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DTS Shudder

6K views 24 replies 7 participants last post by  billdaman 
#1 · (Edited)
Getting ready to put the Caddy back into the dealer to fix a shudder.

Does anyone else have or has had this problem:

2006 47,000 Miles

Shudder felt at and below firewall with vehicle moving :

1. Full Throttle between 2500 and 4000 RPM - Straight line
2. Half throttle 2500 - 4000 RPM - left turns 15- 60 degree turn
3. Half throttle 2500 - 3500 RPM - left turn 80+ Degrees

I cant find any TSB that fully describes this problem, but there are many other DTS owners that describe having the same issue without a solution. The internet and the forum is full of owners that complain of shudders and they are not out of balance tires I am refering to.

So far replaced
1. Tires three new sets, multiple balancings
2. Strut mounts
3. Control arms and ball joints
4. Upper and lower front engine mounts
5. Right axle


Other Possibilities I am considering:
1. roller surfaces inside the inner cv joint housing,
2. Rear engine mount
3. Improperly tightened (torqued) axle (Wheel)
4 Run out on the hubs or due to corrosion on the hubs causing the rotors to not sit flush
5. Harmonic balancer on the engine
6. Back pressure or loose material in the Catalytic converter
7. Failure in Traction control system
8. Torque converter

Has anyone else FIXED this problem, if so how? If the dealer cannot figure it out next visit, I will take the next step and contact GM, ask that they will send out a rep to drive the car, verify, and figure out the problem.

BTW At this point finding a different dealer will not be the solution, as I am currently working with the second dealer. One Thing I have not done to date is to take a ride with the service advisor, but I am holding that for last as the problem does not always present itself and the advisor ride is usually the final step before calling in Sales service and marketing zone reps.
 
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#2 ·
Billdaman


Check the trim height

Front stabilizer links maybe wronge ones, will change trim height

Front engine mount to engine mount bracket, bolts missing and bracket twisted
Out of shape

Wronged engine mount. Some one may have put in a 2001 to 2005 mount
The just cut off the alignment pin to make it fit.

Does car have a lot of torque steer?

Has anyone installed EVA to find if it’s coming from the frame or if it’s rotational?
Can use the strobe off the EVA to check the right axle (I put in 3 before I got one that was good)

The EVA can also tell if a vibe is coming from ALT.P/s Pump, A/C comp, Harmonic balancer, and Torque converter.

Make sure right axle is level. Frame could be bent at mounts. Had to shim mount to improve
Problem.

Hope this is of some help.
 
#6 ·
billdaman,
I'm not sure if you've already been in touch with Katie about this, but we're available to you to check into this further. We can be reached via email at the address indicated below or through the forums messaging system (include your name, contact information, a summary of the situation, and the last 8 digits of your VIN).

Sarah (Assisting Katie), Cadillac Customer Service
 
#8 ·
J 38792-AElectronic Vibration Analyzer


The J 38792-A ,electronic vibration analyzer (EVA), is a 12–volt powered hand-held device,similar to a scan tool, which receives input from an attached vibration sensoror accelerometer and displays the most dominate input frequency(ies) (up tothree) on its liquid crystal display. The vibration concern frequency(ies) areobtained through the use of the J 38792-A whilefollowing the Vibration Analysis Diagnostic Tables. The frequency(ies)obtained, when applied to the Vibration Analysis Diagnostic Tables, are used asa primary input to help determine the source of the vibration concern.

