I installed a Sears screwdrive garage door opener about 18 months ago and
it's worked great up until last week. Symptons were that the screw drive
made a lot of noise and failed to pull the door up. I could push the
'connector car' up and down the track so assumed the internal mechanism that
ride on the screw threads was shot.

I order a replacement and I installed it tonight (the old one was obviously
stripped) however the opener has developed or also had a different problem.
When on and disengaged from the door the screw itself is making a heck of a
noise - it is almost like it is lose in it's tunnel and is 'thrashing
around'. I disassembled the support beam (it is made up of 3 pieces) and
looked at the screw - which seems fine. It runs inside a plastic tunnel -
which also looks fine. I've checked the beam and it seem straight and true.
Any thoughts are appreciated.