Does a torque Convertor ever fail? And if so, what is the failure and what symptoms would the driver experience?
Cheers,
Jeff

 

Yes torque converters do fail as do all other parts of a vehicle. It's not a question of "if" but "when". Having said that I cannot speak specifically of MB torques but of torques in general. As I'm sure you know the torque is there to "slip" when the vehicle is stopped in drive so that the motor doesn't stall.

Inherently a torque is a "slip" part. Each torque is designed to lock up at a specific RPM. Typically the full "lock up" is in the 1000 to 1200 RPM range. When a torque fails the lock up occurs later and later until finally the torque will not lock up at all. The other end of the scale is also possible in that a torque could fail to slip resulting in a motor stall situation.

What symptoms are you experiencing that you believe may be related to the torque converted? There are a lot of well experienced folks here that may be able to help once they understand your problem.

 

Thanks Bobby for the response. In my S55 (722.6 tranny), I get severe vibration at ~2,200 RPM, regardless of the gear. It is not related to ground speed, but RPM. Thus, the cause of the vibration is somewhere before (roughly) the planetary gears in the transmission. I have replaced engine & tranny mounts twice already, each time it only masks the vibration for about a year. I just replaced the engine vibration dampener, with little change in the vibration. The engine is strong, suggesting timing, etc. is in good shape. When the vibration occurs, there is no odd sound (knocking, clanging, tinging, etc.); just severe vibration. This suggests something out of balance as opposed to a bearing. Idle is smooth, as is acceleration. Once the engine RPM hits ~2,000 however, the car starts to shake. First, second, third... doesn't matter. Vibration is very repeatable, though much worse when the engine/transmission is cold. From a standing start, WOT acceleration is strong but the vibration seems reduced considerably. However, this may be simply a matter of the engine torqued all the way to the extreme on it's mounts. That said, the transmission does have some funny slippage in first gear and unless I'm WOT, automatic gear shifting through all gears is not as crisp as I have had in other MB's. My SL600 is a perfection of shifting, for example.

So step 1 was to change (again) transmission filter/fluid, just to convince myself it was done correctly. (MB dealer did the previous change.) Lo and behold, as I was rotating the crankshaft to find the torque convertor drain plug, I came across a big white 'X' that had been written on the torque convertor. Why would a TC have an 'X' written on it in white ink? That got me to thinking about the how a TC could fail. BTW, changing the filter/fluid helped a bit on the shifting, but the vibration remains. And interestingly, the TC does not have a drain plug. Not a complete surprise, but I was expecting one.

Is it possible that a TC could fail in such a way that it's pressure could oscillate at a particular speed? I looked for evidence of a missing counterweight, but didn't see anything out of the ordinary. Mounting bolts, etc. look as if they have never been removed. (Thought maybe a previous owner swapped out a faulty TC.) Transmission pump? Solenoid valve? Automatic transmission theory was never my strong suit. LOL

Thanks for any additional input you might have.

Cheers,
Jeff

 

If I had to guess I would say that your problem is forward of the torque converter. "Changing the trans and motor mounts masks the problem for a while" tells me that the vibration is probably coming from up front. It could be the flex plate where the TC is attached to the crank shaft; it could be one of the pulley on the front of the engine; it could be ignition related (coil/plug) etc. You don't mention if the vibration goes away after 2000-2200 RPM.

I can think of nothing internal in the transmission that could provide the symptoms you describe.

It could also be drive shaft irregularity - weight missing bad U-joint/CV joint. If something had changed in the rear end geometry due to an accident or running over debris on the highway a vibration could result. I've seen driveshaft angle to the differential cause weird problems such as vibration.

My best advise is to find a good Indie and further isolate the problem. I doubt that the transmission will end up being the culprit. Good luck on the repair.

 

I have stock and after market convertors if you are interested.

 

Thanks Shardul for the info. Still trying to determine if the TC is the issue.
Cheers,
Jeff

 

If it has a vibration (and you have ABC suspension) and does it do it in park/neutral around 2100 rpm? If so I would replace the pulsation damper between the ABC pump and the first valve block.

A torque convertor clutch on a 722.6 will typically cause the most vibration around 2000rpm in 3rd gear whilst on a slight incline. Doe it vibrate at higher rpms too? What brand gearbox mount did you use?

 

Thanks Aus-MB-Tech for the thoughts. The ABC Pulsation Dampener (or 'bulb') was replaced last year due to the infamous ABC drone that occurs. No change in the car's vibration, even though the droning noise disappeared.

Interesting prediction! Yes, my vibration is probably most severe in 3rd gear, at ~2000 RPM. However, my vibration varies... WOT has less overall vibration than steady, easy acceleration. Wind the engine up, allow it to hit higher RPM's, and the vibration is much reduced. Haven't noticed any difference whether inclined or not; though never thought about that aspect. 'Easy' acceleration causes the most vibration; hard acceleration the least.

Doesn't seem to vibrate at higher RPM's. One would naturally think of the harmonic of ~4000 RPM, but this may be because the engine is working harder at that RPM; pushing against the limits of the mounts.

In both replacement cases, I installed genuine MB mounts, from the dealer. Thank goodness I get them wholesale!

In your mind, what do you see as the potential failure of the torque convertor? How does it fail?