EVAVibration Sensor




The J 38792-A vibrationsensor incorporates a 6.1m (20ft) cord, that allows thesensor to be placed on virtually any component of the vehicle where a vibrationconcern is felt.
The J 38792-Acontains 2 sensor input ports which can be activated individually to allow for2 individual vibration sensor inputs. The vibration sensors can then be placedin 2 different locations in the vehicle and their individual inputs can be readwithout having to stop a test, move the sensor and resume the test. The use of2 vibration sensors can help in more quickly finding and recording an accuratefrequency of the vibration concern, and in more quickly making comparisonsbetween 2 different areas of a single component, or a vehicle system, duringthe diagnostic process.
EVA Vibration Sensor Placement

Properplacement of the J38792-A vibration sensor (accelerometer) is critical to ensure that propervibration readings are obtained by the J 38792-A . Thevibration sensor should be placed on the specific vehicle component identifiedas being the most respondent to the vibration. If no component has beenidentified, install the sensor to the steering column as a starting point.
EVA Vibration Sensor-to-ComponentAttachment

Important: The J 38792-Avibration sensor must be attached to vehicle components in the manner indicatedin order to achieve accurate frequency readings of the vibration disturbance.
The vibration sensor ofthe J 38792-Ais designed to pickup disturbances which primarily occur in the vertical plane,since most vibrations are felt in that same up-and-down direction. The J 38792-Avibration sensor is therefore directional sensitive and must be attached tovehicle components such that the side of the sensor marked UP is always facingupright and the sensor body is as close to horizontal as possible. The sensormust be installed in the exact same position each time tests are repeated orcomparisons are made to other vehicles.
The J 38792-A vibrationsensor can be attached to vehicle components in various ways. For non-ferroussurfaces, such as the shroud of a steering column, the sensor can be attachedusing putty, or hook and loop fasteners. For ferrous surfaces, the sensor canbe attached using a magnet supplied with the sensor.

EVASoftware Cartridge




The J 38792-A uses asoftware cartridge, the J38792–60,which provides various information to theJ 38792-A . The J38792–60 provides theJ 38792-A with anadditional feature which can be selected and utilized to assist in diagnosingvibration concerns.
Important: The Auto-Mode function of the J 38792-A cartridge,J38792–60, is designed to be used in SUPPORT of the VibrationAnalysis Diagnostic Tables ONLY.
This support-feature isavailable through the J 38792-AAuto-Mode function. When selected, the J 38792-A willprompt the user to select which one of 2 vehicle systems (vehicle speed orengine speed), is the SUSPECTED source of the vibration concern. Using theinputted vehicle data parameters along with the most dominate vibrationfrequency obtained, it will identify a SUSPECTED source of the vibrationconcern, such as first-order tire and wheel. This can be a useful feature whenused in conjunction with the Vibration Analysis Diagnostic Tables, to confirmresults obtained through the diagnostic process.

EVASmart Strobe Function




The J 38792-A can beused to identify some rotating components/systems which exhibit imbalance IFthe component rotational speed is the dominant frequency of the vibrationconcern. The J38792-A is equipped with a strobe light trigger wire which can be used withan inductive pickup timing light, J 38792-25 , orequivalent included with the J38792–KIT, oravailable separately. Using the Smart Strobe function enables the user to inputthe vibration frequency to which the strobe will flash. By marking thesuspected rotating component, such as a pulley, adjusting the strobe frequencyto match the dominant vibration frequency at the engine RPM noted duringdiagnosis, and then operating the engine at that specific RPM, the mark on theobject will appear to be stationary if that object is imbalanced.

EVAStrobe Balancing Function




The J 38792-A can beused to identify the light spot on a propeller shaft IF the propeller shaftrotational speed is the dominant frequency of the vibration concern. The J 38792-A isequipped with a strobe light trigger wire which can be used with an inductivepickup timing light, J 38792-25 , orequivalent included with the J38792–KIT, or available separately, and in conjunction with theJ 38792-Avibration sensor to identify the light spot on a propeller shaft and to help inmaking a determination as to when propeller shaft balance is obtained.

