W124 rough transmission shifting

[sub_zero]

Hi all,
I have my W124 for 7 years now,really happy miles (apart from changing the wiring harness ),I got used to every thing in it.
Few days ago I went with a friend to see another W124 for sale,I drove it and I discovered that the transmission shifting is very very smooth(you cannot notice the shift),my W124 is not the same,it has rough shifting compared to it.
My car shifts in time and and I change oil and filter on regular basis.
My question is,what could make the shifting rough? is it an easy problem or a major problem?
Thanks for all.

 

[kth286]

could be the vacuum system not fully sealed.

the change should be so smooth you do not know which gear you are in.

 

[mattc]

could be the vacuum system not fully sealed.

the change should be so smooth you do not know which gear you are in.

Does anyone have a diagram of all the pipe work associated with the vacuum system they could post?

 

[grober]

Gear shifts are modulated by the control cable which is linked to the throttle linkage and the inlet manifold vacuum via a vacuum unit bolted to the side of the gearbox. Together they modify the gearbox control pressure which affects the smoothness of the changes. Check the control cable adjustment and that there are no vacuum leaks.[common fault due to perished rubber connectors or damaged vacuum lines]

 

[grober]

Does anyone have a diagram of all the pipe work associated with the vacuum system they could post?

this applies to the North American 722 series gearboxes 4 AND 5 SPEED.

 

[sub_zero]

I recall there was vacuum leak in the headlight level adjustment( 1 year ago),I bought 3 meters of tube and rubber connectors from the local dealer and installed them myself,I did so because the level adjuster wasn't working,it is now working but slow .
Last month I changed the kick down cable,it was broken,I saw the vacuum tube , the rubber connectors and the vacuum unit(which was also provided with the new cable),but not sure whether they need replacement,the car now shifts up and down as before .
But one thing for sure the transmission wasn't shifting smoothly since I bought the car.
Thanks Grober for the rich and wonderful information,how would I check the control cable adjustment?

 

[grober]

Here's a thread detailing the cable adjustment. post #10 C200 (W202) Automatic Transmission Problem - Benzworld.org - Mercedes-Benz Discussion Forum

and this one which deals with the vacuum modulator on the 190 =same type of gearbox. DIY W201 Transmission Modulator Removal, Replace, Trobleshooting & Common Problems - Benzworld.org - Mercedes-Benz Discussion Forum
I would put these links in your favorites since they are pure gold!!!

 

[Tonison]

Thanks Grober for your wealth of knowledge of MB's.

 

[Celicasaur]

Thought I'd bump and old thread to keep the knowledge in one area.

My transmission (E320 M104 motor) has harsh upshifts mostly from 1-2 and 2-3 (still apparent in 3-4 and 4-5 but just not as bad) and I'm wondering if something inside the transmission is slipping or if it's related to this vacuum thing.

For what it's worth, when the gear shift takes place, I can hear the engine rpms momentarily rise and then drop back down once the next gear comes into play, which makes me think the tranny itself needs a rebuild.

Any thoughts, based on my description?

 

[altreed]

I would suggest changing the oil in the gearbox. As a maintenance schedule I now replace the ATF every 60k whatever the car is. Prevention is better than cure.

 

[WDB124066]

Thought I'd bump and old thread to keep the knowledge in one area.

My transmission (E320 M104 motor) has harsh upshifts mostly from 1-2 and 2-3 (still apparent in 3-4 and 4-5 but just not as bad) and I'm wondering if something inside the transmission is slipping or if it's related to this vacuum thing.

For what it's worth, when the gear shift takes place, I can hear the engine rpms momentarily rise and then drop back down once the next gear comes into play, which makes me think the tranny itself needs a rebuild.

Any thoughts, based on my description?

That's exactly how they are supposed to work, BUT it is normally the 3-4 and 4-5 shifts that are firmer than 2-3. You will hardly use 1-2 normally. I suspect somebody has put a spring kit in your trans to firm the normally 2-3 sloppy shift. It makes it slightly firmer than the other shifts which you appear to suffer from...?

