This car has an ABS/ASR system. My 1991 560SEL only has ABS as best I can tell. Did Mercedes install the combination ABS/ASR only on certain cars? or was it an option at purchase?

https://www.youtube.com/watch?v=sKTaPPO5i9E

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

Sixto
83 300SD
98 E320 wagon

Is it possible to retrofit a 1991 560SEL with ASR??

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!

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

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

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.