928 S4 91 start first gear
03-08-2021, 12:21 PM
#46
Rennlist Member
That looks amazingly like the module that we tried to fit to my '89 car over 20 years ago now, by a then-local MB specialist. We got the module itself to work just fine, but supplying current to the kickdown solenoid wasn't enough to force a first-gear start every time from stop in my car. It still required a stab at the skinny pedal on launch, and not much less than it takes without the module. Yes, the control pressure dropped, but not enough without the TV cable dropping it further. The package we made up was configured to live in the spare wheel well where power (via the fuel pump circuit), speedo pulses, gear selector position, and existing kickdown solenoid wiring were all readily accessible. It's certainly possible that my particular car is/was somehow 'special', as others with the parallel kickdown switch mod seem to be able to force first-gear launches. It's certainly easy enough to test on your car with a simple jumper wire at the pedal switch.
I'm not unconvinced that you could get virtually all the response expected from a PKS with some fiddling with the TV cable adjustment and perhaps a slight ratio change at the throttle bellcrank in the engine bay.
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I'm not unconvinced that you could get virtually all the response expected from a PKS with some fiddling with the TV cable adjustment and perhaps a slight ratio change at the throttle bellcrank in the engine bay.
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The only way the shift characteristics can be modified is to change the hydraulics. This is what happens when the kick down solenoid is engaged and it is what happens when the kick down cable is tightened. There is nothing magical about this and the end result is perfectly drivable- no odd behaviours, changes when I want it, no hang ups in lower gears- plain and simple it behaves like a manual without the stick- shifts up are induced by backing off the throttle. It is difficult to spin the wheels but then I have the PSD system and wide, quality rubber sticking the wheels to the deck as it were- stock rubber might be more 'exciting".
I would still like to see theories as to why such mods might cause damage to the tranny- from my point of view it is doing what it was deisgned to do with modified programming..
Last edited by FredR; 03-08-2021 at 12:22 PM.
03-08-2021, 03:02 PM
#47
Chronic Tool Dropper
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Hi Fred --
My thinking is that the higher-RPM upshifts are inherently sharper/higher impact on plates/disks and baskets than my lazy shifts upshifts at 1500 RPM rolling in traffic. With higher low-load manifold pressure, the modulator allows softer shifts too. Also fewer downshifts so fewer upshifts. That's my story....
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My thinking is that the higher-RPM upshifts are inherently sharper/higher impact on plates/disks and baskets than my lazy shifts upshifts at 1500 RPM rolling in traffic. With higher low-load manifold pressure, the modulator allows softer shifts too. Also fewer downshifts so fewer upshifts. That's my story....
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