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Hi, I have a 2002 trailblazer LTZ and it is making a small vibration/ slight grinding metal on metal noise. The sound only happens while it’s driving 35 to 40 MPH or higher. It stays the same sound reguardless of rpm Just a slight low growl driving. It is not the wheel bearings, has anyone had the same issues and could possibly tell me what the issue could be? It seems to be near the back end of the motor or near transmission but I’m not sure. It is a 4x4 and the transmission has been changed out for a newer one. I just bought the vehicle so I’m not sure if it was happening before. Any ideas where to start first?
 

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Immediately.... it comes to mind, according to your info..... you might have a cracked flexplate. The "constant speed" part and you saying it's between the engine and the transmission.... would need a somewhat constant RPM too.... but this is complicated because I'm here and you are there with the vehicle.

Okay.. that said..... the transmission mount, if it's collapsed, missing or not firmly bolted in.... maybe the noise is created there and transmitting the sound into the frame...... this is tough, like I said......not being there.

At this point.... it's a lot of guessing.

I'm going with the noise is the result of the transmission replacement.... units can be destroyed by a bad installer.
  1. Something loose... maybe crank-to-flexplate bolts looser not torqued correctly
  2. Something broken/missing ... engine-to-bellhousing alignment pins are gone...
  3. Flexplate cracked, cracking
  4. Flexplate-to-torque converter bolts loose/missing
  5. Cracked bellhousing because someone tried to draw the transmission to the block with bolts.... bad idea!
  6. Out of balance driveshaft, joint missed and not sitting in correct place
  7. Stuck in 4WD
  8. No fluid in transfer case
That's as far as I want to go at this point.... all that is worst case spitballing......
 

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Discussion Starter #3
Don’t know, I’m thinking that it is the torque converter it is not making the noise a cracked flex plate would because it will idle fine. The sound happens when I hit 40 and up and I’m thinking it’s also when the car warms up. Transmission was switched for a 2 wheel drive instead of a 4 wheel drive. Also the actuator is clicking so I don’t know if it has any correlation.
 

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Check the ball joints mine did similar when they were installed broken by not me...
 
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