Transmission whine/grind when rpms drop below 2000rpm

[bigskyboarder]

I'm trying to buy a 2004 Silverado 1500hd with the 6.0 and 4l80e. When test driving the transmission would shift through all the gears fine but if you let off the gas as soon as the rpms hit 2000 they would drop to 1500 to 1000 and there would be a loud grind/whine until you tapped the gas again. I'm assuming it's the transmission, maybe the torque converter. Any help would be great so I can figure out if the transmission would have to be rebuilt or if it's something simpler to fix

[Kimberly Prescott]

I have a similar issue with my 2000 Silverado (1500, LS,  5.3, 4x4) A whine starts at 20-30 mph, gets higher pitch at higher speeds. A shudder when letting off gas pedal from right front, and a rotating, grinding sound as speed decreases, from under cab.  Also a clunk when shifting into R or D from Park but not N.  Have replaced  rear ujoint, serviced rear differential. Front ujoint looked good, no binding good rotation. I have had a dozen different opinions, but not from a Chevy/GM owner.  Appreciate any help.

Edited May 5, 2020 by Kimberly Prescott
Added truck information

[Silverado/Sierra guy]

Sounds to me like it’s the torque converter going out.