jwyatt8171

Messing around i found a switch under the gas pedal. What is this?
It doesnt look like the arm reaches it when/if the pedal is to the metal.

Leon Speed

Transmission kick-down switch. The bottom of the gas pedal bracket should depress the switch at full travel.

Big Dave

When activated, the switch will force the transmission into the lowest gear possible without redlining. Some folks (including me) have spliced in a switch that can activate this feature without flooring the accelerator. There's actually an adjustment point under the accelerator if it's not reaching far enough to trip the switch when the pedal is floored.

jwyatt8171

That makes sense. I wondered why when lumbering along at 2800-3300 rpm I would kick it and wouldn't down shift. Had to do it manually.
Guess I will adjust first, then think about the fancy button ��

FredR

You should also check the tension on the kick down cable. The trick is to set this little different from the factory spec if you want "lively" changes.

If I remember correctly the factory spec is to align the kick down cable cup with its seat and then back off the cable one complete turn of the adjuster. I align it and set it 3 turns tighter. This gives you first gear starts when needed. I also run the kick down switch bypass. If you use this you need to adjust the kick down cable so that it will still pull in top gear with very light throttle pressure.

Someone please correct me if I have it the wrong way round- I am tired and it is late night here. Either way I run with the kick down cable approximately 3 to 4 turns tighter than the factory setting.

Rgds

Fred

FredR

Duplicate- no idea why.

dr bob

Hmm. I run mine two turns looser to avoid those fiddly downshifts in L.A. traffic. Now in the high desert with little traffic, I could use some downshifts to help compensate for the altitude. The various adjustment options for the TV cable are the difference between pussycat and cheetah driving impression. With the cable loose, performance is pretty soggy. Snugged to original and one turn tighter adds a tremendous amount of lively. An extra turn or two more as Fred has his must be almost violent.

Besides getting the switch to engage, make sure the pedal actually opens the throttle all the way at the same time. And as much as I like the solid car, the arm that hits that switch seems to bend over time.

safulop

I think it is not quite right to say that it will downshift into the "lowest gear possible without redlining." The 1st gear is very conservative, it will not do a 1st-gear downshift above 25 mph, although 1st is very much taller than that. The lack of a good gear at 25-40 mph has always annoyed me about the 4-speed auto.

FredR

Bob,

I think you would be surprised at just how controllable my setup really is. I struggle to remember the exact position it is in but it is about 3 to 4 turns tighter than stock recommendation.

I "calibrate" my adjustment by tootling along at about 110 kph [approx 70mph] and set it so that I can gently depress the pedal about 1 inch and still pick up some speed without it shifting but any more than that it will drop into 3rd and off we go. This with the kick down switch bypassed as well. With this setup I feel as though my mind changes the gear as it pretty much goes where I want it and when I want it. If I re-engage the kick down switch it is still sort of OK but it feels flat by comparison. Driving a 928 auto with the stock setup is a bit like taking a dump with your pants still in place- you can do it but you really do not want to try it! The only problem I have with this setup is on sharktuning runs- for those I simply disconnect the kickdown cable altogether and change manually.

I also like the vacuum modulator in the tranny set a little towards the firm side for punchy shifts [but nothing too violent]. Of course interpretations as to what is gentle is all relevant. I do not like the stock suspension settings- way too soft for my liking- the Eibach springs I run with are 25% stiffer- I find that "just nice"- others will tell you it is a back breaker [pussies]. It is all relative.

The good old days of open roads with little traffic and no radar have long gone. We now have a lot of nose to tail stuff and that with folks who [to be kind] often do not have the same lane discipline expected in your part of the world.
My 928 copes with this very well indeed- indeed one has to be quite sharp with gaps- leave anything in front of you that you can get a car into and some joker will likely appear before your eyes.

The one issue I cannot resolve is the change between second and first- very difficult/unpredictable even with my setup to get the box to go into first from a rolling start. I found this to be a problem on our autocross events [when we had them] with slow tight/twisty bends- you just never knew if it was going to be bogged down or all hell let loose. I do not have this problem with the box on the Cayenne Turbo S. Just select the tiptronic mode and select what you want- if you over rev it simply changes up regardless.

The MB auto tranny is very robust but it is basically what- 70's technology? Turbomatic 400 type of equivalent? Bullet proof and a great unit for its time but low tech by today's stds.

Regards

Fred

Big Dave

You're probably right. That was just the easiest way to describe how it behaves.

safulop

My mechanic described it as the last and greatest "mechanical" auto transmission. All the good ones in recent times are electronic, I'm told. I'm renting a Chrysler 200 and the shifter is a **** by the radio! Keep trying to find D after backing up and I'm turning up the stereo instead. I hope Porsche never puts a silly thing like that in one of their cars.