Averaging/Non-AveragingModes




The EVA provides 2 modesof displaying the most dominate frequencies which the EVA vibration sensor(accelerometer) detects; averaging and non-averaging (instantaneous).
The averaging mode usesmultiple vibration samples taken over a period of time and then displays themost dominant frequencies which have been averaged-out. Using the averagingmode minimizes the distractions caused by a sudden vibration frequency beingdisplayed that is not related to the concern vibration, such as from pot holesor from uneven road surfaces.
The non-averaging(instantaneous) mode is more sensitive to vibration disturbances than theaveraging mode. Using the non-averaging mode will generate instantaneousfrequency displays which are not averaged across multiple samples over a periodof time; the specific vibration frequencies that occur at a specific momentduring diagnostic testing will be displayed at that moment. The non-averaging(instantaneous) mode is useful when measuring a vibration disturbance thatexists for only a short period of time or during acceleration/decelerationtesting.
When operating the EVA inthe averaging mode along with the Auto Mode, “A” will be displayed along thetop of the screen to the left of the vibration sensor input port being used.When operating the EVA in the averaging mode and the Manual Mode, “AVG” will bedisplayed along the top center of the screen.
When operating the EVA inthe non-averaging (instantaneous) mode along with the Auto Mode, “I” will bedisplayed along the top of the screen to the left of the vibration sensor inputport being used. When operating the EVA in the non-averaging (instantaneous)mode and the Manual Mode, the top center of the screen will be blank.

EVADisplay




The most dominant inputfrequencies, up to three, received from the J 38792-Avibration sensor, are displayed in descending order of amplitude strength.
The frequency readingsare displayed along the left side of the screen, followed to the right byeither a bar graph or the suspected source of the vibration – depending uponthe mode selected, then the amplitude reading for each frequency along theright side of the screen. The top row of the screen indicates the units ofmeasure being displayed for the frequencies along the left side and for theamplitudes along the right side. The top row also indicates the vibrationsensor input port which was selected on the keypad (A or B) and which mode wasselected: averaging or non-averaging (instantaneous).
The frequency(ies) can bedisplayed in either revolutions per minute (RPM) or revolutions per second;Hertz (Hz). The selected display type (RPM or Hz) will be indicated at the leftside of the screen, above the frequency readings.
When the AUTO MODEfunction is not in use, a bar graph is displayed next to each frequency toprovide a quick visual indication of the relative amplitude strength.
When the AUTO MODEfunction is being used, the suspected source of the vibration is displayed nextto each frequency to provide support to the diagnostic process.
The actual amplitudestrength of each frequency is displayed at the right side of the screen andshown in G's-of-acceleration force.
 
#9 ·
Vibrate Software Description and Operation


TheJ 38792-VS ,Vibrate Software, is a computer software program which is designed to be usedin support of the Vibration Analysis diagnostic tables, along with theJ 38792-A ,Electronic Vibration Analyzer (EVA) and a scan tool, to help in determining thesource of a vibration concern. The J 38792-VS isdesigned to provide quick calculations and produce a chart of the rotationalspeeds and frequency ranges for specific vehicle systems and components, basedupon vehicle data parameters inputted by the user.
The J 38792-VS usesthe vehicle data parameters, such as axle ratio, number of engine cylinders,etc. to create the base chart, depicting the relationships of the variousvehicle systems and/or components. The chart view can be modified to show datarelated to vehicle speed only, engine speed only, or both vehicle speed andengine speed. The user can then plot the dominant frequency reading obtained onthe J 38792-Awhich correlates with the vibration concern, and the engine RPM obtained on ascan tool which correlates with the concern. Once these pieces of data arecorrectly plotted, the chart will point to the source of the vibration concern,which should confirm the results obtained through the following the VibrationAnalysis diagnostic tables.
 
#10 · (Edited)
Danog, this is beautiful! So now when the response from the service writer is "Could not duplicate" or "No problem found" or "Operating within GM specifications" we can call for the installation of the EVA and validadte the issue without a loy of debate. Thank you!

BTW we cannot see the links as it appears that they are for SPO access only. here is a link that I found that gives an overview of this equipment. Great stuff! http://www.vibratesoftware.com/html_help/2011/Diagnosis/EVA/EVA_Selection.htm Do you have some screen shots of what the sensors look like? Does this equipment use the modal from the chassis as a baseline and compare it with the frequencies from the other two vertical inputs?

