1991 420SEL ABS/ASR system question.
 

ABS was standard in all 1991 US models. ASR was a factory option.

Sixto
83 300SD
98 E320 wagon

That early system is nothing but trouble and not even remotely worth the trouble. It has no diagnostics built in and when they go on the fritz it can be an expensive nightmare to fix. All to have a computer to decide better when you press the gas pedal.

Agreed....why would you want to add the nightmare that is ASR to your car? If you're worried about the ass end sliding around, change your driving style!

See if WaveTrac or Quaife make a LSD that fits your case.

Sixto
83 300SD
98 E320 wagon

I retrofitted ASR to my 99.5 Jetta. On that car it was a simple swap of the combined computer / hydraulic unit. No wiring changes, it already has an electronic throttle and 4 brake hydraulic lines.

On your 560 it would require a complete throttle linkage, throttle body, electronic throttle wiring harness, speedometer, ASR / Cruise Control computer, ABS unit, ASR pressure accumulator, rear hard brake lines, ABS wiring harness, rear ABS sensors, differential, and rear brake pad swap. Oh, and I think the rear axles too?

I'd sooner just get the LSD your 560 came with rebuilt.

-J