L322 ZF8HP70 gearbox problem

kermit_rr · 2024-10-30T20:42:31+0000

Graculus said:
Don't do that! The only time that should be done is if a software change requires it or solenoids have been replaced, doing so on a 'box that has had no work done can lead to some pretty bad shifts, some 'boxes never achieve their previously 'acceptable but could be better' shift behaviour.

I'll not do that then! Heard similar elsewhere too

Graculus · 2024-10-30T20:52:27+0000

kermit_rr said:
I didn't see a live data selection called output speed sensor but saw a few others.
Transmission output shaft speed was interesting, it was at zero apart from a spike when starting and a spike when stopping.
There was transfer box motion sensor voltage which went from low to high, the switch happened before i came to a stop

This sounds like it may be relevant to your issue:-

A new feature of the 8 speed transmission is decoupling of the transmission
when the vehicle is at a standstill. Normally the transmission remains in gear
with the torque converter slipping and the vehicle is prevented from moving
by applying the brake. The new system disengages one of the transmission
clutches and only a minimum rotating load remains

And

Speed Sensors

The turbine speed sensor and the output shaft speed sensor are Hall effect
type sensors located in the Mechatronic valve block and are not serviceable
items. The TCM monitors the signals from each sensor to determine the
input (turbine) speed and the output shaft speed.

The turbine speed is monitored by the TCM to calculate the slip of the

torque converter clutch and internal clutch slip. This signal allows the TCM
to accurately control the slip timing during shifts and adjust clutch
application or release pressure for overlap shift control.

The output shaft speed is monitored by theTCM and compared to engine
speed signals received on the CAN bus from the ECM. Using a comparison
of the two signals the TCM calculates the transmission slip ratio for
plausibility and maintains adaptive pressure control.

So the output speed sensor monitors and reports rpm, it's not an 'on-off' sensor, which yours seems to be behaving as. Unfortunately it's not a serviceable item from LR - but may be at a ZF service centre.
You may wish to have a proper diagnosis carried out rather than a virtual one if it involves spending what little cash the incumbent Gov't. leaves you with.

kermit_rr · 2024-10-30T20:56:34+0000

Graculus said:
This sounds like it may be relevant to your issue:-

And

So the output speed sensor monitors and reports rpm, it's not an 'on-off' sensor, which yours seems to be behaving as. Unfortunately it's not a serviceable item from LR - but may be at a ZF service centre.
You may wish to have a proper diagnosis carried out rather than a virtual one if it involves spending what little cash the incumbent Gov't. leaves you with.

Thanks. There's a 'gearbox specialist' near me, or do you mean an actual ZF centre?
These folks https://www.autolock-crewe.co.uk/

kermit_rr · 2024-10-30T20:59:23+0000

So if it's a bad sensor, it's located in the mechatrinic module.. that means a rebuilt unit from what I've read

Graculus · 2024-10-30T21:04:40+0000

You can change the Mech, I've done quite a few on various ZF 'boxes - even more on M-B & VWG transmissions... If the sensor is defective and it is replaceable seperately, then a ZF centre will be able to do it, your transmission specialist may be able to do it if ZF sell it as a spare component to third parties. I would advise getting a proper, physical diagnosis carried out to confirm this 'virtual diagnosis' before committing to any repair though.

kermit_rr · 2024-10-30T21:16:20+0000

Graculus said:
You can change the Mech, I've done quite a few on various ZF 'boxes - even more on M-B & VWG transmissions... If the sensor is defective and it is replaceable seperately, then a ZF centre will be able to do it, your transmission specialist may be able to do it if ZF sell it as a spare component to third parties. I would advise getting a proper, physical diagnosis carried out to confirm this 'virtual diagnosis' before committing to any repair though.

Found this place near me.. perhaps a good first contact
ZF Services UK, Wrexham
Redwither Road
Wrexham Industrial Estate
Wrexham LL13 9RD

Graculus · 2024-10-30T21:20:41+0000

They'll be able to give yes/no answers rather than the maybe/possibly you might get from a broad-range specialist.

Mark Piercy · 2024-10-31T05:29:30+0000

The box in the Chrysler/merc 300d? yep seen that one.

Graculus said:
You can change the Mech, I've done quite a few on various ZF 'boxes - even more on M-B & VWG transmissions...

Graculus · 2024-10-31T06:40:05+0000

Mark Piercy said:
The box in the Chrysler/merc 300d? yep seen that one.

No, much more recent vehicles than that! many still in manufacturers warranty....
When I was at VW, there was at least one vehicle a day in for a Mech. replacement, where I am now, we average two a month, again, not particularly old vehicles.

kermit_rr · 2024-10-31T07:05:02+0000

Yes I'll get it diagnosed properly, but if that's the issue, sounds like i should be getting a replacement mech unit, if i want it to last.. but not a cheap item

Mark Piercy · 2024-10-31T07:52:13+0000

Graculus said:
No, much more recent vehicles than that! many still in manufacturers warranty....
When I was at VW, there was at least one vehicle a day in for a Mech. replacement, where I am now, we average two a month, again, not particularly old vehicles.

I'd seen that, the vw/audi boxes had the filter gaskets for the solenoids breaking up and the gauze blocking the solenoid nose.

L322 ZF8HP70 gearbox problem

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