I use a mechanic that will, if at all possible, re-boot the axle as opposed to replacing it. His argument is that the "new axle" is not as well manufactured as the original ones installed at the factory by MB.
As all 4 of my axle boots are cracked on my 84 300D, I am going to have him reboot them before they rip. The cost for this job is estimated at 800.00, includes all new boots, re-crimped with the factory tool, new diff. fluid and a complete tear down and rebuild of the original axle.

I hope it's worth it.

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1984 300D