VW Passat Automatic Transmission Clutch Not Disengaging

Hello, I'm having a problem with my Passat 35i. It was manufactured in 1995, engine code: AGG, and transmission code: CLK (automatic).

The background story:
About two weeks ago, I drove my Passat through a red light and braked. Just as the car was about to come to a stop, it simply turned off. So, I put it in neutral, started it again, and when I tried to put it into gear, the car lurched forward and then stalled again.

Conclusion: The temporary coupling is no longer disconnecting.

Error memory is empty.

I then flushed the transmission with fresh ATF for about an hour (using an automatic transmission flush machine), as I suspected that the old oil might be causing the problem, and I replaced the filter on the automatic transmission. Unfortunately, it still has the same issue as before.

Okay, I disconnected the transmission speed sensor because without its signal, the clutch bypass doesn't engage. No luck, same result as before.

Then I disconnected the engine control unit (ECU) to simulate an emergency mode: no change, it's still the same as before.

I would now rule out an electrical fault. I suspect that somewhere within the transmission, an oil channel is not being properly connected or is completely blocked.

I seem to recall that Volkswagen has a repair manual that describes how to measure the individual transmission pressures. Unfortunately, I don't have access to that manual.

"Does anyone happen to have any idea what the problem might be, or know of any repair instructions, or have any other suggestions on how I can get my Passat driving normally again? I'm grateful for any advice."

Sincerely,
Benny.

Unfortunately, I'm not very familiar with automatics.
What did the oil look like? Were there any shavings visible in the automatic transmission filter?
Perhaps someone with expertise in Automated Testing will recognize this error.
Or visit an automatic transmission repair shop near you.

Well, the oil looked black, and there were metal shavings on the magnet in the oil pan, but it was all within acceptable limits. The problem appeared suddenly.

I don't even need to go to the transmission specialists; I already know the answer. (They would require me to bring the transmission in, etc.).

I'm going to visit my former workplace at Volkswagen next week and hope that they haven't disposed of the documents related to transmission specifications.

Hello.

The WÜK (converter disconnection coupling) always disengages when there is no oil pressure.
It is located in the impeller and connects the pump wheel directly to the turbine wheel when pressure is applied.
This establishes a direct mechanical connection between the drive side and the output side.
Unless.
- The storage in the converter is defective.
- There are debris particles inside the casing (between the turbine wheel and the impeller).
because it can jam the gearbox or the wheels.
Your symptoms suggest a faulty torque converter rather than necessarily a defective transmission. It's possible that replacing the torque converter will resolve the issue.

Lift the car up on a lift , making sure the wheels are free, and try to see if the transmission shifts smoothly. If it does, you'll know what the problem is.

Regards, Mpire.

The car shifts on the lift, but it also shifts while driving (though somewhat harshly). It goes through all the gears. I guess I'll have to remove the transmission and take a look at the torque converter. Thank you very much for your reply. I will let you know how it turns out.

Okay, so at least it's a small success – you now know that the transmission is working reasonably well.
The harsh shifting is caused by the "blocked" torque converter, because during gear changes, the TCU briefly disconnects it.
The converter then allows the transition to "glide," after which the power supply is reconnected.

Whether you install a new or a used converter depends on the specific situation.
Mileage, how long do you plan to keep the car, its value based on condition, budget, mechanical skills, workshop equipment, etc.




Regards, Mpire.

Quote:

Whether you install a new or a used converter depends on the situation:

If there are shavings circulating, the situation becomes critical. In that case, they absolutely must be removed, which means a complete disassembly including all connections, and a thorough cleaning is necessary.

Well, of course, the car is worth nothing now. But I'm also too sad to scrap a "rust-free" Passat from 1995 with 150,000 km on the clock, which is otherwise technically in good condition.

The necessary knowledge and a fully equipped workshop are available; success should not be hindered by these factors.

As I said, when I have a quiet moment, I'll take the transmission out and examine the torque converter and the transmission itself.


I will report .

Quote:

during gear changes, the TCU briefly disconnects. The converter then allows the transition to "glide," and the main circuit breaker is closed again.

Here's a possible explanation for the problem I'm currently working on with a 3B engine. When shifting from lower gears, the engine briefly revs up during the shift process and then is abruptly "cut" or limited.
The effect is less pronounced when the acceleration is greater.

@vwSchrauber

When was the last automatic transmission service performed on this vehicle?

Okay, here's the translation:

"I mean doing it properly: draining the oil, removing the oil pan, replacing the filter element, reassembling everything with new seals, and filling it with the correct amount of oil according to the specifications (temperature read via VCDS)."

If the transmission fluid level becomes too low, or if the oil pump cannot draw up enough fluid, then under certain driving conditions, the oil pressure or the amount of oil may not be sufficient to ensure smooth gear changes.
This becomes noticeable when the suction filter (filter element) in the oil pan is already quite tight, and the pump can no longer receive enough oil.
When accelerating more aggressively, the "behavior" is suppressed by a slightly higher rotational speed at the input shaft/pump and the increased torque that needs to be transmitted.

Cheap solution: Try topping up the oil.
Good solution: Perform an oil service including filter and oil replacement.

Regards, Mpire.

Quote:

When was the last automatic transmission service for this car?

Brand new replacement gearbox installed, but the problem hasn't been fixed.

Quote:

I mean it literally: drain the oil, remove the oil pan, replace the filter element, reassemble with new seals, and fill with the correct amount of oil according to specifications (temperature as read by VCDS). If the oil level in the transmission is too low, or if the oil pump cannot draw up enough oil, then under certain driving conditions, the oil pressure or the amount of oil may not be sufficient to ensure smooth gear changes. This becomes noticeable when the suction filter (filter element) in the oil pan is already quite tight, and the pump can no longer receive enough oil. When accelerating more aggressively, the "behavior" is suppressed by a slightly higher speed at the input shaft/pump and the higher torque that needs to be transmitted.

Oil quantity is correct, new suction filter, free of debris/metal shavings.

I have another suspicion – I'm currently investigating it.

"Error found: The vehicle has a different engine control unit (ECU) installed, where the pump voltage and the lookup tables for fuel cut during upshifts and downshifts are not compatible with the transmission control unit."

Lookup tables adjusted -> works

Thank you for the feedback.

I'm chiming in here because I seem to be having the same problems as "Hans Dampf" – apparently, the waste heat utilization system isn't disengaging at low engine speeds.

I have a Range Rover II/P38 2.5 TD with a BMW M51D25 engine and a ZF 4HP22 automatic transmission. The engine stalls, especially when the (transmission) is warm, and it's worst in reverse.

I'd be interested to know what turned out to be the problem with his transmission. Did he have to replace the torque converter or something else?

I've been to countless workshops, and I've asked in Land Rover, Range Rover, and BMW forums, but no one could figure out what was causing the problem based on the symptoms. I'm slowly coming to the conclusion that the torque converter isn't getting enough oil pressure, which is why it's not disengaging. However, I don't know whether I should replace the torque converter, the pump in the transmission, or have the transmission flushed... Everything has been recommended to me, including replacing the fuel injection pump. And most people say, "Well, let's just replace xxx and see if that helps." But that doesn't really help me.

The engine runs great, with no jerking or vibrations. The transmission shifts smoothly and at the right times. The wastegate also functions as it should, engaging around 80 km/h in fourth gear and disengaging when I slow down, both in fourth and third gear. However, it doesn't engage at idle speed.

Perhaps someone can give me a tip?