Finally for GM dealer failure analysis does this machine require SPO expertise and gets shipped to the dealer on a case by case basis or should any GM dealer have this equipment and will be able to set it up on any given visit? Thanks again.

Here is the info from the site:

Most automobile vibrations are caused by rotating components that are out-of-balance or out-of-round. Since the engine must be running for these components to begin rotating, the engine's crankshaft will be the point of reference for vibration diagnosis. Every rotating component will have a rotational velocity that is faster, slower, or the same as the engine's crankshaft. Determining the rotational velocity of each component in relation to the engine's crankshaft is the key to an accurate vibration diagnosis.

VIBRATE 5.0 calculates the rotational velocity of each component and graphically represents these velocities on a computer's screen and on a printed Vibration Worksheet. The printed vibration worksheet is for an automobile technician to use while test-driving a vibrating automobile. When the automobile's vibration is present, the technician records the vibration frequency and the engine RPM on the Vibration Worksheet. (The technician will need tools to measure vibration frequency and engine RPM.)

There is a point on the vibration worksheet where the vibration frequency reading and the engine RPM reading intersect. This point should be on, or very close to, a plotted line on the vibration worksheet. The plotted line indicates the specific component group causing the vibration. The technician can diagnose which component in the component group is causing the vibration by using the procedures outlined the Vibrate 5.1 Help file or in the vehicle manufacturer's service manual.

Automobile and truck technicians like this method of vibration diagnosis because the vibration worksheet is easy to understand and the technician is not required to perform any mathematical calculations.

----------

This is the ticket...It just so happens...imagine the coinicidence here... that the site that rents this EVA equipment to the public uses the CADILLAC DTS IN ITS ADVERTISEMENT! yep....must be a popular vehicle to use this equipment on and it appears that DTS owners are a big part of their customer base. More to come as I deep dive this equipment before what is hopefully my last No trouble found visit to the dealer.Here is a sample modal diagram for a Cadilac DTS:

2001 Cadillac DTS vibration worksheet downloaded free from vibratesoftware.com ©


Kent Moore EVA displaying a 16 hz, .03g vibration at 70 mph and 2000 rpm. Using the above vibration worksheet, this would indicate a T1 vibration (yellow area) which would be a tire speed related vibration issue. ©
 
#11 ·
According to the dealers "thorough" analysis my "Shudder" that I only get when accelerating and turning left is "Torque Steer"

TORQUE STEER??? What does torque steer have to do with a shuddering vibration???? OMG.. Nothing else to do but seek an independent drive line shop now. Can I get reimbursed from GMPP for work done at independent shops? Maybe the GM Customer service person can answer this question for me and please--- not off line but directly on the forum!
 
#18 ·
Hello billdaman,
We would not be able to reimburse you for work performed at independent shops (barring extenuating circumstances like an emergency repair out of state or the like). If we can follow up on your service visit, please let us know! We would need contact information, the last 8 of your VIN, and the name of your dealership to get started, which is why we tend to move those conversations to private messaging.
Sarah, Cadillac Customer Service
 
#12 ·
Have them take you for a ride in a different DTS and see if it has the same condition.

All front wheel drive cars have Torque Steer. If any it should have more to the right not To the left. The right is closest to the rear end and would have more torque. The rear end is on the right side. The shaft goes through the center of the trans and out to the left.

Has the rack been replace and the front end align to spec. What about the end links are they the same size on both ends. Has the front sub frame been centered (lousing all 6 bolts and move the frame so all the bolts fit in the center)??

Has anyone check the right axle is it twisted or bent. Put it up on jack stands have some one in the car and spin the wheels up to 60 and take a screw driver and hold it near the shaft and move it slowly till it just touches the shaft if its straight it will have a mark all the way around.

Is the left output shaft seal leaking? If so the problem is the 3 gr clutch drum bushing Causing the Shudder.

Have you ask to have the Zone engineer drive the car with you?? Do you know who the DSM is. I can look it up for you.
 
