Transmission Flare/Grinding

[DenaliHD66]

Alright, so 107,000 miles on the ticker, and a PCM tune for level 2. Last transmission flush was a few thousand miles ago. Okay, so now that we have that said, I notice that when I floor the gas, the transmission makes a grinding sound at the very top end. Is this typical, or is this bad? Its more of a whining noise than a grinding noise, but there is some vibration coming from the transmission when the RPM's are way up. It has been going on a while, but hasn't affected performance, so I've pretty much let it go.

This morning, I was cruising down a straight road going about 40 mph under very light throttle, just keeping pace with the car in front of me, and then my speedometer suddenly revs up, as did my tach, and my SES light flashed, then a second later they go back to where they were. Assuming this was a transmission flare? Never happened before, but made me wonder if something is starting to go. Where to start?

Also, ever since I got my 265/65/17 tires, my transmission seems to do a bit more hunting in the 3-4 gears, and is quicker to downshift under light throttle, and sometimes doesn't seem to want to make up its mind to shift into overdrive. Is this typical because the tires are 1" larger in diameter than stock, or with all the information I've put together indicating something wrong with my transmission?

 

[The_Roadie]

I'd start by researching local trusted and competent tranny shops for an accurate diagnosis using professional tools. Forum experiences are great, but you can get too-cautious AND too-alarmist advice on the web. Neither of which serve you well compared to somebody with hands-on YOUR hardware.