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  #31  
Old 12-10-2009, 11:42 AM
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Quote:
Originally Posted by 4x4_Welder View Post
The programming of the valve body is to start in second under normal driving conditions, if you stomp on it then it kicks down to first and you get all four gears.
According to the MB manual, only slight pressure on the narrow pedal should cause a downshift to first. Certainly, "normal driving conditions" would involve more than slight pressure.
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  #32  
Old 12-10-2009, 11:53 AM
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Quote:
Originally Posted by tangofox007 View Post
According to the MB manual, only slight pressure on the narrow pedal should cause a downshift to first. Certainly, "normal driving conditions" would involve more than slight pressure.
Is is possible that this downshift is not noticeable with very slight pedal?
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  #33  
Old 12-10-2009, 11:56 AM
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Originally Posted by Brian Carlton View Post
Don't believe everything that you read.
My '82 300D shifts precisely as the manual describes. With no throttle pressure, it moves off in 2nd. Step on the pedal, it downshifts. Absolutely no doubt about it.

Furthermore, my transmission only downshifts to 1st when slowing to a stop if the selector is in L; that downshift is incredibly noticeable.

Quote:
Originally Posted by Brian Carlton View Post
Don't believe everything that you read.

I think we should do a poll on it. It might be specific to a given year. Certain people swear by the second gear start...........others, including myself, have never had it occur. This cannot be a simple quirk.
The 2-1 downshift is very subtle and could easily be missed by the average operator. Furthermore, a maladjusted Bowden cable could easily prevent proper operation. (A cable that is too tight would communicate throttle pressure that does not actually exist.)
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  #34  
Old 12-10-2009, 12:01 PM
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Quote:
Originally Posted by tangofox007 View Post

The 2-1 downshift is very subtle and could easily be missed by the average operator. Furthermore, a maladjusted Bowden cable could easily prevent proper operation. (A cable that is too tight would communicate throttle pressure that does not actually exist.)
I'm with you on the tighter than spec Bowden cable. The SD is slightly tight to delay the shifts a bit because it doesn't need much pedal to move out smartly. If the cable is not at spec, the transmission might be using first gear as standard.

If it was a bit warmer, I'd experiment with it............
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  #35  
Old 12-10-2009, 12:25 PM
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The ATSG manual very clearly indicates that only some V-8's get the second-gear start. All diesels (of 722.3 vintage) rest in second, then immediately shift to first upon application of the skinny pedal. This shift is not easily felt. Both my 123.133 and 126.125 operate in this prescribed fashion.

As mentioned, the 3-4 shift is pretty slight under "normal" driving. To test it, use "your normal" skinny pedal to run the car up to about 40 MPH with the shifter in "D." While maintaining 40, shift to "3." RPMs and noise will slightly increase, and you'll hear/feel the shift. Shift back to "D." RPMs will drop a little, and you'll hear/feel the shift.

Another way to test is "backwards" shifting. Drive the car at 40 in "D" and shift to "3." Do you get a downshift? Then you were in fourth. Drive the car at 25 in "3" and shift to "2." Did you get a downshift? Then you were in third. Continue at 25 in "2" and note RPM (or engine sound if tach kaput or not fitted). Leave lever in "2" and come to a stop. Speed back up to 25 while noting engine performance. If it won't go back to 25 without sounding like the engine might come free from its moorings, you are locked in first. When you then shift to "3" you may feel two very quick shifts (1-2 then 2-3).

The shift behavior of a four-speed with only three selections is a bit perplexing. "D" gives four gears of operation. "3" gives three gears of operation. "2" DOES NOT GIVE TWO GEARS OF OPERATION. Rather it will hold it in first upon acceleration, or upon decel will shift to second if you're going less than about 20, or will shift to first if you are going less than about 30 (look for the two dots on the outer edge of the speedo rim) and floor it.

The dots are for full-pedal upshifts or safe operating speed. One dot for 1-2 shift. Two dots for 2-3 shift. Three dots for 3-4 shift.
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  #36  
Old 12-10-2009, 12:30 PM
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Originally Posted by BoiseBenz View Post
. "2" DOES NOT GIVE TWO GEARS OF OPERATION. Rather it will hold it in first upon acceleration, or upon decel will shift to second if you're going less than about 20, or will shift to first if you are going less than about 30 (look for the two dots on the outer edge of the speedo rim) and floor it.
From a standstill "2" will hold the vehicle in first gear. However, if you shift to "3", the transmission will shift to second. If you then shift back to "2", it will hold the vehicle in second and will not drop back to first unless you slow the vehicle to about 10 mph. It will return to first earlier than it's normal behavior when in "D".
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  #37  
Old 12-10-2009, 01:14 PM
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Originally Posted by Brian Carlton View Post
From a standstill "2" will hold the vehicle in first gear. However, if you shift to "3", the transmission will shift to second. If you then shift back to "2", it will hold the vehicle in second and will not drop back to first unless you slow the vehicle to about 10 mph. It will return to first earlier than it's normal behavior when in "D".
This thread just got very interesting. The thoughts and advice here are great. I'm going to keep fiddling with the Bowden cable until I emulate the responses here.

