W123 200 1978 722.118 shift hard - PeachParts Mercedes-Benz Forum

dmaglione · #1 07-31-2017, 10:20 AM

Dear friend,

I need your help to solve a problems on my mercedes w123 200 petrol 94hp 1978 automatic.

First of all sorry for my bad english...
Since last year I had a problem when shift from neutral to drive....the car shift so hard that looks like car jumps.

Te automatic transmission model is 722.112 and has only the VCV to adjust the shift between gears and anyway has been replaced and set properly.

As far as I understand, to solve the problem I should adjust the "modulator pressure" but this model should not have any regulator.

Does anyone should help me to find a solution? I figure out should be the oil pressure to high. Many thanks in advance to all. Daniele

Frank Reiner · #2 07-31-2017, 10:49 AM

Quote:

Originally Posted by dmaglione

Dear friend,

I need your help to solve a problems on my mercedes w123 200 petrol 94hp 1978 automatic.

First of all sorry for my bad english...
Since last year I had a problem when shift from neutral to drive....the car shift so hard that looks like car jumps.

Te automatic transmission model is 722.118 and has only the VCV to adjust the shift between gears and anyway has been replaced and set properly.

As far as I understand, to solve the problem I should adjust the "modulator pressure" but this model should not have any regulator.

Does anyone should help me to find a solution? I figure out should be the oil pressure to high. Many thanks in advance to all. Daniele

Sorry to say, the 722.118 transmission is for use with diesel engines, and is incorrectly installed with a petrol engine.

A petrol engine, by virtue of being controlled by an air throttle, has reduced atmospheric pressure (vacuum) in the intake manifold. That vacuum is used to control internal hydraulic pressures in the transmission via the vacuum modulator. The vacuum modulator is connected directly to the reduced atmospheric pressure in the intake manifold.

A diesel engine operates with the manifold at full (or greater than) atmospheric pressure, and hence cannot provide vacuum from that source. The use of a vacuum pump combined with a vacuum control valve (VCV) mimics the reduced atmospheric pressure of a petrol engine.

dmaglione · #3 07-31-2017, 11:02 AM

Hi Frank,

first of all many thanks for your quick feed back. Honestly the transmission was native and bought originally with car in semptember 1978.
Probably I made a mistaje and anyway I'm sure that the trasmission has only the VCV valve and no other valves.

In fact I swapped this one because had problems shifting between gears and problem desappeared.

Now, the only problem still going is the torque when you shift from neutral or parking to direct of reverse...VERY HARD.

Ther's any other adjustment to be done?

The transmission os identical to the attached image. Many thanks Frank

dmaglione · #4 07-31-2017, 11:25 AM

Sorry frank, you're right.....it is a 722.112.

Frank Reiner · #5 07-31-2017, 11:46 AM

Quote:

Originally Posted by dmaglione

Hi Frank,

first of all many thanks for your quick feed back. Honestly the transmission was native and bought originally with car in semptember 1978.
Probably I made a mistaje and anyway I'm sure that the trasmission has only the VCV valve and no other valves.

In fact I swapped this one because had problems shifting between gears and problem desappeared.

Now, the only problem still going is the torque when you shift from neutral or parking to direct of reverse...VERY HARD.

Ther's any other adjustment to be done?

The transmission os identical to the attached image. Many thanks Frank

.112 Good! If the installed transmission is the same as the picture, there is no VCV.

The pressure adjustment is a screw inside the modulator (at the right rear of the transmission). It can be seen when the vacuum banjo fitting is removed. Anti-clockwise reduces pressure, and thereby softens the engagement. Note: the adjustment of the control pressure rod controls the timing of the shifts, and the modulator controls the firmness of the shifts.

dmaglione · #6 08-01-2017, 03:42 PM

Dear Frank. Many many thanks for your kindest help. Maybe is my English not very good. ....I understand the vacuum settings for the shift and has been properly set. Every gear goes up or down correctly.
But when you say the modulator where could be set or adjusted? Today I tried tomfind any other screw to trim but nothing found excepting for the screw inside the vcv. Do you have any pictures where show hot to set the firmnes?

Really. Appreciated your help.

Daniele

Frank Reiner · #7 08-01-2017, 06:07 PM

Quote:

Originally Posted by dmaglione

Dear Frank. Many many thanks for your kindest help. Maybe is my English not very good. ....I understand the vacuum settings for the shift and has been properly set. Every gear goes up or down correctly.
But when you say the modulator where could be set or adjusted? Today I tried tomfind any other screw to trim but nothing found excepting for the screw inside the vcv. Do you have any pictures where show hot to set the firmnes?

