Growling noise

[FD5]

When driving down the interstate my 89 will make a growling noise if I let off the accellerator. The noise goes away if I step on the accellerator and maintain a steady speed. Any ideas of what the problem might be?

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1995 2500, SLT Laramie, Xcab, auto, 3. 54, stock plate forward, 237K, Amsoiled throughout, dual by-pass filter, muffler and cat fell off, if you find them, there yours!!
1989 250, Cummins, auto, stock, work truck, 190K, soon to be Amsoiled
1967 Coronet 440, Steve Thomas built 360, auto, 2. 94, factory A/C, am radio, FAST!!!and is FOR SALE $5,500
1987 Celica GT convertible, auto, 67K
1989 Holiday Rambler Aluma-lite travel trailer
Amsoil Dealer

 

[Scot]

Sounds like early stages of u-joint or loose yokes to me.

 

[Caltruck]

Ditto on the u-joints or carrier bearing. Most likely u-joints, recommend replacing all three, not just the bad one.