Auto gearbox woes

Sorry folks this might be a long one so grab a beer or tea!

I have a discovery2 from 2001 fitted with a td5 engine and 4hp-22 auto box.
When purchased all was good for a few months when one of the pipes leading to the gearbox oil cooler came adrift leading to a catastrophic loss of fluid. Pipe replace an box refilled all was good again for a while.
The box then started to mess about and eventually it wouldn’t allow the car to move except in low range. A replacement box was sourced second hand and fitted and movement was restored. The original torque converter was reused.
The problem now is the torque converter will only lock up occasionally and mostly when cold. In an effort to resolve this we have…
Replaced the oil cooler and pipes.
Flushed the gearbox on countless occasions.
Replaced the transmission oil temperature switch.
Fitted a refurbished xyz switch.
Most recently did a modification which bypasses the ecu control of the lock up and allows the driver to lock it using a switch.

It will still only lock when cold, when warm if you switch it it doesn’t engage the lock up but it does produce a strange noise from somewhere within the dash.

We are literally tearing out hair out at this stage!

Could any of you offer any suggestions as to what the next move should be?
Could it be a faulty gearbox or torque converter or is it likely to be external to the gearbox?

If your still with me thanks for sticking around to read my post!

Eggusone said:

Most recently did a modification which bypasses the ecu control of the lock up and allows the driver to lock it using a switch.

It will still only lock when cold, when warm if you switch it it doesn’t engage the lock up but it does produce a strange noise from somewhere within the dash.

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Hi, the next move should be to find somebody with nanocom and run live output test on the lock-up solenoid cos seems very that the problem is on that circuit albeit the M + S warnings should come on in this case and you didnt mention anything about that.... there is nothing within the dash connected to the valve block so the noise might come from the solenoid but somehow "reflected" into the dash

BTW did you ever see the M + S warnings since this saga has begun? ... if yes the first move should be to read the stored fault code, you cant fix such issue without properly diagnosing it first

sierrafery said:

Hi, the next move should be to find somebody with nanocom and run live output test on the lock-up solenoid cos seems very that the problem is on that circuit albeit the M + S warnings should come on in this case and you didnt mention anything about that.... there is nothing within the dash connected to the valve block so the noise might come from the solenoid but somehow "reflected" into the dash

BTW did you ever see the M + S warnings since this saga has begun? ... if yes the first move should be to read the stored fault code, you cant fix such issue without properly diagnosing it first

Click to expand...

Hi , thanks for the reply. No there has never been any warning lights on . According to the nano com everything is working as it should with all valves opening and closing at appropriate times although I’m new to nano com I think I’m correct in how I’m using it.

Eggusone said:

According to the nano com everything is working as it should with all valves opening and closing at appropriate times

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In this case the probem is probably mechanical and that's beyond my knowledge, run a stall test on it eventually