Transmission, Automatic

Getting 1st Gear Starts

>This is in response to the message from Ed Ruiz regarding the linkage
>adjustment required for 1st gear starts always. It seems like there's a
>lot of interest for those of us with automatics that feels sluggish unless
>you're inclined to really step on it (who me?). If we could impose on you
>for a description, it would make the car even more entertaining to drive.
>I've always thought Porsche went overboard in trying to assure smooth
>starts with the second gear start and the asymetrical throttle linkage
>that requires a lot of pedal for a small throttle movement.

Fair enough. Let me start out (pardon the pun) by saying the several methods that I will outline may not work for all AT 928s. Some older 928s have only three forward gears, and they may already start in first. Also these methods may not work if your AT is malfunctioning or in need of service. Asside from the the usual "YMMV" disclaimer, let's begin.

The least intrusive method is DO NOTHING to the transmission. While the car is at rest, place the gear selector in "2". If the AT is working properly, you will be in 1st gear. It will shift to 2nd at about 5,500 rpm, or you can force a shift by moving the shifter to "3" and quickly back to "2". If you leave it in "3" it will shift to 2nd and then 3rd in quick sucession. (As you may know, the 928 AT is exactly the same as a Mercedes Benz AT. I tried the method mentioned in my wife's 300E, and it worked as described.)

The remaining methods will allow 1st gear starts while the shifter is left in "D". The least intrusive still requires a linkage adjustment. There are three cable that are linkages on your 928. MY 86 and older have these linkages connecting to a pivot mounted on the radiator fan bracket. MY 87 and newer have the linkages on the center plenum of the intake manifold. They all have ball and socket connectors with adjustment screws. (The cruise control has no effect on the transmission, so its linkage should not be adjusted.)

Loosen the locknut behing the throttle and transmission linkage balls, then remove them from their respective sockets. (Take care not to damage or lose the pin that locks them in place.)

With the throttle ball off its socket, notice how much it extends beyond the socket. Adjust the length of the linkage so that the ball will fit onto the socket without being pulled or pushed. Reinstall the throttle ball and tighten its locknut. Next, remove some, BUT NOT ALL, of the play in the transmission linkage. Reinstall the ball and lightly tighten its locknut.

Go for a test drive. Leave the shifter in "D" and accelerate slowly to 30 MPH. Count the number of shifts you feel/hear. If it's two, then you are still starting out in 2nd gear. If it's three, you are starting out in 1st.
If you are still starting in 2nd, take note of the length and RPM it takes to shift up to 3rd. It should be holding 2nd longer than it did before you adjusted the linkages. At this point you can either accept it as is, or go back and remove more slack in the linkage. At some point in the linkage adjustment, you will cause the transmission to sense that it is being asked to start in 1st. When you get there you may say EUREKA for all to hear.

Method three requires installation of a parallel kickdown button or switch. I would say more about this, but Leonard Laub has sworn me to secracy. ;^) All I can say is "Join the 928 Owner's Club", you won't be disappointed.

Method four is the most intrusive and costly. It involves revalving the trasmission valve body. I will not provide the procedures for it.

I sure hope this information helps you. As I am writing this from memory, I may have left out a step or two, but the procedures are fairly straight forward and the linkages are easily accessible. YMMV

Let me know how it turns out. Merry motoring, Ed.

p.s.
Please forgive me, but I where I say "ball" I mean "socket" and vis-versa.

Merry motoring, Ed.


Those of you who try this be aware that it may not ever cause your transmission to start in 1st gear, regardless of the amount of adjustments you make. And if you already have a little bit of slipping in your 2/3 shift, it may exacerbate that problem. Not all transmissions respond to this adjustment procedure, so if yours doesn't, don't panic and think something's wrong.

If anybody wants to wire in a parallel kickdown switch, [the procedure is described elsewhere]. But also be aware that the switch, when activated, does not necessarily force the transmission to downshift - rather it permits the transmission to downshift if other conditions exist which are 'requesting' a downshift.

In my case, the transmission downshifts with much less throttle input if the switch is closed (i.e., more easily obtained 'part-throttle' downshifts). So it makes the tranny much more responsive. But it does not downshift the moment the switch is closed if you are motoring on down the road in steady-state (say 30 mph). You still have to hit the throttle, just not nearly as much as before.

Steve -87S4/auto/GPW