Shifting the tranny manually had no affect on the overall problem, it shifted into 2nd on its own, it was so smooth I didnt notice it the first time. The previous owner stated that it had a recent fluid change and mentioned no overhaul or other mechanical problems with the transmission, he only stated that.."sometimes it shifts and sometimes it dosent".
Mentioning the dipstick. I made that remark because at looking at the hash marks on the dipstick and looking at where the fluid actually read, I would guess that it was a Qt. to full.
I took the blazer out for another test run and I paid closer attention to the shift into second, it shifted smooth but still didnt shift into third. I slowed back down allowing it to downshift back into first and this time instead of creeping into a shift a gave it the gas and at the point where it should have shifted into third it almost felt as if it fell into neutral and the RPM's shot up to around 5k.
Hopefully this info helps...