Arto · Dec 14, 2022

Hi, can anybody help.

If i drive transmission hot enough, and after that when i slow speed down for example to stop at traffic lights, the car jerks before stopping (i think - when first gear goes in) the instrument panel display shows text "transmission fail limited gears in use" and after that only gears 1-3 are used.

When i turn off the car's power and restart the car, the transmission works until you have to stop the car again.

It don´t do that if i drive example only half an hour.

The car is Range Rover 3.6TD V8 Vogue Year 2008 type L322, i assume that the gearbox is the type ZF 6HP26.

What´s the reason?

Arto from Finland

PS. Sorry for any grammar mistakes as English is not my native language

Mark Piercy · Dec 14, 2022

Arto said:
Hi, can anybody help.

If i drive transmission hot enough, and after that when i slow speed down for example to stop at traffic lights, the car jerks before stopping (i think - when first gear goes in) the instrument panel display shows text "transmission fail limited gears in use" and after that only gears 1-3 are used.

When i turn off the car's power and restart the car, the transmission works until you have to stop the car again.

It don´t do that if i drive example only half an hour.

The car is Range Rover 3.6TD V8 Vogue Year 2008 type L322, i assume that the gearbox is the type ZF 6HP26.

What´s the reason?

Arto from Finland

PS. Sorry for any grammar mistakes as English is not my native language

Hi there, no apologies needed. I would have it checked before spending any money. There could be a number of things wrong...

Datatek · Dec 14, 2022

Arto said:
Hi, can anybody help.

If i drive transmission hot enough, and after that when i slow speed down for example to stop at traffic lights, the car jerks before stopping (i think - when first gear goes in) the instrument panel display shows text "transmission fail limited gears in use" and after that only gears 1-3 are used.

When i turn off the car's power and restart the car, the transmission works until you have to stop the car again.

It don´t do that if i drive example only half an hour.

The car is Range Rover 3.6TD V8 Vogue Year 2008 type L322, i assume that the gearbox is the type ZF 6HP26.

What´s the reason?

Arto from Finland
PS. Sorry for any grammar mistakes as English is not my native language

Oil and filter change for the gearbox would be my first step. Check for metallic particles in the sump and around the magnetic plug.

Bemble · Dec 14, 2022

Some of your symptoms align with a worn rear stator bush e.g. only gears 1-3 available, worse when hot:
https://www.landyzone.co.uk/land-rover/help-please-gearbox-issue.330768/#post-4269229
However, this issue usually manifests itself during acceleration, where the transmission refuses to upshift into 4th, 5th or 6th and just hangs on to 3rd gear.
In your case the problem seems to arise when you're slowing down. Solenoids are also a big problem with the 6HP26X, so that's another possibility.
I think you really need to get the codes read.
Phil

Arto · Dec 14, 2022

Okey
I have reserved oil and filter change and code reading from nearest Bosch Car Service garage, but first time was 2.1.2023.
So let's see if those help first.
Arto

A1EK · Dec 21, 2022

I've had this same issue, and as others have said it sounds like the solenoids! The majority of the car is BMW with the exception of the crap gearbox made by GM. The good news is you can get the gearbox overhauled, bad news is it will cost as much as the car. I just had mine done and it was £3500 Good luck

Bemble · Dec 21, 2022

A1EK said:
The majority of the car is BMW with the exception of the crap gearbox made by GM

Arto has a 2008 model, so he’s lucky enough to have the ZF 6HP26X transmission

Engines%20amp%20Transmissions_zpsvfxhhw95.jpg

Phil

Datatek · Dec 21, 2022

A1EK said:
I've had this same issue, and as others have said it sounds like the solenoids! The majority of the car is BMW with the exception of the crap gearbox made by GM. The good news is you can get the gearbox overhauled, bad news is it will cost as much as the car. I just had mine done and it was £3500 Good luck

Hope you specified the Sonnax valve block.

Arto · Dec 21, 2022

Yes I think its ZF 6HP26. Datatek - What did you mean with "Hope you specified the Sonnax valve block" i didn`t understand.
To A1EK - In Finland such a 2008 RR TDV8, which has been driven for less than 200K, costs around €15,000, so a possible repair would hopefully cost less.
Arto

Datatek · Dec 21, 2022

Arto said:
Yes I think its ZF 6HP26. Datatek - What did you mean with "Hope you specified the Sonnax valve block" i didn`t understand.
To A1EK - In Finland such a 2008 RR TDV8, which has been driven for less than 200K, costs around €15,000, so a possible repair would hopefully cost less.
Arto

Ah, the Sonnax only applies to the earlier GM box fitted to the L322.

Arto · Jan 6, 2023

The oil and filter change has now been done and the fault codes have been read.
Oil was clear and there were no metallic particles around the magnetic plug's.
The car still jerks when stopping, but not so bad anymore and shifting is also smoother.
2 fault codes were found, P0730 Transmission ratio malfunction and P0731 Transmission ratio, 1 gear, malfunction.
There has not been a single transmission failure yet while driving after the oil change.
Can anyone advise on what to do next based on those fault codes or should I just wait to see what happens.
Arto

Datatek · Jan 6, 2023

Arto said:
The oil and filter change has now been done and the fault codes have been read.
Oil was clear and there were no metallic particles around the magnetic plug's.
The car still jerks when stopping, but not so bad anymore and shifting is also smoother.
2 fault codes were found, P0730 Transmission ratio malfunction and P0731 Transmission ratio, 1 gear, malfunction.
There has not been a single transmission failure yet while driving after the oil change.
Can anyone advise on what to do next based on those fault codes or should I just wait to see what happens.
Arto

If it were me, I would wait and see.