You can locate the modulating pressure adjuster on the left side of the trans and rotate it anticlockwise to soften the shift or clockwise to firm the shift.This adjustment will operate on all shifts. You can pull out the plastic adjuster and reinsert it after rotating it to get more of a stroke for adjustment. The O ring stops the dust going in not the oil from coming out so no sweat if you have a little fight getting it to re-seat properly. However be careful of the tiny metal square drive piece that should be in the back of the plastic adjuster but may find it's way to the floor- start with a very clean floor.
In the picture the adjuster is the white circular plastic thing that sits on top of the black circle immediately aft of the forward two pin electric connection.

 

[Celicasaur]

I would suggest changing the oil in the gearbox. As a maintenance schedule I now replace the ATF every 60k whatever the car is. Prevention is better than cure.

That's a good idea. I'm not sure when it was changed last, so yeah I will start shopping around for a filter and the fluids to do over the xmas holidays

That's exactly how they are supposed to work, BUT it is normally the 3-4 and 4-5 shifts that are firmer than 2-3. You will hardly use 1-2 normally. I suspect somebody has put a spring kit in your trans to firm the normally 2-3 sloppy shift. It makes it slightly firmer than the other shifts which you appear to suffer from...?

You can locate the modulating pressure adjuster on the left side of the trans and rotate it anticlockwise to soften the shift or clockwise to firm the shift.This adjustment will operate on all shifts. You can pull out the plastic adjuster and reinsert it after rotating it to get more of a stroke for adjustment. The O ring stops the dust going in not the oil from coming out so no sweat if you have a little fight getting it to re-seat properly. However be careful of the tiny metal square drive piece that should be in the back of the plastic adjuster but may find it's way to the floor- start with a very clean floor.
In the picture the adjuster is the white circular plastic thing that sits on top of the black circle immediately aft of the forward two pin electric connection.

Thank you....how interesting. I wonder why anybody would want to make the shift firmer in such an unsporty/dull car I like my W124 smooth and silky...it's the cars party piece! :bannana:

So you think it's 'normal' (granted with adjustment needed) that it throws into gear on upshifts and I can hear the rpms momentarily suddenly rise? I wonder if this has been done by the previous owner to mask a failing transmission....nevertheless if it's not too cold this weekend, i'll have a play with the adjustment thing and report back

 

[WDB124066]

Spring kits can be fitted to reduce the flare on 2-3 up shift, they are effective and make the shift firmer with no adjustment of the lever mentioned before. BUT you are now out of sync with the rest of the shifts in that they are not firmer - BUT then again they were not flaring as much as 2-3 in the first place. Spring kits are a compromise and something that is done to just delay the inevitable. To put a kit in for 3-4 you need to disassemble the trans substantially, at which point in time a rebuild is more beneficial.

Yes, rising just before engagement on upshift is normal, especially in a worn [clutch pack clearances] trans.

Are you slow into reverse?

When mine reached the point yours appears to be at at 225 000 kms I bought a rebuilt one from Daimler's Classics Center in Fellbach via The Classics Center in Irvine. It was the cheapest way to get a properly rebuilt trans. 25 000 kms in and I have no complaints at all - they are suburb units, as they should be.

 

[Celicasaur]

I wasn't able to fettle with the car over the weekend due to rain...boo!!

Slow into reverse....I'd say no more slower than any other Mercedes I have driven tbh. They're all pretty slow going into reverse, but I wouldn't say this one is especially any slower.

However I do think it might be a good idea to get a quote on a rebuild from a local auto tranny specialist. You're right, it's just delaying the inevitable. I think the tranny will carry on driving the car for many many miles to come, but I just find it irritating and it detracts from the driving experience when it suddenly surges in rpm before the next gear catches on, or how it throws itself into the next gear up.