2004 Chevy Suburban drive train noise?

Tiny
TEIDES
  • MEMBER
  • 2004 CHEVROLET SUBURBAN
  • V8
  • 4WD
  • AUTOMATIC
  • 200,000 MILES
When driving at 60+ coasting downhill sometimes there is a higher pitched noise ( like a motor spinning), the RPM's drop until I hit the gas and the noise stops and rpm's return to normal. This does not occur when I'm drifting downhill in neutral, only in drive. Seems to be in the drivetrain.
Monday, October 18th, 2010 AT 1:27 PM

7 Replies

Tiny
MIKE H R
  • MECHANIC
  • 3,094 POSTS
Check the fluid in the front and back diferental, fluid could be low. What it sounds like is that when it has back pressure from coasting it is putting pressure on the gears.
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Tuesday, October 19th, 2010 AT 9:15 AM
Tiny
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  • 4 POSTS
The fluids in all drive cases have been ghanged. That's not the cause of the noise.
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Tuesday, October 19th, 2010 AT 11:19 AM
Tiny
MIKE H R
  • MECHANIC
  • 3,094 POSTS
When you are coasting down hill with it in gear and you foot off the accelerator can you feel the engine holding the car back or does it feel like is free wheeling. Can you find out the general area of the noise? Is it in towards the front or the rear?
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Sunday, October 24th, 2010 AT 10:14 AM
Tiny
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  • 4 POSTS
When coasting downhill the engine initially is holding back then seems to let go, the RPM's drop and you can hear a freewheeling sound coming from the front as best I can tell. I'm starting to think the torque converter is disengaging.
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Sunday, October 24th, 2010 AT 9:24 PM
Tiny
MIKE H R
  • MECHANIC
  • 3,094 POSTS
Ok, we have eliminated the rear, Did you change the transmission fluid and filter. The only thing I can think of that lets it free wheel like that is the transmission or the torque converter. With 200000 miles on it I wold have the transmission checked first. That way if there is a problem with circulation it would be easier to fix than pulling everything apart to get at the converterjust to find out the problem is in the valve body of the transmission.
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Tuesday, October 26th, 2010 AT 10:00 AM
Tiny
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Mike, yes I changed the transmission fluid and filter about 10,000 mi. Ago. What is the valve body on the transmission? Is it external?
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Tuesday, October 26th, 2010 AT 2:21 PM
Tiny
MIKE H R
  • MECHANIC
  • 3,094 POSTS
It is inside the transmission, I think it is in the rear end. The gears are not meshing right and making the sound. I have seen it before where the rear waould make a wi9ning sound. Try to pinpoint about where the sound is comming from. Is it in the front or towards the rear?
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Tuesday, November 2nd, 2010 AT 8:54 AM

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