Well, I destroyed my first diff within months of installing my own lock right locker.  Its a manual transmission 1994 4door with 30" tires.  It developed a loud whine so I bought a used diff and installed the lock right in that about 6 months ago.  It worked great and ran quiet until a few weeks ago.  Now it makes noise.  Every couple hundred feet it makes a noise like there are a bunch of marbles rolling around in it.  I drained the fluid and there aren't any chunks of metal.  If I put my finger in the fill plug and touch the carrier bearing while my buddy kicks the right rear tire, I can feel it moving a little while making a rattling sound.  I followed a step by step procedure on installing the lock right the best I can. 
Should I try to have the diff professionally rebuilt or just find another one?  It looks like I better have the lock tight professionally installed this time.  Do most transmission shops do this type of work?  Is the lock right really hard on the diff just by nature? 

Thanks

Jon

Correctly setting up a ring & pinion takes specialized tools & experience, it's also a "get-it-right-the-first-time" deal - if you don't, by the time you know it's not right, you've already destroyed the gears.

Lockright would like you to think that anyone can install their locker, but, because you have to remove the differential case from the third member, there's always a possibility that you don't get the mesh correct on reassembly.

The loud whine of the first differential sounds like the gears may have been incorrectly set up, there's insufficient information about the second failure to make any suggestions as to what failed - you'll need to at least remove the third member to know whether a rebuild is even possible, and that's also the point at which you'll know if the failure relates to your installation of the lockright - maybe you got it right and something else failed.

Technically speaking, when you install a lockright, you have to remove the differential - once the gears come out, there's no longer any differential action, so no, the lockright is not hard on diffs, but, lockers generally load the axles to a greater extent, and depending on the terrain you're driving, you can end up applying 100% of the available torque through a single axle shaft, and that becomes the point of failure.

Well, I destroyed my first diff within months of installing my own lock right locker.  Its a manual transmission 1994 4door with 30" tires.  It developed a loud whine so I bought a used diff and installed the lock right in that about 6 months ago.  It worked great and ran quiet until a few weeks ago.  Now it makes noise.  Every couple hundred feet it makes a noise like there are a bunch of marbles rolling around in it.  I drained the fluid and there aren't any chunks of metal.  If I put my finger in the fill plug and touch the carrier bearing while my buddy kicks the right rear tire, I can feel it moving a little while making a rattling sound.  I followed a step by step procedure on installing the lock right the best I can. 
Should I try to have the diff professionally rebuilt or just find another one?  It looks like I better have the lock tight professionally installed this time.  Do most transmission shops do this type of work?  Is the lock right really hard on the diff just by nature? 

Thanks

Jon

I'm thinking if your lock right was the main issue... then you would have, at the least, pieces and parts of the eight lock right springs collected on your drain plug.  In addition, if your lock right springs had failed (through breaking or getting chewed up) then you shouldn't have any drive to either of  your rear axles. 

Did you lock tight the bolts on the carrier bearing caps and ring gear and torque them correctly during the lock right install?  There should be a very slight movement to the ring gear but the carrier bearings shouldn't be loose.   I'm thinking if you have excessive play in your diff it could also be worn carrier bearings.  After all, we're talking about a '94 vehicle to start with, then you state you bought a used diff and I'm guessing you have no history on the "new" used diff.  It could have had bad (old, worn) carrier bearings in it when you received it.

Low Range did sell their diff rebuild kits for around $100-$110.  Fordem is correct though, rebuilding the diff does require some special tools like an inch pound torque wrench for setting the correct drag on the new pinion bearings.  In addition, you need a strong jig of some design to hold the diff when you start tightening down the pinion bearing to compress the crush sleeve to achieve the correct pinion drag OR a mighty bench vise to hold the lip. Getting the correct shim on your pinion shouldn't be an issue if your ring and pinion are not destroyed. Should be able to re-use the same pinion shim to rebuild it IF your pinion and ring gear are not damaged.

What got destroyed on your original diff?