealer as a bad torque converter--then the Buick dealer I bought from confirmed the diagnosis and changed the torque converter, but it didn't change the issue at all.

Is there anything that the DTS/SRX/Seville/Deville have in common that could be causing it? Similar drivetrains seem to me the most likely commonality. However, I would expect some change in behavior based on the engine speed or load, and that's just not what it feels like to me, not that I'm any kind of authority.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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67,161 Posts
Read the first para. in Post #2 again.

The much-discussed "Seville Shimmy" has nothing to do with the FWD Northstar torque converter. If the vibration is in the front OR rear end it's due to imbalance, worn suspension/sway bar parts/bushings, wheel/tire out-of-round or wheel/tire/hub runout. Unfortunately, the vibration is usually not caused by the same problem in two or three different cars. It's a case-by-case basis.

For the Seville/Deville the correct lug nut torque is 100 lb/ft in 3 steps in a star sequence. Even simply using a shop's air impact wrench can introduce the vibration.

Do you speak "tire flat spots" ? Drive 10 miles before commencing vibration diagnosis.
 
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