Jump to content

Recommended Posts

Posted

You do know that GM once had an official memo for the roof repair but have since pulled it - no official reason but suspect due to the bows coming undone again - so it's definitely the roof, and I do not think we'll see a future fix from GM

 

Reduce inputs into the vehicle and/or the "rip" roof fix are the only ways to go

 

I'm still not convinced that the roof is in play. My dealership pulled my headliner down to inspect the bows and they were intact, while I had the buffeting. Maybe they pulled the TSB because they found it to be irrelevant?

 

If it was body mount related, what's involved in changing them?

 

 

Sent from my SM-G935F using Tapatalk

Posted
The issue from a high level stems from weight saving efforts which resulted in paper thin sheet metal. To keep the sheet metal from vibrating (booming) and flexing (buffeting) it absolutely HAS to be attached firmly to its braces. In our case, the roof, due the roof panel being compressed from the edges, wants to pop off of the roof bows rather than be stretched tight against the roof bows (how they should be). As a result, the roof pops off and you are driving in a giant drum. This is a manufacturing defect.

 

... I made some plastic pieces to wedge between the roof rack rails and roof. You could make some out of a 2X4's if you wanted to test this (yeah, that would look rather 'neck on one of our trucks) When they are in place, zero booming and buffeting. Remove them, both come back. Keep in mind my dealer put Dynamat on my roof and lots of extra glue to hod the roof to the bows. When the bows again became detached, the issues returned. Put the roof back onto the bows, the issues go away. I know of no other better way to confirm root cause than to be able to make a chance and get an issue to come/go at will.

 

Find a way to pin your roof down and you to can get the truck you thought you were buying.

 

Sheetmetal density is different from gens 2, 3, and 4, but no difference from one gen 4 truck to another that doesn’t exhibit issues on this thread. Kind of agree with your assessment and evaluation with the detached bow piece. With the difference in suspension/length/engine size/ and tires, there could be multiple fixes, one solution may not fit all. You are not the first one to rig up something on their truck to get some satisfactory relief.

 

Good post though, keep refining the plastic wedges then paint them body color, only you and the dealer will ever know :). Disagree with rigging your truck then thinking this is what you paid for.

Posted

It's still speculation re: improved body mounts, but here's picture and link if anyone wants to compare to a 16 .. best way is to go test drive some 17s

 

http://www.tahoeyukonforum.com/threads/2017-yukon-xl-denali.85107/page-4

Hard to tell. Would need to know which mount this person took the person of, as there are 3 or 4 different part numbers front-to-back in the SUV.

 

One way we can confirm whether or to GM changed the body mounts is by the part numbers. Once the parts catalogs are out for the 2017's, we can chance vs the 2015-16. And in case GM, is playing any funny business and went back to the 15/16's and updated the parts numbers without the usual showing the old part number superseded with the new one, I made a compare list of the parts numbers for my 2015 about a year ago. Now, a part number change isn't proof the body mount was changed to address the buffeting. But it would be suspicious!

 

Could the body mounts be a factor? Absolutely. I found numerous technical papers over a year ago published in SAE and other industry related organizations that were specifically about body droning and pulsing noises and several about the role body mounts plays in the final result. Essentially, the body mount is barter the frame-to-body stiffness system, and hence the resulting natural frequency. A bad selection can make a big difference.

 

And to add to the the story, the new platform (2015- SUV and 2014- pickups) use an all new "shear type" body mount to reduce horizontal motion/jiggle. From the info. Could find, they do this by restraining the horizontal movement via some kind of sleeve inside, or something like that. Essentially, with a slight bit of horizontal movement, the body mount "bottoms out". Could,this affect the transmissibility of any and all vibrations from the power train and/or rolling gear (tires, wheels)....absolutely.

 

Still need something to respond to all that vibration. Something like a big drum skin. Wonder what it could be......

Posted

I'm still not convinced that the roof is in play. My dealership pulled my headliner down to inspect the bows and they were intact, while I had the buffeting. Maybe they pulled the TSB because they found it to be irrelevant?

If it was body mount related, what's involved in changing them?

Sent from my SM-G935F using Tapatalk

Marc, did you have a look at the cross bows when then had it apart? They are the flimsiest things possible. Even if attached, it no wonder the thing still booms like a drum skin. I suspect that is what GM concluded - that even if they keep the roof skin attached, the cross bows do not offer sufficient stiffness to resolve the issue. So, no point in trying. And of course, it's not likely GM will ever change the design of the cross bows or add more ..... totlly impractical in a completed vehicle. Best plan is to deal with the complaints and change the design for next time.

Posted

We can go round and round on body mounts, shocks, etc... but at the end of the day, the truck must tolerate the real world. I suggest for all having issues that they pin down the roof and report back.

Posted

Any thoughts on why some of the vehicles exhibit the booming/buffeting and others do not? We have a 2016 Cadillac Escalade with no issues whatsoever.

 

Contrary to that, we also have a 2016 Z71 Tahoe (my daily driver) which has both the booming and buffeting and has now been in the shop for a month..

