[heze]

Good afternoon all,

My ZF 8HP45 automatic transmission has a problem: when the oil is cold (within first minute after start driving), sometimes the transmission shifts down by itself without reason.

In the higher gears I notice this on the RPM gauge of the engine, which increases rapidly, but when it happens from the second to first gear during acceleration, you are happy to wear a safety belt... This cannot be good for the internal parts of the transmission.

As soon as I drive about three miles, the problem does not occur anymore.

In ISTA there is no error code present. Because this car has quite a history, I already changed the following components on the automatic transmission because of water ingress:

- New clutch plates on all clutches
- Professionally rebuilt torque converter
- Replaced the mechatronics incl solenoids (my own TCU is re-used because of internal immobilizer).
- New oil seals
- New oil + filter
- I tested a second hand gear lever with no luck

All repairs have been done in the last 500 miles. The transmission looks new inside. It also shifts like a dream (apart from the hickups now and then).

I'm running out of options now. I have the bad feeling that it can be something in the electric circuit (wiring, power supply, TCU).

Strangely I cannot find anything on the Internet about this failure. Is there someone with a similar problem?

Many thanks in advance,
Best regards Hendrik.

[anjuna]

Hendrik,

To be clear, this is only when kalt?

The TCU does hold gears for longer when cold and does not shift to overdrive as easy.

I am understanding that you are having issues with very very hard shifts. Do you have the ability to log this issue with MHD or BM3?

Thanks for your time

[Moisture]

Are you sure your solenoids are functioning as needed?

[Diawal91]

Originally Posted by anjuna

Hendrik,

To be clear, this is only when kalt?

The TCU does hold gears for longer when cold and does not shift to overdrive as easy.

I am understanding that you are having issues with very very hard shifts. Do you have the ability to log this issue with MHD or BM3?

Thanks for your time

+1

[heze]

Originally Posted by anjuna

Hendrik,

To be clear, this is only when kalt?

The TCU does hold gears for longer when cold and does not shift to overdrive as easy.

I am understanding that you are having issues with very very hard shifts. Do you have the ability to log this issue with MHD or BM3?

Thanks for your time

Thanks for your answer,

Yes it only happens (sometimes, not always) in the first few miles when the car is just started up...

When this problem occurs in the second gear (it shifts back to the 1st gear), the car (X5, E70, N55, about 2300kg) is braking very hard on the engine. Sometimes it happens in higher gears, but the braking effect is much less severe in this case.

I have an ICOM cable, ISTA-D, ISTA-P, WinKFP, NCSexpert, Tool32 and I'm familiar with these tools.

What are MHD or BM3? Logging software?

EDIT: I searched for MHD and I already have a K+DCAN cable. When I buy a USB to USB-C adapter, can I connect this cable to my android phone and log variables with MHD? I see that I need to buy a license of 69 dollar for logging purposes, which is not a major problem, but I need to be sure that MHD flasher really helps in fault finding.
What do you want to log? Gear status?

Thanks again for your response!
Best regards Hendrik.

[heze]

Originally Posted by Moisture

Are you sure your solenoids are functioning as needed?

Thanks for the response,

I'm pretty sure that the solenoids are in good condition.
I replaced the mechatronic including the solenoids, and the symptoms did not change after the swap.

Best regards Hendrik.

[heze]

Good afternoon all,

This week I had the same problem again, and this time a number of errors were shown on the i-drive: DSC stabilisation was disabled and and the LED in the gear lever was flashing.

I connected ISTA-D and one of the errors was:
12301 unzullassige abweichung von abbtriebsdrehzahl und raddrehzahl
12301 Inadmissible deviation between output speed and wheel speed

Now we are getting somewhere... the output speed of the transmission does not correspond with the wheel speed.

Is there a possibility to log those parameters for longer time? MHD flasher is able log parameters for the engine, but can it also log parameters for the rest of the car (transmission, DSC)?

Does anyone know another app which can log can-data from the car?

Thanks in advance and best regards,
Hendrik

[Moisture]

Originally Posted by heze

Good afternoon all,

This week I had the same problem again, and this time a number of errors were shown on the i-drive: DSC stabilisation was disabled and and the LED in the gear lever was flashing.

I connected ISTA-D and one of the errors was:
12301 unzullassige abweichung von abbtriebsdrehzahl und raddrehzahl
12301 Inadmissible deviation between output speed and wheel speed

Now we are getting somewhere... the output speed of the transmission does not correspond with the wheel speed.

Is there a possibility to log those parameters for longer time? MHD flasher is able log parameters for the engine, but can it also log parameters for the rest of the car (transmission, DSC)?

Does anyone know another app which can log can-data from the car?

Thanks in advance and best regards,
Hendrik

Unless maybe you did not replace all the solenoids (and left behind a faulty one) then the only other possibility is a problem with your TCU.

However, it could also be a problem with your transmission fluid level. You might want to double check that.

[heze]

Thanks for your reply.

The transmission fluidlevel is also ok.
I'm affraid that one of the speed sensors on the TCU is damaged.

I also saw that changin the ISN of the 8HP in E-series is very difficult, so replacing the TCU for a second hand one is not possible. Is my only option to buy a mechatronic from BMW (around 3600 euro)? A new TCU cannot be bought from BMW as far as I know...

To be sure which sensor is damaged, I want to log the speed data from the CAN-bus. I discovered the program TESTO, but this app is mainly intended for the engine parameters, and not for other ECU's.

Does anyone know whether there is an app which can read CAN-parameters other than the engine and store it to CSV file?
The requested parameters can be made visible in INPA, but INPA cannot store the data as far as I know...

Thanks again!
Best regards Hendrik

[Moisture]

Originally Posted by heze

Thanks for your reply.

The transmission fluidlevel is also ok.
I'm affraid that one of the speed sensors on the TCU is damaged.

I also saw that changin the ISN of the 8HP in E-series is very difficult, so replacing the TCU for a second hand one is not possible. Is my only option to buy a mechatronic from BMW (around 3600 euro)? A new TCU cannot be bought from BMW as far as I know...

To be sure which sensor is damaged, I want to log the speed data from the CAN-bus. I discovered the program TESTO, but this app is mainly intended for the engine parameters, and not for other ECU's.

Does anyone know whether there is an app which can read CAN-parameters other than the engine and store it to CSV file?
The requested parameters can be made visible in INPA, but INPA cannot store the data as far as I know...

Thanks again!
Best regards Hendrik

See if BMW will remap your transmission first. Or speak to someone who can reprogram it .

[BMdoubleU X5]

Hi Heze,

I was wondering if you have find what the problem.
I have a similar issue.

here from you soon.

kind regards

[heze]

Good afternoon,

Yes the problem turned out to be a faulty ABS sensor. The sensor itself worked well most of the time (without fault codes), but once in about 10km it lost a pulse, resulting in a smaller speed reading for a split second, causing the transmission to shift back 2 gears. After the split second the transmission shifted back to its original gear.

Best regards Hendrik.