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Alfabeat
Member Since: 16 Nov 2022
Location: Herefordshire
Posts: 9
  
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| Gearbox issue Disco 4 TDV6 Automatic (59 plate) |
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Hello. I'm new to this forum, and am hoping someone can offer some advice....
The vehicle has 140k on it. Gearbox oil has recently been replaced by a LR Indy.
The problem, which was present prior to the gearbox flush/oil replacement, and is still present is that on a longish journey, towing the loaded horsebox, usually, on a hill, the gearbox slips into Neutral (although the gear lever remains in "D").
Stopping the vehicle, putting it into "P" and turning off the engine and restarting, sorts it.
Always happens under load and when well and truly warmed up!
Otherwise, it shifts perfectly and behaves itself. If not towing, it hasn't occurred.
On a few occasions, when parking up and putting the box into "P", the "P" flashes on the dashboard. Not sure if this is relevant or not?
I have booked the vehicle back into the Indy to take another look, but I'm just wanting to gather some independent advice, before being told I need a new transmission or something.....!
I have had this vehicle for 7 years, and had the normal issues (manifolds, water connector, bushes etc), but never any issues with the transmission.
Thank you
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 16th Nov 2022 11:13 am |
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NJSS
Member Since: 06 May 2009
Location: Catherington, Hampshire.
Posts: 10808
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Welcome Alfabeat
Sorry I can't help with the problem - hope it's easily & cheaply resolved though.
NJSS
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| 16th Nov 2022 11:19 am |
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disco chris
Member Since: 25 Apr 2022
Location: London
Posts: 288
 
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I don't think this will be the problem, otherwise the gear lever would probably also go into neutral when the gearbox does, but worth a look:
https://www.disco3.co.uk/forum/autobox-gea...r+selector
If it doesn't sound like your issue then apologies, I can't help. Hopefully someone will come along soon who can suggest something else...
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| 16th Nov 2022 11:35 am |
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Trailered Movements
Member Since: 16 Jan 2020
Location: East/West Sussex Coast Borders
Posts: 1200
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Within the gearbox is a valve and electronics unit, called a 'megatronic unit'.
The gear lever moves a plastic slider along a circuit board which is encased in silicone.
Mine failed when it got hot, although it was to do with the car thinking it was in 'P' when it wasn't, and vice versa.
There is no repair for this, some will say fit another gearbox, however I fitted a secondhand megatronic unit from a similar year car (actually an RRS) without any issues.
A replacement new unit is just under a £1,000 from ZF, and the same unit from LR is around £1,600. Everyone will tell you it has to be coded from the factory which it is, but, if you can fit a secondhand gearbox, why not the only part that has to be programmed, ie., the megatronic unit. It worked for me.
I had to take my car to a ZF gearbox specialist to have the gearbox diagnose the fault, but it was £60 well spent.
Dave 2011 Discovery 4 Commercial SDV6 (Gone)
2010 RRS TDV8 (Gone)
1980 OBLIC 4.0ltr Range Rover (went a long time ago)
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| 16th Nov 2022 11:41 am |
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Alfabeat
Member Since: 16 Nov 2022
Location: Herefordshire
Posts: 9
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disco chris wrote:I don't think this will be the problem, otherwise the gear lever would probably also go into neutral when the gearbox does, but worth a look:
https://www.disco3.co.uk/forum/autobox-gea...r+selector
If it doesn't sound like your issue then apologies, I can't help. Hopefully someone will come along soon who can suggest something else...
Thanks! I'm pretty sure they cleaned up this lever/cable when it was in for the oil change. But will check.
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| 16th Nov 2022 12:12 pm |
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Alfabeat
Member Since: 16 Nov 2022
Location: Herefordshire
Posts: 9
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Trailered Movements wrote:Within the gearbox is a valve and electronics unit, called a 'megatronic unit'.
The gear lever moves a plastic slider along a circuit board which is encased in silicone.
Mine failed when it got hot, although it was to do with the car thinking it was in 'P' when it wasn't, and vice versa.