Posted (edited)

So yesterday morning. Drove 8 miles, ~38 degrees outside, had thumping in rear from cold shocks that resonated some in cab. Later in the day... Drove it the rest of the day about 45 more miles, no thumping. NO ISSUES at all. Temps 50-60 degrees.

 

Cold oil in shocks adds to the sound issue.

 

If mine stays the way it currently is, I like the truck a lot. Crossing my fingers that with time and mileage it holds up like it should.

 

I keep my cars for a long time and have expectations of minimal issues as it ages.

 

I have a 20 year old Dodge Ram 1500 4x4 pickup that is still running strong. It is the rust that will send it to the junkyard.

Edited by zfasts03
Posted

Any thoughts on why some of the vehicles exhibit the booming/buffeting and others do not? We have a 2016 Cadillac Escalade with no issues whatsoever.

 

Contrary to that, we also have a 2016 Z71 Tahoe (my daily driver) which has both the booming and buffeting and has now been in the shop for a month..

 

The most common thoughts on this thread are the roof, suspension, AFM, ANC, thin sheet metal, rear axle, tires, wheels, and body mounts. If a truck does not exhibit any of these issues, some folks even say it's the people not the trucks. GM may correct some of the issues on generation 5, but for this one they are just throwing stuff on the wall to see what sticks.

 

As for your trucks, the glaring differences (suspension and AFM) will be up to the dealer to get lucky, 'cause you won't be able to do anything about them and maintain some type of warranty. Your Escalade is not out of the woods, there is about a half dozen owners on the thread that had some of the worse problems. So don't change anything on your Cadillac, you might screw something up.

Posted

I'm still not convinced that the roof is in play. My dealership pulled my headliner down to inspect the bows and they were intact, while I had the buffeting. Maybe they pulled the TSB because they found it to be irrelevant?

 

If it was body mount related, what's involved in changing them?

 

 

Sent from my SM-G935F using Tapatalk

 

"Intact" can mean a lot of things. The roof can be touching them at rest and lift and buffet at speed. Find a way to strap something to the roof and hold it down. If the issue is unchanged than maybe you have other issues. Otherwise, the roof is the large expanse of sheetmetal that can change the interior air volume and cause the buffeting.

 

Frank

Posted

It's still speculation re: improved body mounts, but here's picture and link if anyone wants to compare to a 16 .. best way is to go test drive some 17s

 

http://www.tahoeyukonforum.com/threads/2017-yukon-xl-denali.85107/page-4

 

Per Nissan's tech paga...

 

Nissan's Titan and Armada are using "hydraulic body mounts" to reduce vibration.

 

Maybe all of these body on frame vehicles exhibit vibrations, but it comes down to the materials and parts the manufacturer used to eliminate them.

 

And GM choose the cheapest part available.

Posted

 

"Intact" can mean a lot of things. The roof can be touching them at rest and lift and buffet at speed. Find a way to strap something to the roof and hold it down. If the issue is unchanged than maybe you have other issues. Otherwise, the roof is the large expanse of sheetmetal that can change the interior air volume and cause the buffeting.

 

Frank

Could you speculate on how tire balancing can influence/eliminate buffeting if the roof was a factor? Are you suggesting that my out of round tires (since fixed on 2 different sets) caused my roof to shake?
Posted (edited)

As Elripster mentioned he can make this stop by wedging pieces under the roof rack cross rails to prevent roof movement. Maybe adding a molding to the outside will reduce flex and eliminate the speaker/subwoofer effect.

 

So, how would it be to attach to the outside of the roof either longitudinally (preferred for cosmetics and air flow) or maybe transversely a body side molding (w/symetrical profile).The 3M two way tape and the polyurethane molding is energy absorbing and the molding would add rigidity to the panel. It can also allow for protection of the roof panel from damage when carrying cargo on the roof. The molding could easily be body color and be a standard feature on new models and a add on by the dealer as per a TSB for those who complain about the booming/buffeting from the roof.

 

I estimate the moldings would be 1" wide and be place longitudinally directly between the raised stamped areas of the roof. The moldings would need to be thick enough to sit about 3/16" proud of the stamped ridges. It would run a similar length as the roof side rails, maybe a little longer.

 

If a longitudinal placement does not resolve the cabin noise then a transversely mounted configuration may need to be explored.

 

I remember working as a Dodge Tech about 25 years ago and seeing the installing of moldings down the roof as part of a roof rack install on a Dodge Caravan.