Bemble · Jan 6, 2023

The code is telling us that a clutch is slipping in 1st gear.
The A-clutch and the D-brake are the friction elements used for 1st gear.
The A-clutch is also used in 2nd, 3rd & 4th gears.
The D-brake is also used in Reverse.
Do you have an issue with Reverse, at all?

So, unless you actually come to a halt in Drive, causing the controller to select 1st gear, the car will drive around happily all day? In Manual mode I believe you can select either 1st, 2nd or 3rd gears to drive off from stationary. Presumably, as a temporary measure, you could drive around in Manual mode and stop/set off in 2nd gear to avoid the failsafe message?

6HP26%20solenoid%20control_zpscol3xls7.jpg

Phil

Arto · Jan 7, 2023

Hi Phil
Thank you for a really knowledgeable answer.
Yes, if I don't stop I can ride as long as I want without a fault. When I next time drive a long distance, when the box warms up enough and the fault appears, I have to try the manual mode. I haven't tried it, so that's what I have to do.
However, it feels that way as if the first gear doesn't slip, it just engages a little late and jerks when engaged.

Arto · Jan 7, 2023

And this was forgotten from the previous one:
There are no problems using Reverse at all.
Arto

Arto · Jan 17, 2023

Oops! it did it again (almost like Britney Spears sang) once. However, I have driven very little and relatively short distances.
I didn't notice the error message, but when I continued driving after the stop, only gears 1-3 were in use. When i noticed this i pulled over to the next bus stop and turned off the power and restarted the car. After that, the gearbox worked normally again. On the way home I used Phil's suggested method and switched to manual and from there to 2nd gear and it worked well with 2nd gear staying on even when stopped.
However, there is something wrong with the gearbox, but what?.
From other faults, so much so that when I bought the car, the navigator and the CD changer did not work. I located the faults in the GPS antenna and the mechanics of the CD changer. I ordered a used antenna from eBay (€90 from Spain) and a CD changer (€145 from UK). Now they are in place and luckily the systems work.
Arto

Bemble · Jan 18, 2023

So the fault code says either your A-clutch or D-brake is slipping in 1st gear, yet the other gears which use the same clutch & brake are working fine. Certainly a tricky one to diagnose. The 6HP26 has around half-a-dozen common faults, but this isn’t one of them. I think I’d probably remove the Mechatronic unit next, check the condition of the bridge seal and the 4 jump tubes, and then test each of the clutch ports with air pressure to check for internal leaks.

6HP26%20pressure%20test%20points_zps8kfcsnvx.jpg

If you have diagnostic kit capable of measuring and recording live data (e.g. IIDTool) then you could try recording what’s happening inside your transmission when you come to a halt . The problem is that the data acquisition will be at around 16Hz per live value (e.g. 4Hz for 4 live values) and this may not be quick enough as the downsequencing happens really quickly as you come to a halt.

Phil

Arto · Jan 18, 2023

Hi Phil
So, when Reverse works ok the fault can’t be D-brake witch both are using. And when clutch A is also in use with gears 2-4 and they work, it can’t be faulty. My question is that what tells A-clutch and D-brake to work when the car’s speed is slowing near zero.
Arto

Bemble · Jan 18, 2023

Arto said:
So, when Reverse works ok the fault can’t be D-brake witch both are using. And when clutch A is also in use with gears 2-4 and they work, it can’t be faulty

Exactly

Arto said:
My question is that what tells A-clutch and D-brake to work when the car’s speed is slowing near zero

The transmission ECU/controller (which is part of the Mechatronic unit) has a map in its software which tells the transmission to downshift into 1st as the vehicle comes to rest.

The Mechatronic has its own input and output speed sensors to tell it when to do this.

To achieve the gear change it sends current to the relevant solenoids to apply the hydraulic pressure to activate the clutches (in the case of a yellow-capped solenoid) or removes current from a solenoid to apply hydraulic pressure to activate the clutches (in the case of a blue-capped solenoid). So in 1st gear the EDS1 (yellow) solenoid is activated to engage the A-clutch and the EDS4 (blue) solenoid is deactivated to engage the D-brake.

The solenoids have a poor reputation for durability and are a very well-known cause of issues with the 6HP26 but, if it was a solenoid problem, why would the same clutches work fine in some gears and not others?

6HP26%20Solenoid%20Set%201068_298_044_zpsg12b25qt.jpg

Puzzling…

Phil

Arto · Jan 18, 2023

Wow, now I got maybe too much information about the operation of this automatic transmission.
And a little more - why does going into first gear work relatively well with a cold box and get worse as the box warms up.
I was thinking that could the operation of some solenoid be temperature sensitive.
And which one would it be when the change is more delayed and the jerking gets worse when it warms up.
Other shifts go as they should without temperature dependence, which would indicate that the fault is not caused by the solenoids.
And lastly which frees the action at start up, releasing all gears for use, would this indicate that some information coming to the ECU is temperature sensitive - for example, speed.
Arto

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