when I take off, it takes awhile for it to go into 2nd gear only in the begining. after it warms up but it also feels like my truck has loss of power also

Is the fluid level good. When was the last time the filter and fluid was changed.

are you talking about the oil and oil filter

I believe knfenimore is referring to transmission fluid. More information about the vehicle would also help, such as year, 2wd or 4wd, mileage, engine option, transmission model (if you know; probably 4L60E if I had to guess), and any other pertinent information you can think of to provide.

2004 2wd 87000 miles 4.3L not sure when transmission fluid was changed

If you don’t know when it was changed, that might be an indicator as to why it is doing it. In any case have it checked by someone who knows transmission (NOT A CHAIN SHOP!). If you can salvage the transmission, be sure to change to fluid and have the filter cleaned/replaced at the same time.