My 8 1/4 doesn't make any ugly noises when put into gear, but then, I was the last one to touch it. Rebuilding the diff is not difficult, but setting up gears is an art. If you do not need to replace the ring and pinion, then you can do it yourself, as long as you follow something like the factory service procedures. The most important tool for this is a dial indicator, to set the backlash correctly. If you replace the bearings, use only TIMKEN! Timken bearings are what should be in there already, and the tolerances are excellent. Replacing the bearings becomes a simple act, with no fuss besides resetting the proper backlash on the gears. Don't forget to reinstall the shim in the drive pinion where it came out, and that you need a BIG breaker bar or cheater on your ratchet, in order to properly crush the crush sleeve under the companion flange (yoke). I broke a sweat during that part of the installation, believe me! Before deciding to tackle this, read the procedures, and you will know for sure if you want to do it. Also, the 8 1/4" is the little diff that could! Much stouter than many people will have you believe. Mine has withstood the tests of both time, and torque.
