Hard shifting between 1st and 2nd
 

Hi

I'm a new Mercedes owner (1993 400E automatic) and have a question. When I took the car out for a test drive before I bought the car, I noticed that the transmission shifted fairly hard between first and second but nice and smooth between the other gears. (The car slips into drive or reverse smoothly.) I had never driven a Mercedes before and I was so concerned about it that I put a condition on the sale stating that I would have the car checked at a Mercedes dealer. I took the car to a local Mercedes shop and let the shop foreman take the car for a drive. He assured me that the hard shift was normal between first and second and that only on the newer Mercedes is the hard shift eliminated because of newer technology. I accepted the shop foreman's explaination and bought the car.
Do you find that your Mercedes has the same condition?
I guess I'm looking for some reassurance from another source besides the shop foreman.

have the control module on the side of the trans changed, if it is vacuum controlled make sure vacuum is coming while car is running before changing it

To my knowledge, the mechanics of the 1-2 shift are different than the 2-3, & 3-4 shift.
Also, when the car is cold, the 1-2 shift, and 2-3 shift will be much harsher.

I have the same hard shifts from first to second in my 1992 300TE 4matic when it's cold. All other shifts up and down are smooth too. I also bought my car used, and both the previous owner & dealer told me it was "normal". When I can, I try to drive it as far as I can in first gear to warm it up a bit and have found a 1/4 mile is often far enough to get a smoother upshift.

The harsher 1-2 shift is a well known, and oft described, Mercedes Benz "feature".

On the 722.4 transmission, there is a "cold-shift relay." Mercedes engineers were very clever; to warm up the catalytic converter faster, in order to drastically reduce emissions, the transmission holds 2nd gear until either the coolant temperature has reached 50d or the engine is revved above 3100 RPM.

There you have it in a nutshell!

If it has over 100k on it, you might reseal the front servo and add .25mm of shim to the apply piston. There is a measuring device for this but, the thing wont fit in the servo opening with the unit in the car.



These servos leak and the band wears creating more clearance which creates harsher 1-2 shifts. There also is a for worn bores in the case that involves chambering a 30 deg angle behind the seal (not the pin side, it'll blow the seal off) to allow fluid pressure to enhance sealing ability.



Whoever suggested checking the modulater was dead on as well, however that will rarely affect a single shift. Modulator and bowden cable adjustments are critical to proper shifting.


Joe

As Joe stated a combination of control pressure cable adjustment and modualtor adjustments can often schmoose things over.

That which can't be adjusted can also be changed through valve body modifications.

Hard changing gearbox
 

Now I know why the sales rep at some dealers gave the excuse that the tank was empty and had to go and fill it up at the next service station. They took the cars for a 5km ride so the 1st to 2nd gears shifted smoothly before they gave me the car to test drive!!! How crafty they are!!! One didn't allow me to get up to 100kph so I won't find out it won't be comfortable at that speed without a cruise control due to the heavy pedal!!! Mine is a 1994 used C180 Euro version which also has this harsh 1st to 2nd gear change in the mornings whatever the outside temp is. The car drags for a long time on 1st(or is it 2nd???) especially uphill(my area is hilly) and is very annoying when it is making such a noisy roar and crackle at 2000rpm and when it changes, boy does it give you a jerk from behind!!! Very un-Mercedes you'd say! Feels like a car from a company making cars for the first time!! Even Hyundais, Nissans, Kia and Daihatsus don't have this kick in the butt feature? Mercedes please read this posting!!!

read....
 

read klasse's second entry and leave this one alonewhether YOU like it or not it was intended

Harsh changes from !st to 2nd or is it 2nd to 3rd?
 

Referring to what David C Klasse mentioned about the cold shift relay and what is happenning to the auto gear box when its still cold, I personally don't wish to upset anyone by my comments, but don't you think that this excuse that it was designed to work this way to heat up the catalytic converter quickly to reduce emissions is really a sly excuse for BAD engineering design and trying to get away from this by giving a "good" reason for having it? Tell me why no other car manufacturer has this wonderful kick form the back feature if its so good for the car? Why has it got to be from Mercedes? As far as I am concerned, if any other manufacturer was involved, this "feature" would have been considered a design flaw and a new tranny designed before the car went out of the door!!!

You're right Hocky, it's all spin. It's no different than the cars with "child safety windows" for the back seat doors. They're not made that way for kid safety, it's a design flaw; the window can't go all the way down because of an intruding rear wheel well. But instead of admitting that, they spin it as a child safety feature and people accept it. However, even with this "design flaw" in my 300TE 4 Matic, I still really enjoy the car.

Hocky,
No, this is a DESIGNED & very intended method of warming the catalytic converter.
Don't nkow why you let it bother you so much!? It's no big deal really.

My car sits outside, and when I start it, I let it run for about 5 minutes or so before driving. When I do this, the shifts are normal. Try to take it easy for an additional 5 minutes or so, and then the harsh shifts will go away.

I get these too if I don't let the car warm up for a few minutes. Even in the summer, this happens. A 5-minute warm-up makes a HUGE difference.

Hope this helps.

Take care,

Michael.

Kick in the back tranny
 

David, I cannot understand why you are so protective of the brand? We all know that this tranny has a problem and so does a lot of other car manufacturers all over the world who have made auto gearboxes in cars with catalytic converters which do not have this problem of having to warm it up first for the 5 minutes or so to give you a smooth gear change otherwise please wear a neck brace! As a matter of fact this happenned to my BMW 320 a while back an 80's model also automatic and I thought it was crazy. When I took passengers, I had to tell them in advance about this rude shock they will be suffering! Anyway guys this is a PUBLIC FORUM and we are entitled to have our say as long as we keep it gentlemanly.