Cheers,
Jeff

 

This thread has inspired me to pose a question about a similar problem I have been having with my 2000 C280. When the transmission is cold there is a brief rumble from the torque converter clutch at 35-40 mph (transmission is in 5th gear at this point). The clutch will go into "lock up" briefly, rumble, then disengage. This can be observed on the tach. When fully warm it goes away. At about 100,000 miles, while under CPO warranty, the dealer replaced the valve body and loaded a software update. It cleared the problem for a while, but it came back. I "work around" it by selecting a lower gear until the transmission is fully warm. However, as the miles have accumulated (the car has 206,000 miles now) I have to keep it in the lower gear longer. Also, the problem never occurred in summer months before, but now happens year 'round. I have considered replacing the converter; a reconditioned converter from the dealer is reasonable priced. The transmission shifts fine otherwise and I have changed the fluid and filter periodically and have found very minimal sludge and no debris. Is it worth it to try the converter replacement?

 

I assume you have checked all 4 tires and wheels.

 

[QUOTE]I assume you have checked all 4 tires and wheels./QUOTE]

I don't understand what you are getting at. As I stated, this has been occurring to some degree for over 100,000 miles. Several new sets of tires have been installed in that time, and I actually replaced the original wheels with new factory wheels because the finish on the originals was bad. Furthermore, the dealer diagnosed the problem as the converter clutch and solved the issue for a time.

What has me stumped is that I don't know if simply replacing the converter will resolve the issue (if perhaps the clutch is glazed as it could be in a manual transmission application), or if something within the transmission is causing it (deterioration that is causing the pressure that actuates the clutch to drop over time perhaps).

 

Have you had a oil sample from the gearbox analysed? Very uncommon on a W220 but worth checking if contains high levels of sodium or water (coolant). You may have a leaking transmission cooler causing damage to the torque convertor clutch pack. You only notice to torque convertor clutch because it never locks completely in a 722.6, it slips between 10-120rpm whenever it's engaged. Burnt or coolant damaged clutch linings will then shudder.

There is also a possibility that the linings are just worn and can no longer be applied strongly enough (the piston bottoms out before it gets enough pressure on the clutches).

Either way I think you'll need to get a rebuilt torque convertor fitted (no need for a new one). Do the oil test as it'll tell you if you need to replace the radiator or not.

 

OK, Aus-MB-Tech... You've teased us long enough! Clearly, you've had some experience(s) regarding 722.6 torque convertor failures. In my case, you were very close on the prediction. So, what is the specific failure of the torque convertor that causes our symptoms? In my case, the tranny fluid is clear of coolant and metal. I just have this vibration or 'shuttering'. And yes, there is a little vibration at the 1st harmonic (~4,000 RPM), but not as bad as at ~2,000RPM. And 3rd gear is clearly the worse gear. My query here is more for future prevention.
Cheers,
Jeff

 

Checking the gearbox oil for coolant isn't a visual one, it takes very very little coolant to do the damage thats why oil analysis is the best way. Basically the coolant is absorbed by the clutch linings and displaces the oil that they usually absorb. This allows the clutches to burn and have a inconsistant friction value (imagine having a juddering clutch in a manual and trying to do a smooth start off). The main clutch packs don't get too affected by this as they don't stay in the slip phase for very long where as the TC clutch stays in the slip phase most of the time. The damage is there but you'd need alot of coolant to notice the damage in the rest of the gearbox.

The other reason they shudder is when they wear out. This is more common on lower powered engines and more unlikely on a S55. The reason low powered model are more affected by wear is because they have less clutch linings (maybe only 1 or 2 instead of 3 or 4). They don't fully wear out but to combination of less linings and wear allows the lockup clutch piston to bottom out before it can get a high enough clamping load. One of my cars has this at the moment that I need to get around to fixing. 1998 C240, drives perfectly until you put a box trailer (even empty) on the back. When I add the trailer the TCU needs to apply more pressure than normal to get the TC clutch to to correct slip speed (10-120rpm), as it's worn it cant get enough clamping pressure and the slip speed increases to 200-500rpm which causes a pretty noticable vibration. My fix is simple for the C240, rebuild the TC and It'll be back to normal.

 

Did you solve this?

 

Replace the pulsation damper in the ABC suspension, gives weird vibrations at 2000-2200 rpm, it would be stuffed by now anyway.
It's located near the steering rack.

 

Hi Jeff,
What ended up being the solution to your problem?

 

I hate threads like this with no updates.

 

And most likely if the vibration happens when the car is rolling at a certain speed, a vibration can be such things as tires out of balance, tires with blisters, a drive shaft problem, or rear end half shafts if independent rear suspension. If a torque converter is out of balance you can sit in park or neutral and rev the engine up and down and could feel the vibration you don't need to drive to feel that. Also vibrations can be the engine it self, and things like a miss fire or any thing that causes rough engine operation.

 

 

Try new sparkplugs and re seal the top of your motor (valve covers, supercharger etc)

 

 

 

Thought to post my problem after seeing the engagement of this post. Got gearbox and torque converter repaired and there was an unusual jerk while driving and handed it back to the workshop.

Now the ride is extremely smooth. Don't feel any gear change or torque converter locking/unlocking. However, I noticed a weird thing which wasn't there earlier. Car revs more than 4500 ~ 5000 if i push the pedal, which wasn't the case. Also I feel the same pulling power isn't there. Any suggestions to start looking at?

 

Hi Folks,

Frustrated with my problem which sounds similar

1. New plugs, coils , air filter etc
2. car just seems it has no torque or pull
3. did TB adaptations also
4. Fuel pump swapped but no difference
5. throttle body swapped no difference

my issue is as I shift gears in S+, from 2-3, the car bogs down for few seconds and shifts to 4th. As I shift from 4th to 5th, I have the same problem, it bogs down. Funny thing, on hard deacceleration at times, the car just stalls....no response from the throttle for a few seconds and then the car is back to normal. NO CEL. That’s the wierd part.

could it be the torque converter ?