Having thought my issue was solved - it is back. To summarise I have an 05 4.2 S/C with low mileage. I have had an intermittent problem with the car making a low pitched humming sound at low speeds when going uphill for a while. Intermittently I also have a hard downshift from 2-1 - but I think that might be a different problem.

I had the transmission flushed and added lubefix but that has done nothing. Note the rev needle doesn't fluctuate at all when the sound is made and it happens regardless of the car being in automatic or semi automatic mode and there are no codes of any kind coming up on iid. Having searched exhaustively the closest case I can find to mine is a guy that reported the eventual cause of his problem as "valve block failure". Does anyone know how I can diagnose this? Should I just buy a new £300 valve block unit and see what happens? Why would a failing valve block cause this issue? Thanks

What makes you think it's the gearbox..? Pete

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2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-

Purely on the basis that this was the identified cause in the case that i can find that is closest to mine. Other than the gearbox I have checked for binding breaks , heat shields and the prop centre bearing - they all seem fine. In the absence of any error codes I am stumped. If it's not the box then what to try next? Diff? Transfer case?

Is the noise speed related, ie does it change with engine speed or vehicle speed..? Pete

__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-

It's definitely road speed - only happens below 15mph and never above

What happens if you knock it into neutral and glide..? Pete

__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-

I tried to do it but it is impossible - it only happens when going uphill at low speed - putting the car into neutral in those conditions and it just stops

Well I can't help with what that is but I am pretty sure it's not the gearbox, just doesn't sound like a gearbox issue if it is working fine...

Trying to find similar problems on line is near impossible due to the way everyone describes a noise...!!

I think you need a good inde to look at the car..

Dartford transmissions are supposed to know the gearboxes well, maybe a trip to them to either confirm or rule it out, certainly cheaper than just trying to guess and throwing bits at the problem...  Pete

__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-

From data kindly collected by forum members using the IIDTool it would appear that the torque converter lock-up clutch on 6HP26X transmissions fitted to the L322 isn’t applied (in controlled-slip mode) until the transmission is in 3rd gear – typically 24mph+ at light throttle.



The fact that you’ve added a friction modifier to the fluid, and this has had no effect, also indicates that it’s unlikely to be the LUC causing the vibration. However, if you have access to diagnostic kit that can measure & record the transmission parameters, we could certainly analyse the data to see if it corresponds with what you’re experiencing?

Phil

You could also send your Mechatronic unit up to Pete Stirrup at Valve Bodies UK (https://www.valvebodyuk.co.uk/) to have it tested on one of their Hydra-Test machines, to see if it gets a clean bill of health.



Phil

Many thanks Haylands & Phill - I think I need to read some live values/do some data logging to try and work out what's going on