Downshifting a W126

I frequently downshift my '88 420SEL into 2nd gear to slow down from about 40-50mph. Does this cause any extra wear on the tranmission or the engine?
The reason I do this is because the brake control arm bushings (I think that's what my mechanic said they're called) are worn, and it feels like my rotors are warped when I brake at higher speeds, and sometimes makes the steering wheel vibrate quite a bit. I was told it'd be a $300 job to replace the bushings, and I'd rather wait untill it's absolutely neccisary than waste that much money now.