my first semi build (dump)

[chaseracer]

not much new to post, bit frustrated. been working on lift system, based on a screw drive type setup, with a sliding block between two rails with a rod attached to it and the box. I tried pushing and pulling on the block. but the box will not lift, it just binds up, feels like it wants to rip the box off, unless I lift the box up a inch and it goes up no problem, can't figure out what the problem is?