Trans sticking in 2nd when cold - PeachParts Mercedes-Benz Forum

irobertson · #1 01-05-2011, 09:41 PM

Hi folks,
I picked up a lovely 1991 300SE a while back.
It runs very well except for one thing, it is hesitant to shift out of 2nd when cold. If I drive away without warming it up fully, it will stick in second for about a minute until it shifts. Once it shifts once, it's fine after that.
Checked the fluid level and it is just slightly below full.

Thoughts on this.... anyone experience similar symptoms?

lou-in-nj · #2 01-05-2011, 10:25 PM

I don't suppose you have the shop manual and I am sure one of the very knowledgeable folks hear will be able to answer your post with expert ease, but for my $0.02 worth regarding theory of operation; Automatic transmissions have clutches and bands that control which gears and gear-rings are engaged and which are held stationary through the various ranges the transmission shifts through. On many tannys the bands are adjustable which means you can reduce the clearance between the band and the gear-ring it attempts to keep from spinning in a certain gear range. Here are some pictures of various bands One side is hydraulically pressed to tighten against the smooth outer side of the gear-ring while the other side usually has a stationary, automatic, or manually adjustable rest-stop. In the case of the former two you must replace the band if is determined that it is slipping, but in the case of the manually adjustable band you usually adjust by backing off a locking nut and screwing in a bolt and then backing off a prescribed amount and then tightening the locking nut. I did this on my Dodge a few weeks ago and the "rear" band required me to drop the pan to gain access to the adjustment while the "front" band adjustment was external. However you must first find a shift or range chart for your transmission. That will tell you which combination of clutches and bands are engaged for each gear and consequently let you determine which if any bands are your problem; Clutches unfortunately are not serviceable as far as I know. Also I have heard some MB trannys start off in second gear range unless you floor the accelerator, so just be careful you are diagnosing the correct gear range. Study the chart and try testing in R,1,2 & D separately; be aware that shifter range 2 may not be the same as second gear in D as was my case. But if it is something else like the shift valve body, you'll need someone else's advice. Good luck! -Lou

lou-in-nj · #3 01-05-2011, 10:41 PM

Sorry, I just noticed you have a late shifting problem and I gave you my slipping diatribe! Well my insight into late shifting is a seized throttle position cable (most times mis-identified/characterized as the "kick-down" linkage) or bent linkage or weak/missing return spring. In transmissions that have this, and I don't know if yours does, the transmission valve body can judge the throttle position and therefore would not up shift if the cable/linkage indicates that the throttle is opened pretty wide, indicating you want to accelerate and not up shift yet. When you back off the throttle the spring either at the throttle body or on the tranny would pull the linkage back and the tranny would then up shift. I've seen gunk build up enough that in combination with an old weakened spring and corroded cable linkage, don't return easily and cause erratic up shifting. But this is all mute if your tranny is electronic or has some other control for up shifting.

irobertson · #4 01-05-2011, 11:16 PM

Thanks Lou,

Car does indeed start off in second gear, unless you depress the accelerator far enough to close the switch under it.
I have also just learned that my car has a programmed shift delay which is intended to help the cat heat up thereby reducing emissions.

Cheers

Ferdman · #5 01-06-2011, 04:09 AM

irobertson, your 1991 300SE is operating properly. Delayed shifts allow the engine to reach operating temperature more quickly and reduce emissions. No need to adjust anything on the transmission.

lee polowczuk · #6 01-06-2011, 08:22 AM

agree with Fred... not sure what year that started.

it doesn't happen with our 89 300ce....but the 95 e320 and the 92 190e with the 2.6 103 work that way.

Cal Learner · #7 01-06-2011, 09:35 AM

Fred, some delay is by design, for the reason you cite, but have you found that a delay of as much as 60 seconds is normal behavior? That seems excessive to me. My 1988 W124 with 722.4 transmission exhibits a short delay when it's stone cold, but for no more than perhaps 10-15 seconds on gentle acceleration. I suppose local climate conditions can play a role, but 60 seconds is a long time to wait for a shift.

Cal Learner · #8 01-06-2011, 09:37 AM

Quote:

Originally Posted by lee polowczuk

agree with Fred... not sure what year that started.

it doesn't happen with our 89 300ce....but the 95 e320 and the 92 190e with the 2.6 103 work that way.

Lee, maybe your CE doesn't do this because everything is better in Palm Beach County?

Sorry I'm not there anymore (for the moment).

lee polowczuk · #9 01-06-2011, 09:42 AM

Quote:

Originally Posted by Cal Learner

Lee, maybe your CE doesn't do this because everything is better in Palm Beach County?

Sorry I'm not there anymore (for the moment).

the e 320 is here as well.

the 190e was here for a short while.

pawoSD · #10 01-06-2011, 12:00 PM

They do that for emissions reasons....it is rather annoying when the temp outside is 15F and it takes 40+ seconds to get out of second. However, it will shift if you exceed 30mph, but then you have to rev to 3200rpm with a cold motor. So its a bad thing either way. I might try to disable it on my 300E.....looks like you can just unplug the solenoid/delay valve on the tranny and that will prevent it.

Hit Man X · #11 01-06-2011, 01:34 PM

My '90 300SEL does it too, normal.

Ferdman · #12 01-06-2011, 02:54 PM

Cal, it may take a full minute for an upshift if the ambient temperature is in the teens and the engine hasn't warmed up much. In bitterly cold weather I normally let the engine idle for a couple of minutes before driving off, so I have not experienced shift delays quite that long. But I don't think longer shift delays are any reason to worry, particularly when the car drives fine after the initial delayed first shift.

Three300Ds · #13 07-08-2014, 11:52 PM

When I called the seller of the '90 300SE that I eventually bought, he wanted me to meet him at his house. He was at his work and was planning to drive straight home to show me the car and let me drive it.

About 5 minutes later, he called back and changed the viewing venue to a place about 5 miles away.

I later figured out that he probably changed the venue when he realized that he would be starting the car cold, with me there to drive it, and risked having to explain when the car was hanging in gear for the first half mile.

To this day, I do not know if he knew it (delays up-shift for emissions) was by design or if he was trying to pull a fast one on me.

Duke2.6 · #14 07-10-2014, 10:41 AM

The theory is that delaying the 2-3 shift when the engine is cold will cause the engine to warm up and go into closed loop operating mode faster. Closed loop operation begins at a coolant temperature of 60C as long as the ECU receives a valid signal from the O2 sensor.

In the EPA emission certification test that lasts about 45 minutes (including about ten minutes shut down for a hot soak) about 80 percent of total emission occur in the first couple of minutes of operation before the the system goes into closed loop mode.

The strategy of delaying the 2-3 shift to warm up the engine faster is probably effective, but very annoying.

Duke