1994 suburban transmission problem

So the other day I was driving to my storage locker about 30 miles away. All of a sudden my rpms would shoot up to 2000 rpms then back down to 1500 . Slowly they would go up higher every time. On my way back I was about 2 miles away and I lost 3rd and 4th a presume. I would be going 20-25 and it felt like it would be shifting up to third but would shift down to 2nd running 3500 rpms. I had to go 20 the rest of the time. Finally I got home and realized my dipstick tube wasn't in the tranny and must have lost oil. So I got it back in and added more. Thought it was the filter and oil so dropped the pan and replaced it. Still nothing. Thoughts?

So the other day I was driving to my storage locker about 30 miles away. All of a sudden my rpms would shoot up to 2000 rpms then back down to 1500 . Slowly they would go up higher every time. On my way back I was about 2 miles away and I lost 3rd and 4th a presume. I would be going 20-25 and it felt like it would be shifting up to third but would shift down to 2nd running 3500 rpms. I had to go 20 the rest of the time. Finally I got home and realized my dipstick tube wasn't in the tranny and must have lost oil. So I got it back in and added more. Thought it was the filter and oil so dropped the pan and replaced it. Still nothing. Thoughts?

time to get another vehicle. not worth paying the cost to fix this old.

What about adjusting the trans band? Or solenoid for 3-4?