There is no repair for this, some will say fit another gearbox, however I fitted a secondhand megatronic unit from a similar year car (actually an RRS) without any issues.
A replacement new unit is just under a £1,000 from ZF, and the same unit from LR is around £1,600. Everyone will tell you it has to be coded from the factory which it is, but, if you can fit a secondhand gearbox, why not the only part that has to be programmed, ie., the megatronic unit. It worked for me.
I had to take my car to a ZF gearbox specialist to have the gearbox diagnose the fault, but it was £60 well spent.
Dave
That's interesting. It does seem to be more of an "electrical / sensor" issue than a mechanical issue if that makes sense. Which specialist did you use for the diagnosis?
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| 16th Nov 2022 12:13 pm |
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Trailered Movements
Member Since: 16 Jan 2020
Location: East/West Sussex Coast Borders
Posts: 1200
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A local one to me in Sussex, but a search of automatic specialists in your area will produce someone who is a ZF agent, and you just need to ask them if they have ZF diagnostics equipment.
Dave 2011 Discovery 4 Commercial SDV6 (Gone)
2010 RRS TDV8 (Gone)
1980 OBLIC 4.0ltr Range Rover (went a long time ago)
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| 16th Nov 2022 12:41 pm |
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Alfabeat
Member Since: 16 Nov 2022
Location: Herefordshire
Posts: 9
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I took it back to the Indy who had flushed the box and changed the oil. They were convinced it is a simple case of adjusting the cable, which they have done.
We shall see! Fingers crossed. Thanks to everyone who gave me some advice.
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| 19th Nov 2022 5:35 am |
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Alfabeat
Member Since: 16 Nov 2022
Location: Herefordshire
Posts: 9
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Well, it has done it again, with a loaded horse box. Next stop a ZF transmission specialist... 
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| 20th Nov 2022 2:58 pm |
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Lee Trinder
Member Since: 12 Aug 2018
Location: Henley in arden
Posts: 516
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Maybe reset gearbox adaptions?
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| 20th Nov 2022 4:25 pm |
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Alfabeat
Member Since: 16 Nov 2022
Location: Herefordshire
Posts: 9
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I'm sure they reset everything when they did the oil change.
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| 20th Nov 2022 4:34 pm |
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motorworks
Member Since: 14 Nov 2019
Location: Usk
Posts: 412
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Circumstances that you describe, are (I believe) maximum load on the transmission and minimum viscosity of the gearbox oil due to high temperature. Gearchanges are achieved by a valve block applying
hydraulic pressure to open and close servos. Sudden loss of pressure will release a servo and clutch pack resulting in "neutral" drive.
The ECU may be faulty, but the extreme conditions when the failure happens suggest early signs of a mechanical problem to me. If the gearbox is original, 140k miles would support my theory, and oil change would not fix it.
Is the D4 2.7 or 3.0? Chris
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| 20th Nov 2022 9:18 pm |
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Alfabeat
Member Since: 16 Nov 2022
Location: Herefordshire
Posts: 9
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Hi... It is a 3.0.
If it was valve / solenoid failure, which is normally the best route forwards?
Rebuild box
Replace box with new
Replace valve unit
Replace with 2nd hand / refurbished box
Thanks for taking the time to comment.
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| 20th Nov 2022 11:50 pm |
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Flatlander
Member Since: 20 Jul 2015
Location: Here
Posts: 575
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Assuming there are no overheat messages on the dash, then the most likely cause is a mechatronic / solenoid fault, if there are / were overheat messages, then that would suggest clutch pack wear - which would require transmission overhaul to resolve.
All of the above is based upon the assumption that the transmission oil is correct type and fill quantity with no friction modifiers added - which can skew diagnostics.
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| 21st Nov 2022 12:12 am |
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Alfabeat
Member Since: 16 Nov 2022
Location: Herefordshire
Posts: 9
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Thank you all.
Car is booked into Bristol Transmissions in early January for diagnosis....and then hopefully repair. I will update this then for completeness and it may help someone else in the future.
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| 21st Nov 2022 11:23 am |
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