Sounds like it needs a proper overhaul this time. There shold be plenty of shops who can rebuild the ZF tranny for a lot less than a replacement. You may still be looking at $3k though, depending upon what has worn out. The labour charge is the killer as it takes about 17 hours to remove, strip, rebuild and refit the box. Parts will be around $1k for the OEM service kits - clutch packs, oil filter, gaskets etc.

I had a catastrophic premature failure 18 months ago and with a new Mechatronics Unit added as well the total was just over £3,200. BMW price was £10,000!! You should not need that module though unless something really nasty has happened. In my case part of the torque converter fractured and bits of metal were spread via the now also damaged and then broken oil pump (jammed) into the whole system causing consequential failures in two clutches and a brake pack when the hydraulic pressure suddenly dropped.

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