J spaulding

I haven't been able to find out all of what ASR does but my VIN decoding said that this car has ASR as well as Positraction. Does anybody know if 129's came with Positraction? It gets a little more confusing when I tested by moving one rear wheel and the other one turns in the opposite direction (non positraction).

SRHsl600

My benz was never promoted as having "positraction". Got a big engine "63 SS" that has it! The benz system is miles ahead of the old GM back axle system!

cliffyk

"Positraction" is GM's brand name for its clutch-type limited slip differential; Ford calls it "Traction-lock"; Chrysler calls it "Powertrax" IIRC--so, no R129 ever had positraction--nor any other form of LSD in the "base" (non-AMG, etc) models.

"ASR" is Acceration Slip Regulation, I.e. ABS/ECU based traction control...

markesys

The R129s ('96 through '98, anyway) do implement a "PosiTraction"-like function, using the same hardware as the ASR. The way it works is when you turn off the ASR (so that the yellow triangle is lit up on the speedometer), the system still monitors the speed of the rear wheels. If it sees one spinning significantly more rapidly than the other, it applies the rear brake to that side only, so that the non-slipping wheel still gets most of the torque.

You can easily try this out by finding an area where there's a dirt strip that you can put one side of the car on. Do this, turn off the ASR, then punch it. In a car with no "PosiTraction", the rear wheel on the dirt will spin like crazy, and you'll have very little acceleration. In these cars, you might end up lighting up the pavement-side tire a bit, but generally the car will move out pretty well.

I sometimes use this mode when I know that I'll need to "leap out" from a side street. Sometimes the ASR gets a bit over-active and throttles everything back, at exactly the time I need acceleration the most.
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Mark Moulding