2004 Chevy Silverado z-71 shifting rough?

[David]

Has about 127,000 miles on it (mostly highway). While shifting from 1st to 2nd, it sometimes delays for a second or two and then kinda clunks into gear. Sometimes it shifts smooth and normal.

It is coming due for a transmission fluid change, but do you think that will be enough to fix the problem or is this gonna be something more serious and expensive ?
Forgot to mention that it shifts fine in higher gears. The fluid level is full. Why would the higher gears not shift rough along with the lower gears?

 

[Tyler P]

ya somethings definitly wrong with the transmission. change the fluid as soon as possible but it might be something other than that

 

[matt]

I would flush it and try high performance oil. Your truck should have a check engine light if it senses a slip in the transmission so you might get lucky with a transmission oil change. Good luck!