04-06 E60?
If so then it's like mine (120k km). Just got it back from M-Scope in Batu Caves.
Symptoms:
1) Kena error, transmission failure while going down steep hill when car downshifted. Upon restart, it disappears.
2) Also, slippage when shifting from 4-5 and 5-6, feels like the car shifts into neutral for a couple of secs and the revs spike, before it engages next gear.
3) Rough 1-2-3 downshifts, a bit of transmission slam as car approaches a complete stop.
4) Loss of power. 530i, felt more powerful before first tranny fluid change at 70k.
5) While stationary, the car will jerk forwards when gearshift is moved from D > M > M1 > M2 and back to M1. Very apparent and sharp jerk. Quill guys says very abnormal.
Quill themselves recommended gearbox replacement. RM25k+. Hah.
Tan from M-Scope explain to me that the ZF 6HP on mine is earlier version, so like many others (on this board) there are valve/solenoid issues.
He ran it thru his ZF diag, and it showed 250+ instances of clutch slip from 4-5 and 5-6 from 70k km, which was about the time I first felt it and sent it in for tranny oil change, to 120k km.
He took apart the mechatronics, replaced the worn valves and springs, solenoids and solenoid caps. Took 2 days, cost 5.5k.
Apparently he modded it with slightly bigger springs to provide more resistance, and the green solenoids were replaced with the newer upgraded blue ones and he changed out the yellow ones. Green ones apparently got issues. He said the problems should not recur with these new parts. 6 month warranty, and I have to take car back after 3 weeks for them to check up on it. It'll run rough for these 3 weeks but after that, it should be smooth as baby's butt, hopefully. This guy seems to know his gearboxes, and I think he's done more than a few BMWCM cars.