Jerking backlash behavior in 190D with manual transmission >>> VIDEO <<<
 

Remember your first driving lesson? You put your foot on the gas without resting your heel on the floor. You pressed down, which made the car move forward away from your foot, which made the car slow down, which made your foot press harder on the gas, which made the car accelerate again. Back and forth, chugging down the road.

The Behavior:
The above description is an exaggerated version of what my 190D does, mostly in 2nd and 3rd gears. I can minimize this effect through careful driving. It mostly happens when the engine is producing very little power, or slight braking, such as when I approach an intersection and start reducing power, or when I reach the top of a hill and reduce power for the decent. I see the same behavior when the cruise control is on; if anything it is worse with the cruise control.

The Car:
The car is a 1985 190D 2.2 (originally an automatic) into which I have recently installed the transmission from a 1987 190D 2.5. It still has the original rear flex disk, but I installed the front flex disk that came with the transmission. I also installed new motor and transmission mounts; the ones specified for a manual transmission.

Evidence:
I have found there is quite a bit of backlash in the drive train. I did this by jacking up one of the drive wheels, and measuring the amount of movement at the circumference of the tire in various gears:
1st 1"
2nd 1.5"
3rd 2.0"
4th 2.5"
5th 3.5"
R 0.75"
There is very little apparent backlash in the drive train and differential when viewed from under the car. Based on this information, I assumed the backlash was occurring mostly in the front of the transmission or the clutch. Last week, I dropped the transmission and inspected further. I found quite a bit of play in the clutch disk (3/4" at the circumference without any visible compression of the clutch disk springs).
video: http://dougtheelectrician.com/mercedes/clutch_backlash.avi
I bought and installed a new clutch disk, and guess what? Exactly the same symptoms, and nearly the same backlash measured at the rear wheel. I believe there is a very slight improvement, but it is hard to be sure.

I also have two other cars with manual transmissions which do not exhibit this behavior: A 1987 Caravan 5-speed, and a 1983 MB 240D 4-speed. I also jacked up and measured these cars, and they have very similar measurements to those above, although the Caravan's backlash doesn't change much from gear to gear and seems to be mostly in the drivetrain after the transmission.

My theory:
I am an engineer, so I am aware of the control feedback loop which travels from the driver's foot through the accelerator linkage to the injection pump, the fuel, the engine, the clutch, the transmission, the driveshaft, the differential, the CV joints, the wheels, the tires, the movement and speed of the car, the eyes (detecting the speed of the car), the brain, and finally back to the foot. The problem could be in any of these elements, although I think I have eliminated the transmission, clutch, drivetrain and brain (the cruise control does the same thing).

My appeal:
I would like to hear from folks who have a similar car and who don't have this problem at all, from folks who do have this problem, and especially from folks who have solved this problem.

Related thread:
My thread from last week about different clutch disks: http://www.peachparts.com/shopforum/diesel-discussion/272048-diesel-clutch-different-gas-clutch-why.html

Axles? I have a fair mount in my car as well. Does the 190D have a rear diff mount?

What is a rear dif mount?

Diff mount
 

OK, I think you are asking me if my differential is isolated from the frame with some kind of rubber mount. No, it seems to be bolted right up to the frame.

Reverse
 

I just found out another interesting clue. It is easy to make this behavior happen in first gear, but impossible in reverse.

so, im a little confused by exactly what the driving characteristics are problem wise. Can you tell me if this is correct, are you saying that in 2nd and 3rd, there is a problem with the smooth application of power?

Also, Im not sure that the backlash that you have measured in the drive train is really a "symptom" as related to power application. At most, you are talking 3.5 inches on the outside of a tire and you are measuring ring and pinion lash in the rear end, and gear lash in the transmission. The tire would be magnifying any movement as you measure the outside point of a large disc, plus movement like that is pretty standard on most cars IMO.

In fact, you've demonstrated it on your other cars, so that really rules it out as the cause I think, UNLESS you can find a worn U-joint or flex discs

From what you have written, could it be a binding throttle linkage problem? a sticky part where you can't give it just the right amount, and either give it too much or too little causing the car to buck? There have been lots of conversions that ended up needing a simplified throttle setup to address that. Maybe its on the throttle end and not in the drivetrain.

Can you describe the way it acts again?

Can anyoen confirm there is no rear diff mount? Even without a mount there should be bushings. I would guess these need to be replaced.

