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Down Shift Whine On '07 Trailblazer

hoobygt

By hoobygt
in Ask A GM Technician

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hoobygt Enthusiast

hoobygt

Posted
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I have a down shift whine coming from the transmission on my '07 Trail Blazer. It is a GM Certified vehicle and both times I've taken the truck in to have it looked at (at the GM dealership where I purchased it), they say that the sound isn't coming from the transmission, but rather my rear wheels (they are worn slightly irregular, but due to improper inflation from the previous owner they had said when I purchased the vehicle). I'm not a technician, however, I know it is false that it is coming from the rear tires.

 

While slowing down, easier to hear while slowing down from 40+ mph, the transmission will begin to whine around 30 mph. It starts out with a high pitched whine and slows down until the truck down shifts (i'd assume) and then the whine picks back up and slows down until it down shifts yet again to first gear. It is coming from the engine/transmission area, because with the radio and heater/ac off I can hear it from the front of the vehicle. You can also hear it with the window down.

 

I don't have a sound clip, but the big letters may show the "decrease in sound." All caps means louder, mixed caps and small means lower volume, and small letters means lower sound.

 

WEEEEEEEEEEEEeEeEeEeEeEeEeeeeeeeeeeee

*down shift*

WEEEEEEEEEEEEeEeEeEeEeEeEeeeeeeeeeeee

*down shift*

WEEEEEEEEEEEEeEeEeEeEeEeEeeeeeeeeeeee

*vehicle comes to a stop*

 

The whine is not audible or doesn't occur when accelerating. It hasn't affected the drive-ability of the vehicle either.

 

I had an '05 Colorado Z71 Crew with the 4-speed. My dad had an '03 and currently has an '04 full-size Sierra with the same transmission. My grandpa also had an '06 Sierra. He now owns an '08 (but with the 4-speed) and I've NEVER heard this noise from any of those trucks or transmissions.

 

Is it not a transmission noise, and maybe a characteristic of the I-6?? The Colorado had the I-5, but never heard such a noise from the truck at all, either.

 

Please help!

 

Greg

hoobygt Enthusiast

hoobygt

Posted
  • Author
Posted

they already replaced the "flaking" bearings in the rear end that last time I was in. The sound is not coming from the rear, so I do doubt that it is the rear differential. Or are you saying it is the front diff? It clearly is coming from the front. When in the cabin, it sounds as if it is coming from underneath the shifter/console.

 

Would/could it have any connection to the TCC or whatever it is called?

 

Greg

hoobygt Enthusiast

hoobygt

Posted
  • Author
Posted
was the rear pinion seal replaced before the noise started?

 

The noise was present before I took the truck in and still is there after they replaced all fo the bearings and seals on the rear differential. Everytime they've had the vehicle they keep saying the noise is coming from the tires when I slow down. Tires don't whine and pick up speed/noise when you are slowing down. And it isn't just a coincidence that the noise happens three times, each time the transmission would seem to down shift.

 

I appreciate the help and keep it coming! I know it is nearly impossible to diagnose it over the computer :cheers:

 

Greg

savage99ss Enthusiast

savage99ss

Posted
Posted
was the rear pinion seal replaced before the noise started?

 

The noise was present before I took the truck in and still is there after they replaced all fo the bearings and seals on the rear differential. Everytime they've had the vehicle they keep saying the noise is coming from the tires when I slow down. Tires don't whine and pick up speed/noise when you are slowing down. And it isn't just a coincidence that the noise happens three times, each time the transmission would seem to down shift.

 

I appreciate the help and keep it coming! I know it is nearly impossible to diagnose it over the computer :cheers:

 

Greg

 

 

I had a whine which i thought was in the trans. This was when my Camaro was under warranty. Well it turned out to be the rear. I had to take three times to get it right.

  • 2 weeks later...
hoobygt Enthusiast

hoobygt

Posted
  • Author
Posted

I've tried to get in contact with the dealer, but the service manager that I dealt with will not return my calls, even after I leave a message. I have had several contacts with GM customer service (albeit that most of them have been email, which isn't always the best), and have not had results. I'm going to continue to drive it until it gets progressively worse or something just plain gives out, I guess. The dealer keeps saying there is nothing wrong, when I'm sure there is. I've had the chance to ride and drive a few other trailblazers, and the sound is not present on the ones I drove.

 

I have a GM Certified warranty for about another 6-7K, powertrain 5-year/100,000 mile for another 2 years, and also purchased the Major Guard Protection Plan (waste of money usually, but I'm happy I purchased it for this vehicle; first "extended" warranty I've ever purchased). So if something happens, I should be covered through one of those warranties.

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