BauerR

Been combing through old threads and can't really find exactly what i'm looking for.
1) From a stop, will I start in 1st or 2nd gear? If not first, how do I do so?

2) If I were going to take the car down the 1/4 drag strip, whats the best method for the quickest shifts? Put it in D and mash the gas or row through the gears?

3)What aftermarket options, if any, are available for faster and harder shifts?

4) A Kuhn Twin Turbo kit is in my future, what kind of power are these automatics able to hold?

Thanks,
Rich

ammonman

You will move off in 2nd unless you give it a quick stab of throttle which will make it drop into 1st at launch. alternatively you can move the selector into "2" while stopped, then move it back to "D" after the trans selects 1st gear. You will need to apply a fair amount of throttle to keep it in 1st. These Mercedes sourced automatics shift based on road speed and throttle position, not vacuum like an American automatic of the same vintage. As far as quick shifts go for straight-line speed, put the pedal to the floor and let the trans do it's thing. From a stop it will select first gear moving off and hold each gear to the red line before up-shift. Making the shifts firmer is as simple as adjusting the modulating pressure. Look at the WSM for how. There are some alternate springs for the valve body available. Search is your friend here. As far as power goes these auto's are very tough. The original Mercedes trans these are based on was used for high HP and heavy torque applications.

Mike

BauerR

Thanks for the help!

G8RB8

http://redirect.viglink.com/?format=...d-answers.html

davek9

If I were to drag race an Auto 928, (and I say "if" LOL, this is the way I'd go about it.

Place shifter in #2, hold brake, nail the throttle release brake, keep peddle to the floor (engaging the Kick Down switch), the Trans will Auto upshift to 2nd on its own on or about Redline.

Keep peddle to the floor until desired Redline is reached in 2nd, then bump the Shifter to #3.
Keep peddle to the floor that should take you to somewhere about 120 MPH.

I doubt you would ever need "D" on a 1/4 mi drag strip with a "stock" setup.

Also if adding Turbo or any Power adders, you will want a LSD diff, else what's the use as you won't put the power to the pavement, right?

The Autos seem to be good for over 600 HP from what I've see, if its in good working order.

Let us know how you do
Dave K

James Bailey

Perhaps some of the "durability" of the later automatic comes from the transmission protection switch which retards the ignition timing (to reduce power) on two of the upshifts....which means someone somewhere (Porsche or Mercedes) felt that the transmission NEEDED protecting at stock power levels. But yes they do seem to hold up pretty well to street driven levels of abuse......

Speedtoys

"transmission protection switch"

This is a switch? I thought it was more of a brain/code issue?

Lizard928

You can modify the valve body to start in 1st gear every time.

James Bailey

It talks to the ignition brain....tells it to retard the ignition timing...trust me it is there but it never said on which shifts it was used . Buried away deep in some tech paper that I was reading many years ago

Speedtoys

Ya...just not many wires leading from the trans itself, so was wondering what I missed between the various other functions, like reverse, start safety switch, etc.

Rob Edwards

Good discussion of the transmission protection switch leading to the EZK, here:

https://rennlist.com/forums/928-foru...on-switch.html

And at Theo's site:

http://jenniskens.livedsl.nl/Technic...4/MyTip478.htm

Speedtoys

Ok...I need to debug this.

If the switch or wiring has an issue and this stays open, might explain why some days I have harder shifts 'at throttle' than others...it seems.

Vilhuer

IIRR late automatics will change up from 1st to 2nd on lower rpm than higher gears to protect transmission. Properly working A28/16 should change to 2nd at around 5k rather than redline.