I think I know what you mean, I have a few manual 240Ds so I have something to compare. My Euro 85 (125K) will do that "springy take off" just as you describe but mine doesn't sound as bad as yours. It feels like weak clutch springs to me :confused:, my 79 (with 50K on clutch) will do it if I dont have RPMs up:eek: Its not a big deal and doesn't happen until I get sloppy with my shifting. My wife complained about it once, she pays more attention now:D

engine bucking continued
 

winmutt: There is no rubber shock mount for the differential. It bolts right to the frame without any shock isolation. It is isolated from the driveshaft through the rubber flex disk, and from the wheels through the CV joints in the axle.

dropnosky: The problem happens to some extent in all gears. It is not very noticeable in 4th and 5th gears because the engine cannot apply much force in these gears. It is not usually a problem in 1st gear, since most of the time the driver is accelerating fairly hard in this gear. To cause this problem in any gear, all the driver has to do is make an abrupt throttle change. At this point, I agree with you that it is probably not the drive train causing this.

I am starting to think this is a throttle linkage problem, or perhaps some strange inertial interaction in the injection pump or governor, but I don't see where it could be. All the linkages seem tight to me. It was at one time an automatic, and there was a linkage from the bottom of the injection pump down to the auto transmission, which I have removed.

I once had a similar problem in a 1965 Buick Special, and I discovered that one of the motor mounts was completely broken. I could stand in front of the car with the hood open and the engine running, and by "goosing" the throttle linkage with my hand, could make the V6 engine rise several inches out of its mounts. Because the throttle linkage was routed in from the side, this motion would reduce the throttle which would cause the engine to settle back down, which would increase the throttle, etc.... I don't think this exact thing is happening, since the motor mounts are new, and the throttle linkage, from the engine to the firewall, is a cable, not a rod.

Stevo, I just replaced the clutch. I am thinking how to make a video of this behavior. Maybe in the next couple days.

My 240D does something similar. I don't think it's a PIO. There's a window of throttle input through first gear that will not produce bucking, step outside and it bucks a lot, till you get to maybe 20 MPH. The damper on the IP linkage is toast, I just threw it out, might not hurt to replace it though. I think it's the motor bucking on soft mounts- if it suddenly generates a torque at the tranny output shaft, I think it starts rocking and bouncing off one or both of the mounts, probably enough to retard the drivetrain on one side of the oscillation. I always figured it was bad mounts.

It could be an oscillation based on bad input filtering. I don't know how or if there is any input filtering on the 190D. The 240D has a dashpot in parallel with the input linkage, so it's sort of one sided damping, keeping the input lever from rebounding if the throttle is suddenly released, but no impediment to a sudden throttle application.

I may be wrong, but pops told me that audi came up with throttle input damping to deal with bucking on front wheel drive cars. No direct linkage, but a spring / dashpot arrangement.

I had a pretty severe back and fourth jerking in my cars drive train after the conversion. It would only occur when i was above fifty, or backing off the throttle in fourth gear. Turns out that i did not line the two drive shafts up correctly even though i marked them. When i lined them up correctly it stopped completely.

I am sorry to say, I still haven't resolved this problem. Does anyone have any more ideas? Bump!

anti-jerk valve
 

I explained this problem to my local MB guru, and suggested we should take a drive. He said we knew exactly what the problem was without needing to experience it. Apparently, there is an "anti-jerk valve" installed on the injection pump of diesel MB cars with manual transmissions. There are three solutions:

1) just live with it by careful driving
2) find a injection pump from a car that was originally a manual.
3) find an injection pump shop to add the anti-jerk valve (expensive)

I am not sure how to take it, but my wife says sometimes she could use an anti-jerk valve too.

One last question: Does anyone know the German for "anti-jerk valve"

i want a picture of this anti-jerk valve! :)

240D manual dude here. ... (and it likes to buck from time to time. ... i just thought it was part of the experience.) who knew mercedes engineers had a valve for that?

I'd like to see a picture of an anti-jerk valve. Never heard of one on this forum before, except for the banning system typically exercised from discussion on the open forum.

The only vehicle I have ever had this on is a 1954 F500 Ford Stake bed with hydraulic lift gate on the back..

It only starting happening after I drug an 8 foot by 8 foot by 2 ft concrete block from the front of the property to the back... the long way to avoid messing up the driveway... close to 2000 feet....I had to keep going because I was at my limit for pulling it anyway.. I could not count on being able to stop and let stuff cool and get started again...
In other words... I burned the clutch and probably warped the friction disc part of the flywheel....

This is the same effect you get from warped rotors on disc brakes... a pulsing effect... It would not take that severe a situation to burn a car's clutch and flywheel...

Anti jerk valve??...Thats a new one one me, but theres never an end to learning new things about these cars. The only thing that comes too mind is the little "shock absorber" thing on the IP linkage of my later 123s. It does make shifting noticeably smoother. I think this is particular to manual cars but not sure. Certainly not in the "valve" category.

I noticed that some european model W123s with manual transmissions have a mini shock absorber mounted on the IP throttle linkage... so maybe that's the "anti-jerk valve".

Any news on the jerky IP?

