when to shift from 3 to D - PeachParts Mercedes-Benz Forum

JimZ · #1 01-10-2007, 09:45 AM

The first half of my morning commute is on back roads averaging 30-45 mph. This whole time I drive in 3. For the second half I get on the highway and average 50-70 mph, depending on traffic. I guess I should mention that I took the alda out of the car.
What I have been doing is keeping it in 3 when I get on the highway until I get up to about 60 mph for about 30 seconds, then I shift into D. Sort of a mini Italian tuneup every morning.
The question is, is shifting from 3 to D at 60 mph every morning going to lead to tranny problems? Should I shift back to D while stopped before I get onto the highway?
Thanks!

mespe · #2 01-10-2007, 10:10 AM

Why did you remove the alda? your engine no longer uses the boost from teh turbo to increase HP. That's probably why you gotta drive in "3" when going 30-45 MPH.

cgryphon · #3 01-10-2007, 10:15 AM

Non-expert opinion warning!

Manually shifting the auto 240D is a necessity in traffic. My view is that the MB engineers gave you the option of shifting manually, so use it all you want without damage, in a proper transmission.

There are little dots on your speedometer to show you the shift points. I suppose those are the maximum and that’s the way I use them on the 240D. When I "accelerate" with full throttle, the dots are where the transmission shifts on it's own when in auto mode.

Enjoy!

PanzerSD · #4 01-10-2007, 06:15 PM

I guess I have a similar situation, I too, have ALDA removed.
1st gear shifts into 2nd before my needle even begins to move (20 km/h start on my speedo) it puts along 3rd gear kicks in at about 25-to 30 Km/h.
Automatically, the transmission doesn't shift from 3rd to 4th till about 45Km, sometimes longer depending on throttle pressure. I have no functioning Tachometer, so I can't say at what engine speed things happen.

Using Moderate throttle pressure, what speed ranges can I expect my tranny (722.120) to shift at?
and the shifts are HARD and flare from 3-4 occasionally.

When the transmission is COLD it shifts PERFECTLY.. when it gets up to op temp. it seems to get a bit sloppy. I sometimes have to gun the engine to get it fast enough to shift from 3rd to 4th. At 40Kmh, in 3rd is what I'm going to guess to be around 3000+Rpm.

Hit Man X · #5 01-10-2007, 07:36 PM

I shift mine manually all the time.

JimZ · #6 01-11-2007, 09:39 AM

I looked at the little dots on the speedometer. Their relation to where the needle is when my car shifts is way off. The dots are at about... one dot at 30mph, two dots at 45mph, three dots at 75mph. I'm assuming that at the first dot it's supposed to shift into second; at two dots, 45mph, it shifts to third; and at 3 dots, 75mph, it shifts to 4. My car tries to shift into second at about 15mph, not 30mph. I say "tries" because 2nd gear in my car is really just a short flare. So it really goes into 3rd at about 20mph. If I were to leave it in 3 and drive up to 75mph before manually shifting to D, my engine would be screaming.
So, those dots are probably pretty close on a new transmission, but not ours. Has anyone tried starting in 2, getting up to 45mph and then manually shifting to 3? Then take it to 75mph and shift into D? Driving my car in 2 at anything over 15mph sounds like the engine is going to explode.

#7 01-11-2007, 09:44 AM

If your transmission is shifting too fast out of 2nd then you likely have a vacuum leak.

I used to have a sledge-hammer 1-2 shift and a too-soon 2-3 shift. Very frustrating.

I solved several vac leaks in my CD and the trans finally stays in each gear long enough for good power/acceleration. The 1-2 shift is still very firm (esp when the car is cold) but not nearly as whip-sawing as it once was.

#8 01-11-2007, 11:50 AM

Quote:

Originally Posted by JimZ

I looked at the little dots on the speedometer. Their relation to where the needle is when my car shifts is way off. The dots are at about... one dot at 30mph, two dots at 45mph, three dots at 75mph. I'm assuming that at the first dot it's supposed to shift into second; at two dots, 45mph, it shifts to third; and at 3 dots, 75mph, it shifts to 4.

The dot's are the maximum speed where it's safe to downshift without overspeeding the engine.

JimZ · #9 01-11-2007, 12:01 PM

The dots being the maximum makes sense. But my car shifts way below whatever the minimum might be.
Vacuum stuff is one thing I have yet to get into at all. I know I need to buy a mityvac, but from there, I'm lost. Where do you hook it up? How do you determine where the leak is coming from?...I guess before I start leak hunting I'll be doing a lot of searching and reading in the forum.
As far as my car's shifting in general goes, it's really smooth, it just has the
2nd gear flare. Is this something the K1 kit will fix? Or is it definitely a "find the leak first" thing?