I need help! My 2003 blazer will shift all the way down too first but will only shift up into 3rd then its stuck and wont go any further. I have to shut the engine off and put the E brake on and climb underneath and manually put it in park. So it shifts down fine just doesnt want to shift all the way up... What could it be? Btw its 4wd

 

You may need to have someone watch the cable from under the truck as the shift lever is moved through its range of motion from park to 1 and back. I suspect that there is a problem with the cable, specifically where the cable itself attaches to the bracket at the side of the transmission. The cable may be slipping out of this bracket that it should be locked into. It may be possible to find a way to get the cable to stay put once you figure out what it is doing. If what I think is occurring is true, the little tabs that are supposed to kick out and hold the fixed end of the cable outer sheath in the bracket are deformed or broken and not doing their intended task.

This thread has the appropriate link to show you how to get things adjusted properly once you get the new cable installed if you end up going that route.
Wont go into park! Everything else OK.