what model did you pull the 2.47 diff from?any mods needed to make it work?
speedo swap too?what are you rpm engine speed at 60mph?

Oh not at all, a bomb would likely destroy a diff

As will neglecting to change fluid regularly. Regardless of recommended service interval, I change diff fluid yearly. It's cheap and easy so why skip it?

And your indie can put it any way he wants, gears don't just "wear out" without a reason. Adequately lubricated diffs with gear lash set properly and no bearing play should outlast nearly every other part on a car/truck that just sees commuter duty.

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'84 300D
'97 Jeep XJ lots of mods
'01 Subaru Forester

Just replaced diff oil with Amsoil 80/90 So far so good!