w124 300e's 722.3 transmission flare, peculiar symptoms

[toilet]

Let me preface this by saying that I am quite happy with the car right now, I'd say about 90% happy. But as perpetual fiddlers, we're always striving for that extra 10%, so would love some thoughts...

RHD 1991 w124 300e 4matic here, m103, 722.3 transmission, odometer broke at 190,000 kms so probably pushing 200,000 kms right now.

Issue:
Transmission flares from 2nd to 3rd only in a specific RPM range AND a specific throttle position. I'd say when I depress the throttle 1/2 way, and the gears want to shift between 1900-2200 rpms, it flares noticeably.
ALL other times, such as with brisk acceleration in higher rpm range, or slow acceleration where it would upshift below 1900 rpm, there is NO flare.

This leads me to believe the problem is vacuum between 1900-2200 rpms.

I have so far adjusted the Vacuum modulator at the transmission one full turn, bowden cable, lubricated all hinges, run some WURTH fuel injector cleaner.

I did all of the above after scouring through all the forum posts on the subject. The flare significantly reduced as a result, but it still exists in the aforementioned RPM range.

Question:

Since shifts are controlled by vacuum, what could possibly cause the engine vacuum to behave in this way? Is there a particular part I should focus on, such as the vacuum modulator? Vacuum pump? etc.

 

[toilet]

Okay, after possibly many months of fiddling, I realized that my throttle cable adjustment screw was broken. So I replaced that. Tough nut to find might I add.
Then, I used the website w124performance (google w124 manuals) to check the factory recommended method of adjusting both throttle cable and bowden.

I set them both up as close to factory as possible. Lubricated linkages again. And voila, the car's flare is pretty much gone completely! Couldn't believe it! Guess the tranny is in decent nick after all!

 

[tjamesbo]

got a flare 2nd to 3rd on my recently rebuilt tranny will have a look at the setting up of that cable / throttle nut mine flares cold and then is fine when hot and only the 2nd to 3rd change flares building up a list of things to check / change i have a separate recent post on it

 

[toilet]

got a flare 2nd to 3rd on my recently rebuilt tranny will have a look at the setting up of that cable / throttle nut mine flares cold and then is fine when hot and only the 2nd to 3rd change flares building up a list of things to check / change i have a separate recent post on it

After several more months of fiddling with the car, here's the strange things I found that effect the shift characteristics on my m103 722.358 transmission (bear in mind the car is no longer 4matic, has been converted to RWD) that no one else mentions:

1. Fuses. When I replaced all original with brand new ones, the flares reduced, and it shifted crisper than before.
2. CO adjustment mixture. I experimented with leaning out the mixture i.e counter clockwise in VERY small increments, around 1/8th of a turn (thinking I was running rich) and it increased flare drastically, no real effect on power. I dialed it back counterclockwise the same amount, and flares reduced to their original setting, power remained the same.
3. EZL trimming plug. For the longest time I didn't know what this was for as I set about testing and replacing other components. Then I finally noticed this, and was super excited about having the ability to change ignition timing on the fly (blows my mind still). It was set to "6". Mine is the EZL-ECE no-kat plug. I switched it to "2" looking for more power, it idled better, but it felt sluggish, no change on tranny flare. Then I shifted it to "S", very slight misfiry roughness observed at idle every 2 seconds, but more power off the line, tranny flare increased. Shifted it to "4", and felt that it gained power off the line, and downshifts more readily, misfire type feeling every 2 seconds at idle, flare increased at part throttle between rev ranges 1900-2200 when cold. Little to no flare when warm. I've stuck with this setting since I use premium gas.

In conclusion, I've developed newfound respect for the deutsche magicians that engineered this car. I've never read anywhere of the above issues having an effect on shift flare (and believe you me I've done some extensive reading), but they're still worth checking out if you've done all else.

 

[ray_hennig]

2. CO adjustment mixture.

Your best bet with that is to measure the duty cycle on pins 2 & 3 on the 9 pin diagnostic socket. It should fluctuate around 50% if all is well. Usually, it is best to use this as a diagnostic measure so if it's not around 50% something's amiss.

RayH