5R55S 1-2 shift buzz

[Black Dynomite]

Hi all
On the 1-2 shift, i hear a quiet buzz come from under the vehicle, right between the front seats. I also get the same buzz when braking to a stop, assuming this is the shift back to 1. It only seems to happen when the vehicle is cold, once warmed up, I dont notice it.
The buzz is quiet, only last 1/4 second (if that), it so quiet, its hard to hear above normal conversation.
Any ideas what could be wrong here? Assuming a tranny issue, but exactly what?
Thanks in advance

 

[Josef161]

I guess it is caused by debris in our transmission fluid. That debris can claugh passages in the valve body and shift solenoids (once the transmission fluid gets warm it's velocity decreases and it can for better trough those narrow passages). If it really bothers you you could chance the solenoid pack first and if that doesn't work the valve body. However, if i were you i would perform a fluid and filter replacement, that could clear the passages a little bit and it will make sure that the symptoms won't get worse.