FredR

Bob,

Some interesting inputs but nothing in the direction of explaining why jumping the kickdown switch would cause damage beyond normal wear and tear.

Charles Schmid

I just wanted to get a better idea of ​​how everything works. because nothing is original with me, I have separate itb's so I also had to adjust my throttle cable. as a result, the bowden cable no longer works properly. it is also intended to increase the fun factor.

Charles Schmid

Ninespub

I'm waaaay out of my class with the mensa (928 chapter) group of Greg, Dr. Bob and FredR, but wasn't there some sort of trick mod when you upgraded the spring set to eliminate "flare" in the MB transmission where if you reversed a particular plastic piston(??) in the kit, it would automaticly start in first gear? My memory is hazy as it was done years ago when i had a trans filter & fluid change, along with MM, OPG and other stuff done. Seemed like a simple action that was documented in the instructions that came with the Factory (Porsche & MB) authorized/recommended part.

FredR

Like you I have some piece of info in my hazy memory banks that goes something along the lines you have written about.

The simple fact is that the shift action is not controlled by a microprocessor but by hydraulic logic supported by external inputs that help the logic. MB could just have easily have engineered the system to start out in first gear and for sure it was not configured that way to protect the system from mechanical damage as if they did, no one would puchase a piece of junk like that. What they did do was build features into the system to defeat the basic design logic so that those who so wanted to take off in first could do so. There were no useage limits imposed as to how often the driver could do this. So, perfectly plausible that there are ways to do this and as I am concerned that mods I implemented do just that. I have not seen or heard of any logical reason to support why doing what I do will in any way corrupt the harshness of the shift- that is the challenge I put down given my ongoing technical interest to learn more about these things.

As with any piece of mechanical kit the harder one uses it the quicker it will wear but the real point of interest is not "whether it will wear out" it is ""how much quicker will it wear out".

Ninespub

I found it (Kinda) It's called the "K-1 Accumulator Spring Kit", no other info at this time.

Gary Knox

I owned an MB 560SEC for about 20 years - '96 to '16 - and the 1st gear start vs 2nd gear start was common discussion topic there (same 4 spd automatic). A company named Berg Werks made a 'kit' that was apparently fairly easy to install, but it is NLA. Here is a link to some discussion of this 1st gear module start on an MB forum. It includes a circuit diagram for the kick down, and also an example of a privately made module.

https://www.benzworld.org/threads/di...odule.2937209/

There may be other MB Forums with similar discussions as well. I didn't search any further than the linked forum.

Hope this might be helpful.

Gary

PS: A bit more searching and I found this Forum page: https://forums.mbclub.co.uk/threads/...-module.62828/ Scroll down to post #6. There is an original MB module used in the early 126 chassis cars with the 3.8 liter engine and in the Euro 5 liter engine cars that produces a 1st gear start.

Look at post #6 on this link for the wiring connections on that MB module: http://www.peachparts.com/shopforum/...5-41-32-a.html

FredR

I have a feeling that kit was intended to cure a common problem with shifts from 2nd to 3rd wherein flare was a problem. Maybe it had a secondary consequence?

FredR

Gary,

A quick squint at the link suggests that the kit is a PLC that the owner programmes to his taste and that gives an output to the final element that enforces the action. Seems to me it is probably the same final action as the B gate option [did you have that on your 560?] and I suspect that is a switch that does the same thing as the kick down by-pass switch- a solenoid valve that triggers a first gear selection action as the final initiation element- no new kit per se..

Gary Knox

Fred,

My SEC did not have the B (braking for downhill) switch.

Gary

FredR

Gary,

I understand the B option was not available in all markets but which ones I have no clue. My guess is that it would be available in the States. Friend of mone had a superb example with the B option but never actually found out what final element triggered the shift process- I assume it might have been triggered by the kick down actuator as I cannot visualise anything else on the plot that can achieve the same effect.

Gary Knox

Fred et al,,

The MB component that did the 1st gear start when the B switch was activated is part number 002 545 41 32. The MB Forums have instructions on which pins need to be connected where in order to use the component with MB's that don't have the B switch. There are only 3 or maybe 4 wires needed: 12 V+, ground (earth), connection to the kickdown switch and a speed sensor such as the one that goes to the radio for increased amplification as the speed is increased. Here's a picture of it taken from an eBay listing. Guaranteed used ones seem to run from $30 to $50.:
If memory serves me right - based on Deutsche language course I took 65 years ago - the name on it as relating to automobiles means 'speed gear change'.

If I buy another 928 Automatic, I'll look into seeing if it will function with a 928 as a small project!

Cheers,

Gary

Schocki

Geschwindigkeitsschalter means "speed switch"

FredR

Well that piece of kit looks like something that fits inside the cabin so my logic tells me it is a "logic solver" of some simple kind. Voltage in plus a couple of signals derives an output that presumably goes to something on the gearbox so what can that something be? As I am aware there is only one thing that is actuated externally on the gearbox- the kick down solenoid- so maybe MB wanted a couple of conditions satisifed to actuate it- speed below a certain setpoint [for instance]?

Bottom line- something external has to act on the gearbox to effect a change of some kind. Whatever it is, it has to be something relatively simple or major changes to the box would be needed.

dr bob

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.

I have the original gear lever handle in my someday-projects bin on my workbay desk. It's suffered the classic blowout of the mounting screw holes, and there's a sleeve already made to insert to make it newer/stronger. It's tempting to add a momentary-contact switch inside the handle, actuated by the release button. Instant hidden PKS, for getting that early downshift. I get to push that button to get the lever from D to 3 anyway, but maybe avoid having to actually move the lever to go down a gear a little sooner. It's a function I very seldom wish I had available. Might have to work with Nate to get a 3D-printed factory handle going, with room for that switch and for the metal sleeve in the bottom.