L322 2006 automatic gearbox thumps down gear when cold

Hi, i have a 2006 l322 td6. Car drives great when warm but thumps down gear when cold. I took it to a reputable range rover gearbox specialist. He said the gearbox was faulty. Had a full rebuild done with torque converter. This hasn't changed a thing, i't been back more times than i care to mention. It's also had a transfer box. Again no change. No faults come up at all. As i said drives great when warm after about 5 minutes. Any help would be greatly appreciated.

Ouch! Has he offered you your money back as his expertise did not fix your problem?
You need @Bemble to go through it with you he's the auto-box god on here.

Could be a software related issue.

DanClarke said:

Ouch! Has he offered you your money back as his expertise did not fix your problem?
You need @Bemble to go through it with you he's the auto-box god on here.

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No, it's been back 6 times and all he wants to do is change bits like valve hosing and charge more.

Henry_b said:

Could be a software related issue.

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Had the ECU changed.

m2006d said:

Had the ECU changed.

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That doesn't mean it has the latest software.

Does the software time out. The ecu had a reset done when it was fitted and this made no difference at all. I would have thought it would have been ok with a reset as that's what they are first sold with.

m2006d said:

Does the software time out. The ecu had a reset done when it was fitted and this made no difference at all. I would have thought it would have been ok with a reset as that's what they are first sold with.

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A reset only restarts the software, it does not update it to the latest version which would have been an after market update