On my 1988 420SEL the rear end is starting to squeak at low speeds under 25 is most audible, and fades away at 30 mph. Now I heard that you can lubricate the rear end by punkcing small holes in the rubber parts but I'm not too keen on doing that untested as I'm sure Mercedes sealed those things up pretty tight for a reason. Yet, have anyone tried that method yet and what was the result, good or bad.

Plus on a side note, what is the fastest anyone gotten a 420SEL up to?

In germany Autobahn I gotten my American spec 560SEL up to 150mph (with proper rated tires) and cruised there a while before having to slow down due to traffic. I think it could go at least 155mph.