Whining/spooling/spinning sound on deceleration

[SwampSurvivor]

Originally Posted by xsports33
i haven't checked the fluids yet, but i found that where the front driveshaft meets the transfer case there is a little bit of play. not much, but a little. none at any of the other connection points.

if it is a pinion bearing will it leave metal debris in the fluid?


Both of those will cause a vibration, but not this noise. I've had vehicles with lose TCase output bearings and bad pinion bearings.

However, you mention it doesn't do it in 4wd. I wonder if the supercharger is causing vacuum issues with the vacuum hubs (I believe the GM trucks have vacuum hubs) and some sort of vacuum actuation inside the transfer case.

It almost sounds like the vacuum hubs are half engaging and that's the splines grinding or something long those lines.

 

[xsports33]

there is about 60,000 miles on the truck. that's correct, 60K on a truck that is 13 years old. i rarely drive it, it's my "play toy"

 

[xsports33]

i pulled the transfer case fluid. it looked perfect and nothing on the magnet. i then pulled the front diff and this is what i found. does that look abnormal? too much shavings?

 

[MrMoody]

Front diff seems unlikely. I've heard a rear driveshaft make a noise something like that with a loose bushing or u-joint, but never that severe and it was affected by throttle position change either way as the slack was taken up, also you could definitely tell it was in the rear and not under the hood. Still might pay to wiggle the rear shaft and see how it looks.

Not saying it's your problem, but read this thread, he said his t-case fluid was clean but turned out to be the problem anyway:
https://www.coloradofans.com/forums...-metal-scraping-noise-when-coasting.html

You may have to do as he did and get the truck in the air and try to reproduce it so you can tell where it's coming from. Be careful of spinning parts.

 

[Astro14]

That drain plug looks abnormal to me... a big pile o' shavings on it...

 

[DGXR]

Drain plug looks abnormal to me also. Fine particles (aka goop) indicate normal wear. Those are not fine particles, those are shavings. Not normal.
Also it looks really dark, like the fluid is long overdue for a service.