Unusual Transmission Issues (6speed AT)

Hey y’all.

I’ve been running into some unusual transmission behavior on my 2010 6speed transmission. I’m sitting at 240,000 miles and only owned the truck a year. When I bought it, it shifted great.

I’ve already worked with the transmission a bit because of those cooling lines running to the radiator rusting through. I unfortunately ran the truck about 2.5 quarts low before I realized and replaced the lines and did the drain and fill with some Valvoline max life and Lubegard. I did the drain and fill correctly. I have done 3 drain and fills (one when I got it, and 2 in the process of dealing with the radiator line).

The transmission shifted great for a while. However since the change my shifts have slowly gotten harder. My first 3 shifts tend to clunk slightly while in drive. The rpm’s also tend to be higher for a shift to occur (around 2.5 thousand rpm’s… I have a light foot) but there is little to no slipping sensation. They are smoother when driving in “4.” Simply, the transmission just feels unhappy with having more hard, clunking shifts than it used to… I didn’t expect that after a drain and fill.

Now, after I have stopped at a light, the truck will occasionally lurch forward against the brakes as if it was just put in drive.

I haven’t been able to pull any codes when I’ve taken it to an AutoZone. Should I invest in a scanner to get live data while driving?

Am I overthinking the transmissions behavior?

 

That's normal. My 07 has done it since new. Only on rare occasions do I notice it.