So this car is a conversion from automatic and not a factory installed manual transmission. I wonder is the flywheel is a part of this; my understanding is that the flywheel is different from manual to automatic. Perhaps it supplies inertia where its needed? WOuld a heavier flywheel be a good thing or a bad thing?

the flywheel from an automatic could not be mated to a manual tranny so I dont think that could be the problem.

My former 190D 2.2 had the factory 5 speed. I had the damper on the throttle linkage at one time, but was removed. I only remember having the bucking problem a few times, so I was just a little more careful with the throttle and clutch.

Hi to all , I am new to this forum ,I fond this thread and I relait to the same problem , I have a 86 190D whit a 5 speed transmission so far I deed :
-Replaced Injection pump whit a rebuild unit.
-Replace injectors
-Replace chain tensioner
-Replace clutch / pressure bearing / pressure plate / shaft bearing
-Replace flex joint rear and front
-Replace center shaft bearing
-New shacks / new tires
-New motor mounts
-I remove the harmonic balancer from the shaft It was in pretty bad shape.
All the above done and I have the same problem.
I don't have a damper on the throttle linkage , I don't even have a mount for it .
tinker_er you have found the problem ?
I suspect the timing device but again just under 50% , this jerkin drives me crazzy .:hammer:

In Germany we called it the Bonanza effect.
I don't remember what Mercedes did to fix the problem.
I think they installed a damper/shock in the gas linkage somewhere on the injection pump.

I don't even have a mounting point for the shock :(

I get the same on my manual 240, my mech buddy also said weak clutch springs can cause that.
There is an "anti-jerk" shock on my IP.

anti-jerk
 

Also check the "butterfly" to make sure it is connected. It is the big flap in the air intake . . . if it is disconnected, it will cause that symptom also. I had a valave job done, replaced the timing chain and components, and a clutch job done all at once, and the mechanics forgot to hook some things up. Consequently, I had some jerking motion going on. Once we hooked up the "butterfly" everything smoothed out. Also, is it possible your cruise control is stuck "on."?

You/ve gotten some good responses in this thread.

Start by putting a floor jack under the front of the differential, not on the flange, but the case, and GENTLY lift upwards. Do not raise the car with it, just lift upwards and see if you get much movement. If you do, the problem is your differential mounts.

Also check your rubber driveshaft discs and u-joint.

I have the exact same problem with my 1984 190D. Have 5spd from the factory in mine. Have not solved the problem. Usually avoid it by careful driving. I like the idea about the small damper in the throttle linkage.
Was thinking about changing the flex disks probably would not make difference though.

What that "butterfly" do ? and who regulates it?
-----
Thx Larrie,
I am gonna check that , my flex joints are brand new.

Butterfly
 

[QUOTE=razvy;2817475]What that "butterfly" do ? and who regulates it?
-----

The "butterfly" is a big flap that opens and closes, like a venetian blind and controls the amount of air that comes into the cylinder. If I remember correctly, yours is at the back of the engine, on the end of the air intake intake (outside of your filter housing). It's supposed to be in the closed position when the engine is cold, and open up when the engine warms up. If not attached, it will flop around, choking off your air when inappropriate, making the car jerk. It's a similar system to carburation butterflies at the top of carburators, attached to a choke selinoid. Look for the scoop coming from the filter housing, and look inside that scoop. Make sure it's hooked up to a connector wire/linkage, keeping it from flopping, follow the connections/linkages and make sure it's connected throughtout and not floppy. You can also try to block it open, as a test, and try driving it to see if the jerking continues when it's blocked open. If the problem goes away, you know that was the problem.

You might also want to get the car on a rack, put it in the affected gears, try turning the back wheels to find out if there's "flat spots" with harder turning, in which case, you're in for a tranny rebuild for new bearings. You can probably get a tranny shop to give you a free diagnosis. Also, what condition was the throwout bearing in, and the fork??? The other posters have given you directions on checking the rest of the drivetrain. Remember . . .isolate, and check and work your way through the entire system until you find the problem.

Also, a little known about possibility. Was the timing chain and all components replaced??? If it's the 2.2L engine, those engines were also used in reefers and had a different system setup. If the wrong one was used for R & R, it would cause that problem, but I would think it would happen in all the gears. Might be solved by replacing the timing chain with all components (correct one for auto use), or by adjusting the timing.

Go through the rest of the recommended checks first before delving into the timing, however. Which engine do you have??? the 2.2L or the 5-cylinder 2.5L, or the 6-cylinder?

OH, I forgot another thing: When the conversion to manual tranny was done, was the rear end replaced with it??? I believe the gear ratios are different for the the manual tranny version, in which case, that might be a problem.

Also, there is an engine shock in the front of the engine which IMHO is a real PITA to replace. Fairly cheap part, though. However, mine was flat for years and only cause rough idling.

