Rough shifting

I've noticed my truck periodically shifts rough and shutters mainly from 1st to 2nd and slightly from 2nd to 3rd. It does this after it's warmed up and been driven. It seems to do this more after driving on the highway at higher speeds. It doesn't do this regularly and is not predictable - just changes from day to day. Over all it runs really good but I've noticed a decrease in my gas mileage lately. It doesn't shutter or clunk into gear from park, doesn't idle rough and has the right amount of tranny fluid in it. I had the fluid and filter changed a few months ago with not much effect on this. Am I just being paranoid or is my truck trying to tell me something?!

I had a similar prob. on my 97 Sierra after going into overdrive,
it would slam into 2nd real hard and not go back into overdrive
until I turned it off for a second & restarted. After researching,
found out is common for valve body guides to wear & computer
senses slippage and messes with the pressure. There are kits
available to bore & replace valve body guide & valve but in my
case, I needed a rebuild & new TC. I am told the constant slamming
can bust things & driving without overdrive will burn TC & bad miliage.
Often you will also get an engine code as I did. Google
"GM trans slippage" or I think it's code "P1780" and read all about it.

Have you tried changing the fluid and filter on the transmission. I do mine about every 10-15,000 miles (once a year). Every time I do it, I can notice the difference. The tranny will shift smoother

Try a throttle positioning sensor. Was the problem on my 93 model 2-wheel.