FINALLY had a new transmission installed.....on test drive, mechanic informed me that the 2B lockout (gear shift pulled all the way down and pressed to the right) was not working. He said possibly a neutral safety switch or electronic sensor might be the cause. should I replace the neutral safety switch or electronic sensor or both?

just updated my profile with the makes and models of cars, this question refers to a 1991 560SEL transmission issue.

test drove the car last evening (1991 560SEL)...took it on the highway for some cruising tests. car seemed to shift and drive fine through all gears. only issue is that when the car is first started in the morning, it takes about three seconds to engage into drive (D). after the initial engagement into drive, the transmission takes only about two seconds to engage into drive. any thoughts on this? also, when I picked the car up after the transmission rebuild last Wednesday, the owner of the shop showed me how to initiate first gear start (step on the brake and blip the throttle simultaneously). question: does the transmission automatically revert to second gear start at the next stop light?

ALSO, when the shifter is pulled ALL the way down into 2(B) position, he mentioned that the transmission was not responding properly (something about using the transmission as a brake when coming down a mountain??). He said that possibly a sensor or neutral safety lock out switch might be responsible. any thoughts on that?

The selector has two distinct positions at full travel. Pull it all the way back and you get 2 - meaning it will hold the transmission in 2nd gear when accelerating. This can also be used to control speed during long down-hill runs - but you'd need a pretty steep hill to require it.

Most automatic transmissions have downshift interlocks that prevent too low a gear from being selected at too high a speed. For instance, selecting 2 at 65mph will probably just get you 3rd. As you slow down below the maximum rated speed for 2, the transmission would then downshift to 2nd.

B is the second spot selected at 2 by moving the selector to the right. Choosing 4, 3 or 2 is a mechanical connection to the transmission. B is not mechanical, the connection is electrical. There's a small contact switch in the shifter housing that is pressed (don't know whether the circuit is opened or closed when the switch is pressed) when you move the shifter lever to the right. This selects 1st gear. 1st gear in MB autos (most that I am familiar with) is a very short gear (high numeric ratio), so you probably would never need it to control downhill speeds. There are times when you need it starting out - best example is trying to put your car up on ramps for service, or if you tow a boat, pulling it out of the lake.

If you can get 1st by the brake/throttle trick, but not by selecting B, then I'd first check the connection to the switch in the shifter. You'll have to pull the console up around the shifter, which I have no idea about on your chassis. There have been people who've re-purposed the child-safety interlock switch for the windows as a FGS (first-gear-start) switch. One position of the switch gets normal sedate 2nd gear starts. The other position gets "hold on to your hat, Mabel - here we gooooo".

The difference between the brake/throttle selection of 1st and the shifter selection of 1st is where the shifter is positioned. Brake/throttle triggers 1st even when the shifter is in 4. 1st gear starts, then the transmission upshifts normally through the gears. Using B to get first occurs with the shifter (mechanically) positioned at 2 - no upshifts occur (although I bet it will shift to 2nd and hold there).

The transmission is designed to start in 2nd gear all the time, unless you select B on the shifter, or rapidly open the throttle at takeoff. My 92 300SE will kick back to first if I just really mash the pedal - I don't have to trip the kickdown switch under the pedal - your results may vary.

To answer your question, when you blip the throttle while on the brake and the car shifts to 1st, it will still start out in 2nd when you come to the next stop.

As for the delay in shifting to D - I wouldn't think more than a second or so would be typical. If yours is taking longer, there's something amiss.

Hope this helps.

On the Porsche 928 S4 which uses the same 4 speed automatic transmission as this car, you can wire a parallel switch to the kickdown switch on the throttle to get first gear when starting.

special thanks to wbrian63 for the detailed explanation which makes it easier to understand how this transmission functions. What a car!