Weird metal piece included with the new truetrac diff

DaisyDart said

Hello everyone,
After recently purchasing a detroit truetrac diff, i went thru the manual and everything but cannot find what this metal piece is for?? I'm hoping someone on this forum has experience with these diffs and can help me out with identifying its purpose. Its not listed anywhere in the installation guide.
Thanks!

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When I bought my differential I got one of those as well. What you are supposed to do is bolt your rear axles into the rear end and see if you can slip the plug between the axle ends. It's purpose is to provide a means of checking axle clearance to prevent crushing the center section internals. If the fit is too high you are supposed to shave off the ends of you axles until they plug fits.