I'm at it again . . . I want a first-gear-start option for my '92 300SE.

We're talking about a 4,000#+ car with 228hp and 229ft-lb torque at a lofty 4100 rpm.

Fortunately, the car does have a (approx) 3.90 gear ratio, but it's still a real slug off the line.

Recently, just playing, I've been occasionally shifting the car to 2 at a stop light, then moving the shifter back to 4 or D before starting off. The difference in performance is notable, even when driving sedately - which is what I do most of the time.

I find that when starting out in 1st, I have to provide far less throttle to get a reasonable rate of acceleration than when I start in 2nd. Additionally, the shift from 2nd to 3rd is far less abrupt as there's less load on the motor and the shift comes sooner. What I mean to say is when I start in 2nd, the shift to 3rd is at a higher RPM and speed for the same acceleration rate vs when I start in 1st. I would be willing to bet that my around-town fuel economy improves with 1st gear start.

When I first got the car, someone suggested 1st gear start was possible by depressing the kickdown switch before starting off. I tried this - no luck. Also tried holding down the switch - no luck.

2 things can allow 1st gear from stop - shift to 2 (when standing still) and back up again (transmission will stay in 1st gear), or rapidly depress the accelerator (don't have to floor it, just shove it about 1/2 way to the floor very quickly). Shifting to 2 is a pain with the gated shifter, and I don't want to be doing that all the time. However, this is far easier on the car because I can accelerate normally.

The downshift to 1st from start is (I'd guess) triggered by the rapid depressing of the accelerator pedal. The EA module detects this and either energizes, or causes another module to energize the downshift solenoid in the tranny.

I've pulled wiring diagrams from AllData, but they're insufficent in detail for me to figure out which wire in the transmission harness goes to the downshift solenoid. I'd like to tap into that wire and see what type of signal gets sent and for how long (instantaneous pulse, or longer duration) when the call comes to downshift to 1st at launch.

If I get that wire and signal identified, I would think I could craft some sort of circuit that uses the VSS output to activate a relay when the car comes to a stop, thereby downshifting to 1st. I would only want the downshift to occur when the car comes nearly to a stop, because the combination of a very short 1st gear (3.59) and the rearend ratio would result in a rather abrupt deceleration downshift.

Any ideas or suggestions?

This is the nonlock up five speed auto, correct?

Did any later (up to '96 models) M104s in the W140 start in first? I'd assume so. If this is true, could you source out some factory info on the valve body to have it start in first OR simply swap the valve body out from a core trans?

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Yes - non-lockup 5 speed. I don't know the answer about other model years - maybe someone will chime in with an answer.