Edited by zfasts03

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Latest Articles

  • Posts

    • As a matter of amusement I’ll leave this conversation with this. Do you beat the government average fuel estimate? Statistics are a guide to me. Not a rule. Someone once said I have to have the last word. If true and possible may be. I’ll blame that on working in a family business.
    • That is a fair point, and I agree that trying to log “everything in the truck” would be the wrong direction.   There are a lot of modules and a lot of traffic. If the product became a full-truck datalogger, the amount of data would get huge very quickly, and most owners would never use it.   I think the first useful version would need to be narrow: - powertrain-side event evidence - selected high-value parameters - communication / voltage / reset events - pre/post event window - short report first, raw log only as backup   One distinction I should make is between active OBD/PID polling and passive bus capture. If you are polling PIDs through OBD, then yes: the more parameters you request, the lower the effective sample rate becomes, and you are adding diagnostic traffic to a vehicle that is already busy running itself. With passive CAN capture, the recorder is not asking all the modules for data. It is listening to traffic that is already on the bus. So it does not consume vehicle bus bandwidth in the same way that a scan tool polling hundreds of PIDs would. But your point still applies in a different way.   Even if passive capture does not add bus traffic, the recorder still has limits: - processing rate - storage rate - timestamp accuracy - decoder workload - event filtering - report size - user attention span   So the answer cannot be “log everything and let the user figure it out.” The product would need to store enough raw evidence to be useful, but only decode, graph, and present the important parts around the event.   A practical report should probably show: - what triggered the capture - how much pre/post data was preserved - which selected parameters changed - how those values compared to baseline - whether the same pattern happened before - whether any voltage, reset, bus-off, lost-message, or communication fault occurred - selected graphs around the event - raw data only as supporting evidence   So I agree with you. More data is not automatically better. The real product is the reduction from raw data into a useful event report.
    • That makes sense, and I agree with most of that.   I think the product would need both: 1. a default powertrain template, so it is useful out of the box; 2. user-selected priority parameters, so the owner or shop can choose what they want to see first.   Different users are going to care about different things. One owner may care about oil pressure and voltage. Another may care about misfire trend, AFM/DFM behavior, or U-codes. A shop may want communication events and repeatability first. Your baseline point is probably the most important one. Raw data is not very useful unless the report can show what normal looked like for that vehicle under similar conditions.   The way I would think about it is: - start with a basic known-good baseline - learn normal behavior for that specific vehicle over time - allow the event to be overlaid against baseline - show whether the event was a one-time spike or a repeatable pattern - provide a simple severity level, but with clear limits on what that severity means   For example, early severity could be something like: - Info: event captured, no obvious abnormal pattern - Watch: value moved outside baseline, but not repeated - Warning: repeatable abnormal pattern under similar conditions - Critical: communication loss, voltage drop, bus-off, reset, or severe repeated event   I would not want the first version to say “replace this part.” That would be overclaiming unless there is repair-confirmed data behind it. It would be more honest to say “this pattern deserves inspection.”   On the OBD port question, I think OBD absolutely has a role. OBD is probably the right place for: - DTCs - freeze frame - VIN - calibration information - normal scan-tool parameters - Mode 6 / enhanced diagnostic data if available The reason I am still looking at an ECM-side recorder is that the failure may happen before anyone connects a scan tool. If the owner plugs in a scanner after the event, the pre-event evidence may already be gone unless the ECU happened to save it. So I do not see this as “OBD versus ECM-side.” I see it more like: - ECM-side recorder: always armed, rolling buffer, event evidence - OBD/DLC companion: DTCs, freeze frame, VIN, calibration, normal scan data - phone/cloud: status, notes, upload, report generation, notifications   I agree that phone connection and push notifications would be useful. I just would not want the phone or cloud connection to be required for capture. The recorder should save the event locally even if the phone is not connected. The phone should help with event marking, download, notes, upload, alerts, and report viewing.   For a default GM V8 event report, would this list make sense? - RPM - calculated load / MAP - throttle position - vehicle speed - gear / torque converter state if available - coolant temperature - oil pressure - oil temperature if available - battery voltage - commanded AFM/DFM state if available - actual AFM/DFM state if available - misfire counters / roughness by cylinder if available - fuel trims - relevant U-codes / communication events - bus-off / lost periodic message / module reset / voltage drop events Which of those would you remove, and what would you add?
    • I went to the county a few years back to dispute my property taxes. To do that I hired an appraiser and a lawyer. The County Assessor wished to argue that the homes in my neighborhood the appraiser used were all 'distressed properties" and not representative of the "Market Average".    My response was," Of the 50 homes in our subdivision 43 of them were "distressed properties" under bank foreclosure and as such "Distressed IS the market". Lawyer about choked on his coffee and handed the Assessor the 'receipts'.    I won that case on the evidence provided by the Lawyer and the Appraiser.    We have the same thing going on here. My statements were based on the GOVERNMENTS NATIONAL DATA and yours on local markets in areas of your interest. They are both correct....   Thing is, this divergence was based on NATIONAL and not on LOCAL. I think you even understand that. But like you said, we are both stubborn and hardheaded.    I do not see any advantage to disengagement.  But that said we can step back to compose ourselves. 
    • Trust me I appreciate the comments and concerns. It's what I was looking for to help me evaluate the situation and what I want to do. I have decided to move forward with the BORA hubcentric slip on 3/8" (.375") with the extended lugs nuts. Fedex says they should be here Monday :). Meanwhile, the dealer got the remote start and Patriot spray in bed liner done over the last couple of days. Also, I installed an inline stop/start eliminator today. Starts back up in what whatever mode you shut it off in, so you don't have to hit the button every time you fire up.
  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...