When hard accelerating gears slips rpms jump around til it goes into gear when still hard accelerating about 80km/h the vehicle starts to shake and rpms jump from 2500 about 5000, no smell or anything.. But when i slowly go to highway speeds nothing happens its all fine. Recently did plugs oil and tranny filter change, oh yea and 1 code p0155 i think its a 02 senser

 

Sounds like you discovered the 4L60e Achillies Heel. 3rd and 4th gear clutches are smoked. Time to rebuild or replace. If it is doing it at any speeds under 80km/hr then the burnt/damaged clutch materials are probably distributed through the system and will eventually lead to complete failure. As long as you are 100% sure you got enough fluid put in after the filter change, that could have been the time when there was a loss in pressure. The 3rd and 4th gear clutches are not forgiving and will go out at the slightest loss in fluid pressure.
Welcome to the forum.

 

It runs fine when i dont press the pedal hard no rpm jumping and it goes passed 80km/h i can go 120km/h no problem if i take it slowly

 

And if i were to get a different used transmission would any 4l60e 4x4 4sp work with my 03 blazer

 

Well that sort of changes things. I suppose just make sure you have the proper fluid level. At the full mark on the dipstick with the vehicle running and at operating temperature.
If you are looking for a replacement you would want a '98-07. But since you said it works fine otherwise there has to be something else going on.

 

It is still the 3 to 4 clutches gone. Just not as bad under a light load. They may have just enough material left to work but that wont last very much longer.