I have the 2.5 5 cylinder , the fork is fine and throwout bearing is new whit pressure plate a new clutch ( under 500 miles) .
I am going to check on that butterfly in few minutes and I let you know what I found , I have a ? who controls the vacuum solenoid ?
--
No this car was original 5 speed manual , but the engine was change from a automatic , I don't have the dampener road on the IP , I was look in for the bracket and deaden find it , the injection pump has a empty place to attached something .

What engine shock? at the belt tensioner ? That is been changed.

It wouldn't hurt too include the model MB in a signature so folks with faltering memories wouldn't have to go back to the beginning.:)

I 've seen this flap on the early W115, 240D engines, but didn't know the W190 engine used them.

The "spingie feeling" I sometimes get with my 85 feels like weak clutch disc springs. Good luck

190D
 

Yes, the 201 did have the butterfly. I discovered it when a mechanic and I tried to find out why my '84 190D, 2.2L, 5-spd was driving like a real dog after all the work completed - valve job, new clutch. The butterfly was one of those things not reconnected and we had to fashion a new linkage for it. Also, my non-working cruise control actuator never made it back into the engine compartment, which was fine by me, but had nothing to do with it's poor performance. However, I would try to totally disconnect yours, in case that is a problem. Sometimes, when I use it on my 300D, it will also cause that same jerking motion, even though I have an auto tranny.

You right Stevo , I well add to my signature .
I went outside and deed some checking :
The vacuum module in top the air filter is OK , i apply vacuum whit a mityvac and hold vacuum and operates the gate ( butterfly) .I remove the air filter and visually inspected and is OK.
I started the engine (outside temp 49º) and the module doesn't move , I check for vacuum and I don't have any ( zero) , I follow the lines and end up to a vacuum distribution vale in front of the battery ( passenger side) and i have vacuum going in but none going out on all the lines .

butterfly
 

so . .. warm up the engine and see if it opens up. If it does, it's working correctly. Or you can disconnect and freeze it in open position for test drive after it's warm. If the jerking goes away, you found your problem. If the problem is still there . . . hook it back up again and look for the next possible cause.

Yes, that is the engine shock I was referring to earlier. If it's new . . . obviously not the problem.

Right now it s in a open position , I am doing the test in a few minutes . I am curious to see if it get any vacuum , so far as I explain is dead .

I when for a test ,
Whit the vac. disconnected the butterfly is open( relax mode) and the car dose the same, then I apply vacuum whit a T and butterfly closed, I deaden notice a change in the engine sound or rmp , the car improve a little but the jerkin is still there .
Regarding that butterfly suppose to stay close during normal drive ?
The EGR valve can produce this symptoms ?

@Stevo
I added the car to my vehicles and deaden appear as my signature , where is that section ??
Thx

I had it too
 

After I did the 5spd conversion on my 190d it would exhibit the bucking behavior. I quickly learned to adjust my throttle foot to prevent this , not sure exactly what but it was 100% effective. I actually forgot about it until someone else drove the car. Cheers Dan

Not sure, the User CP, I would think

I am thinking the rear axle shafts , wear on the joints can produce this jerkin what you guys think ?>
Take a look at this video at min 3:00
Rear Axle Shaft Inspection & Repair on a Mercedes Benz by Kent Bergsma - YouTube

Did you every figure out the problem?

I have the same issue, part throttle, high load and its almost as if someone is engaging then disengaging the clutch over and over again causing it to oscillate back and forth getting worse and worse.

Letting off of the gas causes a considerable jerk, and getting back into it again does the same...

I was also wondering that, I think its the springs in the clutch disc getting weak. My 240D does the bucking thing under certain circumstances with about 50K on the clutch.

Well that's not promising.

I was hoping it may be the rear trans mount which seems a tad squishy. I will probably replace that first but need to find the proper part number for a Manual Trans mount.

I just don't want to spend more than what I paid for the car replacing all of these related components only to still have the same problem. Maybe I need to see if it's this anti jerk linkage which I don't have connected. But like OP said it happens with cruise control so it seems unlikely.

It also happens if you upset the car by hitting a pot hole or something else, but the main trigger is switching from accelerating to decelerating or vis-versa. Letting off to coast for a second then getting back into it really gets things shakin, you need to floor it to take up slack, or oscillate the pedal at a different frequency to cancel it out. Or of course trim it out with the clutch.

Has anyone figured this out yet?

Went out jacked the car up on one side in gear E brake down. could turn the wheel about 1/8 of a turn! and driveshaft to diff had about 1/4" play.

I think my original thought was right, and the diff is the problem. I know someone said bearings would wine with that much backlash, but I'm guessing that happened a Looooong time ago.

in gear you can roll the car back and forth several inches.

that doesn't sound necessarily alarming

I know that doesn't sound like much but it translates a lot over the whole car. I have actually never seen a car move that much in gear before

I also notice when IN gear there is not much play at all in the shaft, but out of gear a LOT of play before the shaft turns the wheels.