My most recent findings are that only under heavy full-throttle acceleration I can get into 1. Normal pedal pressure has it starting in 2 and upshifting as normal.

Now that I'm confident that the transmission is operating close to normal I have a question on clunking. It clunks upon shifting into gears up or down. I'm under the assumption this is a mount or bushing issue. I reused the original transmission mount, which looked to be fairly clean and firm, but I didn't pay much attention to it.
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  #38  
Old 12-10-2009, 03:30 PM
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Originally Posted by tr1cky View Post
Now that I'm confident that the transmission is operating close to normal I have a question on clunking. It clunks upon shifting into gears up or down. I'm under the assumption this is a mount or bushing issue.
While it could be an issue in the diff, the most likely cause of clunking is insufficient.........or non-existent...........vacuum to the modulator.

You'll need a vacuum gauge and you'll need to T it into the modulator line (the line to the transmission) and put the gauge in the cabin so that you can watch the gauge while you drive it. My suspicion is that your gauge will read zero or very close to zero under all conditions.
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  #39  
Old 12-10-2009, 04:13 PM
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Originally Posted by Brian Carlton View Post
While it could be an issue in the diff, the most likely cause of clunking is insufficient.........or non-existent...........vacuum to the modulator.

You'll need a vacuum gauge and you'll need to T it into the modulator line (the line to the transmission) and put the gauge in the cabin so that you can watch the gauge while you drive it. My suspicion is that your gauge will read zero or very close to zero under all conditions.
Prior to the transmission swap I went through various vacuum diagnostics and at that time showed that there was adequate vacuum at the modulator. The original modulator in the old transmission was not holding vacuum and the pin behind it was broken.

I will check vacuum at the modulator again to be safe.

Thanks for the thoughts here.
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  #40  
Old 12-14-2009, 03:02 PM
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All Dialed In

Thanks to all for help and suggestions.

After continuous tweaking and nearly giving up I have the bowden and vacuum adjustments where they need to be. It is hitting shift points up and down as it should under normal and full acceleration.

It does shift to 1 on a hard accelleration, otherwise starts in 2.

2-3-4 normal acceleration
2-1-2-3-4 hard acceleration

Will do K-1 spring next.
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  #41  
Old 12-14-2009, 07:56 PM
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Quote:
Originally Posted by tr1cky View Post
Thanks to all for help and suggestions.

After continuous tweaking and nearly giving up I have the bowden and vacuum adjustments where they need to be. It is hitting shift points up and down as it should under normal and full acceleration.

It does shift to 1 on a hard accelleration, otherwise starts in 2.

2-3-4 normal acceleration
2-1-2-3-4 hard acceleration
That sounds like the downshift to 1st only occurs when the kickdown switch is actuated. It should occur with anything more than slight pressure on the accelerator pedal. I suspect that you are a bit short of being "dialed in" at this point.
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  #42  
Old 12-14-2009, 08:23 PM
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I don't know if it is possible, but your transmission acts exactly like the one in my 500SEL. It starts in 2 nd unless you push hard on the go peddle. Is it possible the transmission you put in came from a V8 gas car?
Paul
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  #43  
Old 12-28-2009, 02:35 PM
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Quote:
Originally Posted by tangofox007 View Post
That sounds like the downshift to 1st only occurs when the kickdown switch is actuated. It should occur with anything more than slight pressure on the accelerator pedal. I suspect that you are a bit short of being "dialed in" at this point.
I'll give you that, and I'll check further. I had a chance to drive a family member's 300SD of the same vintage and I concur that the 2-1 downshift at start was somewhat seamless.
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  #44  
Old 01-07-2010, 04:16 PM
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I'm still finding that only a good hard push of the pedal to the floor gives me a downshift to 1 from a standstill. It seems as though my other shift points are on point. Under full acceleration It shifts in unison with the dots on the speedo.
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