shake at gear change? W124 auto tranny
 

My car shakes a little with clunking bang sound at gear change.
Is this normal in W124 cars?

In other auto tranny cars such as Toyota Corolla, Mazda 6, MB M class, I feel no shake or clunk at gear change. Only the engine sound changes from higher tone to lower tone.

I don't think it is... :eek:

Clunking, check your flex discs?

Hard shifting - maybe you need to back the vacuum modulator on the transmission out a bit (soften the shift) or maybe the bowden cable is not adjusted correctly?

They should shift pretty smooth and quick

i've driven a 300D 2.5 Turbo too and I thought it was very smooth shifting...

Thanks.

I had flex joints (124-410-06-15, 202-410-05-47) replaced, because there was clunking noise when I release the gas pedal quickly. This problem was solved.

So it may be due to one of the things you mentioned. I just hope it does not cost much.

The (previous) clunk sound when releasing gas pedal had metallic high tone.

The clunk at gear change is very well damped sound.
3rd to 4th sift is quite smooth but lower gear changes (including R <-> D) make clunk noise and shake.



I thought it could be normal, because I heard long time ago that european auto trannies were more like manual (the gear changes were more noticable to passengers) while Amerian and Japanese auto trannies did less noticable, smoother gear changes.

I had transmission linkage cable adjusted. It feels better, but there is still acceleration surge at gear up shift (but rarely at 3 -> 4 shift), or R <-> D. I have not felt such shaking in other cars - but I do not have much experience with W124's.

Though a mechanic says it should be OK, I will have vaccum modulator inspected in the near future.

Alldata document reads "IMPORTANT. MODULATOR PRESSURES ON 722.4'S & 722.5'S ARE SET AT 50 KPH (31 MPH) AT FULL THROTTLE". I wonder how his can be done unless a shop has large test track.

DRIVE SHAFT CENTER BEARING
 

Dont forget too that there is a driveshaft center bearing mounted in rubber. Mine was totally shot and whenever it shifted up you could feel it bang.

Also, when driving it would wobble and shake the car a bit. You cannot see this bearing because there is an aluminum cover over the driveshaft tunnel. If I rememeber correctly, you have to disconnect the exhaust system to gain access to remove and replace the bearing, fun!

Is there a way to tell which one causes the shake problem?
Shift modulator or drive shaft center bearing?

In my case, the sudden momentary acceleration (and thus shake of the car) comes irregularly.
At putting gear into D or at automatic up-shift, I sometimes feel much shake, sometimes a little shake, sometimes no shake at all.

Have you considered your Transmission mount (ie: Rear engine mount) to be the culprit?

Flex disks and transmission mounts were replaced recently.

I had vacuum modulator adjusted.
It feels better, but I still feel shake at some up shifts.

What is the definition of partial throttle and full throttle?

Full throttle means literally pressing the accelerator pedal to the end?

Then I should rarely feel the shift.

Below is from Alldata.

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Test Drive

During the test drive, it is necessary to check not only the shift points but, particularly, the transitions during a gearshift.

Upshifts at partial throttle should proceed in such a way that they can only be felt by concentrating on them. At full throttle and kickdown, the gear changes should be clearly felt, at the same time, however, the new gear should engage smoothly and the impression of the power of the engine must be retained. For example, if the engine revs up suddenly when the transmission shifts up, this indicates that a servo element is slipping (brake band or clutch) and this must be examined more closely.

Automatic downshifts without throttle are performed at very low speeds and can only be felt by concentrating (increase in engine speed). By contrast, a downshift at kickdown involves not only an increase in engine speed but a perceptible gearshift. At certain speed ranges, it is possible to perform a downshift at partial to full throttle.

Downshifts with the selector lever are either downshifts with the throttle depressed (e.g. on a hill) or braking downshifts without use of the throttle (e.g. on a downhill stretch or for slowing down). Downshifts with the throttle depressed need only a few fractions of a second for the gearshift whereas braking shifts without the use of the throttle require times of 1 to 2 seconds.

During the test, ensure that the transmission is not constantly shifted, particularly under load. During the gearshift, a lot of heat is developed at the servo elements. A reference value in this connection is:

Do not repeat a shift under load more than once within 15 seconds.
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