Replicator 2, horrible noise and shifting along X

Hi all,

I have had my Replicator 2 for quite a long time, and granted it is a very old machine now, but I have serviced it well and kept it in good condition. Just today it started giving me issues, where it makes a horrible grinding noise and the x axis shifts. It's always the X axis, and it always shifts to the right. At first I thought my linear bearings (an upgrade I did several months ago) were binding, even though the extruder can be moved very freely and smoothly by hand, so I replaced them with the stock bushings, however the problem still persists and if not worse.

Other things I have done;

> Swapped X/Y stepper motors to rule out stepper motor fault (still only happens in X, so not the motors)
> Swapped X/Y stepper drivers to rule out driver fault (again still only happens in X, so not drivers)
> Made sure drive pulley is very tight on the shaft, and belt is well tensioned.

I'm at a loss, and would really appreciate some help please!

Video: https://youtu.be/zP5-wSvNlR8 (yes, I violently pushed it since it was getting too close to the end stop lol)

I recently had a problem with my up-until-now dead reliable QIDI Tech 1 which sounded like yours (pun intended). I tried many of the same things you did, all to no avail. Finally, I got out my hex wrench kit and tightened every fastener I could find, including the case connector cap screws. I found that the two cap screws holding the extruder to the carriage were slightly loose, as were the cap screws holding the extruders to the stepper motors. Not noticeably loose in operation, but at least 1/2-1/4 turn loose when tightened. After this procedure, the noise stopped and my prints became better looking. My next task will be to revisit all of the fasteners with a tiny drop of blue Locktite on each to prevent recurrence of the problem. If you try this, be sure to use the blue version, which can be removed later with a wrench...the red version is essentially permanent in this application as it takes fairly high heat to make it release. Good luck!

Could be the cable from the driver to the stepper. I have had similar things happening on a couple of my printers after prolonged use (X or Y steppers, or extruder steppers) which were resolved by exchanging the cabling. After so many rapid movements, the cores in the cables seem to get compromised at some bending point.