#13 · (Edited)
Have them take you for a ride in a different DTS and see if it has the same condition.
The mechanic at the dealer verified the problem with my vehicle, adjusted the position of the upper dog bone strap and drove it again. He then drove another DTS and said it has the same issue and called it "Torque steer" . (The vehicle does not pull or hop...it shudders). When I asked the Service writer if I could take the same vehicle home for a day to verify he said no, but I could drive it.

All front wheel drive cars have Torque Steer. If any it should have more to the right not To the left. The right is closest to the rear end and would have more torque. The rear end is on the right side. The shaft goes through the center of the trans and out to the left.
It most definitely shudders on left turns and it does so at several different levels of steering angle and engine RPM

Has the rack been replace and the front end align to spec.
They replaced the "Steering gear" in 2011 - P/N 19208459 I assumed that was the Rack and Pinion assembly. The front end has since been aligned at two different Cadillac dealers

What about the end links are they the same size on both ends. Has the front sub frame been centered (lousing all 6 bolts and move the frame so all the bolts fit in the center)??
What dimensional difference should I be measuring between the two end links? The engine has been out three different times for oil leaks, with the engine being replaced the last time so centering of the cradle is something to check.

Has anyone check the right axle is it twisted or bent. Put it up on jack stands have some one in the car and spin the wheels up to 60 and take a screw driver and hold it near the shaft and move it slowly till it just touches the shaft if its straight it will have a mark all the way around.
Again I will ask them to check. The right Axle has been replaced in 2011. They have indicated that they have "Checked everything" but never give me anything in writing

Is the left output shaft seal leaking? If so the problem is the 3 gr clutch drum bushing Causing the Shudder.
The right axle seal was replaced several months ago for "leakage" I have not observed leakage on the left yet

Have you ask to have the Zone engineer drive the car with you?? Do you know who the DSM is. I can look it up for you.
I have been told by the dealer that I not them have to contact GMPP. They claim that the handling procedures are different. Danog, I would appreciate the contact information for the Zone rep if possible. I reside in Cleveland Ohio.

Very frustrating dealing with the dealer, being treated like a second class customer.
 
#16 ·
Diagram Line Parallel Table Furniture

When they replace the engine did they check the wheel alignment its part of the job.
Any time you remove or center the front sub frame you have to do an alignment.
We drop the engine, Trans, struts, and rack down through the bottom as a unit

Does it have a lot of torque steer, (pulls hard to the left)? Do you know how to check the bias axle angles?
 
#17 ·
View attachment 101203
When they replace the engine did they check the wheel alignment its part of the job.
Any time you remove or center the front sub frame you have to do an alignment.
We drop the engine, Trans, struts, and rack down through the bottom as a unit

Does it have a lot of torque steer, (pulls hard to the left)? Do you know how to check the bias axle angles?
Recently had both control arms and ball joints replaced (sealed Ball joints were leaking at 44K..wonder why when the engine came out 3 times) When they replaced the control arms they aligned the front end. The Car does pull slightly left under VERY hard acceleration, but it shudders when launching and turning left. So if I am going say 20 MPH and then apply WOT plus turn the wheel left just enough to cross into the opposite lane it shudders (passenger and driver can feel it cross car) left to right until you stop accelerating.

I will try to determine the slope of the differential pan to the ground cross car. Thanks! BTW do you have the Zone manager info for Cleveland Ohio? Please PM me if you can. Thanks!
 
#25 ·
Yes now that it is fixed there were other symptoms that were related to the sticking CV Joint:

1. Launch Shudder (Left turns)
2. Shudder at highway speeds when downshifting from 3rd to 2nd and steering wheel turned left as in shifting lanes Left to right
3. Harsh down WOT shifts / shudder on WOT downshifts 3rd to 2nd and 2nd to 1st
4. Various highway drivability issues barely detectable vibrations

All I can say is that the car runs better than ever, and it took several dealer visits to finally get fixed
 
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