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Denali 3500 Problems

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Thought I'd share our experiences with our new 2015 Sierra Denali 3500 DRW Duramax. Wife and I love the new truck, and can't wait to tow the camper with it. But, the number of issues we've experienced on a new vehicle is really unexpected! I mean, GM, why?!?


Here's what we have so far with 750 miles on the odometer:


1. Soaked rear insulation (under carpet) on the driver's rear side

2. Whistling noise at 65 mph from center of windshield

3. Headlight complaint


The dealer has already looked at the soaked carpet and said I must have left a window open. They also damaged the rear trim when removing the rear seat :) Spoke to the manager and it's going back in tomorrow for another look. Btw, I confirmed a normal manual car wash will cause the leak to happen. It's really sad that I have to be the one to convince them that my truck has a problem, find the root cause, explain potential solutions, and turn it over to the dealer to see what happens. Engineers usually look for these things before releasing a product to the market, don't they? Ugh


Whistling noise...yep, as described in other threads here. Just discovered that issue today.


New headlights from PIT5374A have been ordered by the dealer, but still on backorder.


On the good side, it is a wonderful truck! Definitely a step up in luxury from our old 2003 Suburban 2500! We've already added an ARE cap, GM/Kicker subwoofer, GM molded splash guards, Lock'er Down console safe, and Weathertech floor mats. Have a Bedrug to be installed for the dogs soon. And, waiting on a steering stabilizer to be released from backorder.


I sure hope GM and the dealer can fix these things. Totally crazy for an expensive vehicle like this to have leaks and whistling noise...just don't understand. Hope you guys are luckier than we are, and maybe this info will be useful for you. And, thank you for letting me vent AND for this forum as it's been very therapeutic for me lol.

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  • 2 weeks later...

I bet the third brake light is leaking.

As for the headlights, there is a huge thread on the 1/2 ton section about this. I hope everything works out for you... BtW, keep a bucket of damp rid in the back seat to soak up some of the moisture in the mean time.

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Thanks 20Bowtie14


We got the truck back tonight after it being in the shop for almost two weeks. Here's what they did:


1. Replaced weatherstripping on rear driver's side door for water leak

2. Replaced center roof marker lamp for whistling noise

3. No parts yet for the new headlights...still on back order after 3+ weeks.


The dealer says they also have trim parts on order to replace the ones that were scratched.


I guess I'm happier (?). I'll take the truck to a self car wash this weekend and test to see if the leak is still there.

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