Firstbornlast2dieb4u

So my 87 gl transmission won't shift into 3rd gear at all . It will automatically shift from 1st to 2nd but nothing higher. The rooms just ride but it didn't gain speed. I can shift from first to second with no problems then when shifted into drive the Rpms just rise.. so Park reverse neutral 1st and 2nd Work just fine.... What could be the problem. ? Can anyone help ?