Just so you all know, I did search forums and DIY by parts… sections.

Background: 1992 400E 4speed auto with 214,000m Transmission fluid/filter changed at 175,000mile (and expect to be doing another one very soon).

One note here: when I did that fluid change, did drain the torque converter, but was provided Dextron III as an equivalent to the MB Trans Fluid. Today at NAPA they searched and didn’t find any cross reference for the 1992 model year 400E (1995-? Did have Dex III as cross reference).

Fluid level Okay, color looks alright / no burnt odor. This car does a lot of around-town driving, so lots of shifts at low speed with very moderate acceleration.

The Issue: as it warms up it actually shifts a bit harder 1-2, 2-3. The first coldest shift of the day 1-2 can be quite normal. It now feels as though it’s really slamming into gear once warmed up a bit.

This isn’t every time, but has become almost all of the time. Occasionally I’ll remark to myself “wow, that was a smooth one”. The next shift can be hard however.

Additionally the 3-4 shift seems uncertain. No flaring occurring, it just feels as though there’s a slight “shudder”, especially when the engine rises just above 80 degrees on the temp gauge.
When a bit more aggressive on the pedal, the shifts actually seem to feel more normal. Too much of this however and I might find a trailer hitch of a Ford F-250 buried in my radiator.

Can’t associate the onset of this with anything above, or even if it’s new, but when shifting down to 2nd when driving down steep hills, and coming to a stop, the car does a hard shift into 1st gear. Is this normal? It’s described elsewhere as a downshift clunk, and this is the only occasion when I experience that.

In the past adjusted shift modulator counter clockwise to soften shifts, and recently adjusted that 4 notches back. That didn’t seem to have any notable effect. Have I reached the end of adjustment, or will it just not move futher when I hit that point?

I’ve read posts and encountered as potential culprits: fluid level (okay); shift module adjustment (tried per above); Shift module itself; Vacuum (tube); engine speed sensor.


With this host of symptoms to offer, any ideas Benz lovers?

You need to see of the modulator is holding vacuum. I'm guessing that it may have started leaking causing the erratic shift quality. I'd check that before digging any deeper.

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90 300TE 4-M
Turbo 103, T3/T04E 50 trim
T04B cover .60 AR
Stage 3 turbine .63 AR
A2W I/C, 40 LB/HR
MS2E, 60-2 Direct Coil Control
3" Exh, AEM W/B O2
Underdrive Alt. and P/S Pulleys,
Vented Rear Discs, .034 Booster.
3.07 diffs 1st Gear Start

90 300CE 104.980
Milled & ported head, 10.3:1 compression
197° intake cam w/20° advancer
Tuned CIS ECU
4° ignition advance
PCS TCM2000, built 722.6
600W networked suction fan
Sportline sway bars
V8 rear subframe, Quaife ATB 3.06 diff

Wondering what I'm looking for in terms of where the vacuum to the modulator originates from. As this car is nearly 20 years old, I thought I'd check that too.

Just follow the vacuum line from the modulator.

1992-1995 400E:
http://w124-zone.com/downloads/MB%20CD/W124/Index/119index.html

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1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible

A leaking modulator in my case . For a good measure replaced fluid (Dexron 3)and filter .
smooth shifts now.
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