Thread: Td5 Autobox downshift clunk!

The fact is that all the valeus shown by nanocom are addaptive and comparing with others might not be very relevant but i have a strong feeling that if any reading is out of accepted range you'll get warnings and fault codes so if there are'nt any faults logged in the EAT ECU the electronic side should be good IMO

Sierra I agree that if the values were out of normal range they should raise an alarm but that alarm would have had to of been programmed into the ECU. I believe the boss unit probably is quite good and all relevant alarms be programmed.

However I am still interested in knowing what those values are on other people people vehicles. It is perhaps possible that the value displayed is in fact a constant and not used by the autobox when mated with this engine ECU.

I'll try and remember to have a look at what mine is doing tomorrow, Ceebrady. In the meantime, I agree with Sierrafrey that it is more than likely a mechanical fault than an electrical fault. I understand your motor has an interesting history, but I would think you'd see more issues with shifts across the board if there were dud sensors or default values being used. The one time you'd expect none of that to matter would be at idle, and when starting and stopping.

I found simply putting the gearbox and transfer case in neutral, handbrake off, I could manually twist the driveshafts enough to hear any slop in the system. Just make sure you chock the wheels when doing this!

Originally Posted by Cebrady

Sierra I agree that if the values were out of normal range they should raise an alarm but that alarm would have had to of been programmed into the ECU. I believe the boss unit probably is quite good and all relevant alarms be programmed.

However I am still interested in knowing what those values are on other people people vehicles. It is perhaps possible that the value displayed is in fact a constant and not used by the autobox when mated with this engine ECU.

I presume that the addaptive values were reset when the other ECU was fitted and if yes the EAT ECU stored new ones in the volatile memory which are the result of the comunication with the replacement ECM while driving, any misscomunication through the CAN should have triggered a "Engine data invalid" fault code IMO


too bad i dont have an auto cos i would have took those readings for you to compare and relax your mind in this management area cos i'm convinced that it's something mechanical.... though it's just my oppinion so keep up the deep investigation

HI Ceebrady,
Requested Torque on my Nanocom is a constant 99% as well. In fact, all the input settings for the Auto ECU remain constant while I am driving so I suspect there is a small flaw in the system.

In any case your values are not wrong.

Hi and thank you to everyone Who has contributed to this topic.

Miss you with my gearbox turned out to be a sticking pressure control solenoid valve, which I've freed by applying 12 V intermittently across the terminals at this you that control that valve. I subsequently been warned that this may have destroyed the solenoid but I'm sure that I haven't as I only gave very short pulses for a short period of time and I could still hear it operating at the end of the test and the resistance of the solenoid remained 7.5 ohms.

This in spite of the local gearbox guy having replaced the valve body...

Gearbox now runs well, shifts are gentle in normal driving and crisp under acceleration.

Many thanks to everyone again.

Regards

Can I ask how you diagnosed that problem?

Came to thinking that it was to do with the pressure control because the shifts were harsh in the downshift at the time when you slowing down to stop, as well during upshift it was still reasonably harsh despite the engine ECU and auto ECU talk to each other during the upshift and torque from the engine lowered for the duration of the up shift driven upshift. Since the Nanocom only displays the value of its output for the pressure control value as there is no sensor to read the pressure with in the box it led me to believe that this may not be reflecting the true value of the pressure.
Prior to manually energising the pressure control valve solenoid (which I did primarily to hear operate) I did attempt to isolate the pin that provides the ground for the solenoid so that this valve would not open, this however threw a fault in the automatic ECU.
Does my method of diagnosis seem any more clear with this explanation?