Tranny problem or ??????

Hey I have a 1991 Sierra with a 305 and I don't know what kind of tranny I assume it's a 700r4.
My problem is that it will shift from 1st to 2nd with no problems but when it gets to the point it should shift from 2nd to 3rd it doesn't it just will rev really high untill I take my foot off the accelerator and then it will shift. It will then shift to overdrive smoothly but once it is in over drive the truck almost seems to very lightly surge the rpms slightly up and down.
I have read on here about changing the fuel filter and will be doing that on the weekend. Any other advice would be great
thanks

you will need to get this to a transmission repair place. what is happening is there are a coulpe of check valves inside that use a ball and seat. and what is happening is the seat is worn and the trans fluid is bleeding past the check ball and not allowing the trans to properly upshift. if this is a 700r4 trans, there are alot of modifications that are for that trans and removing the check ball valves and putting a plug in place of them is one of the mods that were made to that trans by rebuilders.
had the same thing happen to my 86 s-10 that i use to have.

If you're not willing to pay for the rebuild of the tranny or just need some time to get the money together, try a tranny conditioner fluid. I have used some in a 94 grand am my wife drives for the past 4 years. It started not shifting into gears so I figured I'd give the conditioner a shot. Just being cheap at the time. Well, as stated, I've been using it for 4 years now and it's still going. The tranny is getting worse but it bought me 4 years of not listening to the wife complain about her car. I will replace the tranny when it dies.

i had the same problem in my gmc 2500 i just changed the filter transmission filter and then filled it with b and m tranny fluid and lucas transmision fix and it works perfect now and it was about $40