My recently purchased '05 Silverado 1500 has no problem shifting except between 2nd and 3rd.
On upshifts, it shifts out of second, then there is a small flare, then it tries to engage 3rd, then it flares again, then it engages 3rd. It takes about a second and it's very consistent.
On downshifts, it acts pretty similarly but it essentially acts like it's in neutral for .5 seconds. If I'm in 3rd or 4th and I depress the accelerator, revs out to 4k or 5k and then roughly engages 2nd.
Otherwise it's perfect. No slipping, normal shifts, normal idle behavior, reverse works well, no noises or smells. The transmission fluid level and color is fine.
I did some googling and narrowed it down to the computer, valve body, or solenoid which is basically not narrowed at all.
Has anyone else had and fixed this problem?