Clutch slipping

[Dimokslis]

Hi there, Could everyone help me with CVT problem? When I bought car it did not have forward gear, I opened gearbox and found one pipe broken (0AN301541C). I have replaced it with new one,filled with new oil, but did nothing else to the gearbox. Unfortunately it did not help at all.
I added VCDS read out channels 10,11,12. Any help is much appreciated.

[Horch]

Hi,

have you checked the TCM for error codes? The gearbox has two sets of clutches. One for forward, one for reverse. Both are controlled independly. The reverse clutch is more rigid due to its greater diameter. If you have no propulsion in R, it is likely that the input shaft is broken. As you have opened the gearbox to exchange the pipe with valve you have removed the hydraulic unit with the pump and the drive chain as well. I assume that both parts were well inspected and found ok.

Beside the input shaft there is a good possibility of a valve malfunction in the hydraulic unit. But that requires an in-depth inspection.

Regards,

Horch

[Dimokslis]

Thank you for your response. Yesterday I had 2 fault codes:
001826 - Transmission Output Speed Sensor (G195)
P0722 - 000 - No Signal - Intermittent
Freeze Frame:
Fault Status: 00110000
Fault Priority: 0
Fault Frequency: 4
Mileage: 161183 km
Time Indication: 0
Date: 2018.03.01
Time: 13:55:02

Freeze Frame:
RPM: 960 /min
RPM: 0 /min
(no units): 13.0
Torque: 4.0 Nm
Temperature: 8.0°C
T.B. Angle: 0.0°
Bin. Bits: 0101 0 0

006035 - Transmission Output Speed Sensor 2 (G196)
P1793 - 000 - No Signal - Intermittent
Freeze Frame:
Fault Status: 00110000
Fault Priority: 0
Fault Frequency: 4
Mileage: 161183 km
Time Indication: 0
Date: 2018.03.01
Time: 13:55:02

Freeze Frame:
RPM: 960 /min
RPM: 0 /min
(no units): 13.0
Torque: 4.0 Nm
Temperature: 8.0°C
T.B. Angle: 0.0°
Bin. Bits: 0101 0 0

I have not reassembled any other parts, including valve body, I just changed the pipe and refilled with new oil. Inside every part looked like new, no marks or anything else. Reverse gear works fine from what I can see.
Is there any way of telling why has that pipe broke?
And is it fairly easy to check valve for malfunction? Or is it specialist only job? I have fully registered VCDS software if that helps. Thanks for helping me.

[Horch]

Hello,

the value in MB 10 is way too high. Should be in the range of 0,310 A to max. 0,350 A. Any value above 0,310 A indicates a leakage from hydraulic pump via jet suction pump to the forward clutch. This can be compensated to a certain extend by adaption. If the leakage is too high, the forward clutch can not be closed.

The pipe you have changed is for the ATF return line from the ATF cooler, which is integrated in the motor cooler. This pipe is only exposed to low pressure and no mechanical stress.

In MB 15.3 and 15.4 you can check the actual value of clutch pressure and the clutch pressure setpoint value.

Is it possible that someone has already opened the gearbox and re-assembled the wrong way? Maybe also forgot some sealing and/or removed something from the input shaft? That could also be an explanation for the damaged pipe.

The two fault codes indicate a defective TCM, if the sensor wheel of the output shaft was replaced and mounted correctly. But even with this faults the car should drive forward and are not the root cause.

Regards,

Horch