Really. Appreciated your help.

Daniele

Please look at the picture that you attached in post #3. The circle on the left is labeled "Modulator Valve". That is also called "Vacuum Modulator". Remove the vacuum line from the modulator. Inside the open end is a screw to adjust the pressure in the transmission.

dmaglione · #8 08-02-2017, 12:35 AM

Ok Frank. But this has impact on shift point and not on pressure. In other words when I modify the screw inside I move up or down the point of shift between gears.

My problem is the torque when you goes from neutral to drive or to reverse.

Or probably there are 2 different adjustment on this?

dmaglione · #9 08-02-2017, 01:43 AM

Quote:

Originally Posted by Frank Reiner

Please look at the picture that you attached in post #3. The circle on the left is labeled "Modulator Valve". That is also called "Vacuum Modulator". Remove the vacuum line from the modulator. Inside the open end is a screw to adjust the pressure in the transmission.

Just to be more clear, here a pics of my transmissione with circled in red the VcV, as you know, inside ther's a lever that should be extracted and rotated to adjust the shifting point.

W123 200 1978 722.118 shift hard-722112.jpg

Do you mean ther's inside another regulation point?

Frank Reiner · #10 08-02-2017, 09:11 AM

Quote:

Originally Posted by dmaglione

Just to be more clear, here a pics of my transmissione with circled in red the VcV, as you know, inside ther's a lever that should be extracted and rotated to adjust the shifting point.
Attachment 143494

Do you mean ther's inside another regulation point?

A Vacuum Control Valve (VCV) is used ONLY with Diesel engine vacuum pumps.
Petrol engines DO NOT have a VCV.

What you have circled in red is a Vacuum MODULATOR.

In Post #5 it was explained that the shift points are controlled by the Control Pressure Valve, which is operated by the Control Pressure Lever at the right front of the transmission.
When the transmission hydraulic pressure is changed by adjusting the Vacuum Modulator, there will also be a change in the shift points. However, the shift points can then be corrected by adjusting the Control Pressure. That is done by changing the length of the rod from the throttle to the Control Pressure Lever. This was also explained in Post #5.

dmaglione · #11 08-02-2017, 09:43 AM

Ok Frank,

I'll get this info as gold!! I'll try to change hydraulic presure ad you mentioned and I'll let you know.

One more time many thanks and greetings from Italy.

If you need something from here just let me know!!!

Thanks

Diseasel300 · #12 08-02-2017, 10:30 AM

Do you have access to a vacuum gauge? If so plug it into the vacuum line coming to the modulator and see what kind of vacuum reading you have at idle. You should have relatively high vacuum. If you don't, you likely have a broken vacuum line or a rotten vacuum connector somewhere. Lack of vacuum will cause a very hard shift.

If you have access to a hand vacuum pump, try pulling a vacuum on the modulator. If it fails to hold vacuum, the internal diaphragm has failed.

dmaglione · #13 08-03-2017, 03:10 AM

Wow, great expalation., Yes I'll test it as soon as possible, but I' sure that the modulator is ok because has been replaced entirely with a brand new one.

Probably I have to check the vacuum line for worn or damaged hoses.

Does anyone could sell a vacuum diagram for my car? A long time ago the car was maintened by Mercedes garage but in Italy honestly the service and teh quality is very bad. I'm suposing they reconnected the vacuum hoses wrongly.

If someone ha to sell a vacuum diagram or manual I'll be happy to buy:

Mercedes W123 Petrol - model 123020 Engine type M115938 2.0L 94 HP - Automatic transmission 722.112 year 1978.

dmaglione · #14 08-09-2017, 01:51 AM

Hi. I' ve checked the vacuum value using a vacuum meter and the value at idle is max so it looks like to work perfectly. Now going to check the modulator valve to see if registering it we could reach the firm of shift. Let you know.

dmaglione · #15 08-15-2017, 10:34 AM

Hello guys, after your indications, I've done some tests and below the situation:

First I would like to give you my apologize but I've make a mistake: the tranny is the 722.115 as reported onthe incided numbers on it.

Anyway about vacuum value at idle speed is at maximum on my vacuum meter.
Also I've screwed clokwise and anti clockwise the vacuum modulator valve and it affect a little bit the torque when you go from neutral to direct but the impact is still very high. Can I have another problem for example the torque converter or the primary pump?