The brief
This 730i came in for a total gearbox overhaul, the point an automatic box reaches when years on tired fluid have worn the internals enough that shifts have gone harsh, slow or flarey and a fluid change alone won't bring it back. The automatic transmission fluid lubricates, cools, and does the hydraulic work of every shift, and it degrades under heat and friction. Left too long it stops protecting the clutch packs and the valve body, so the wear builds, and once it's at that stage the box has to come out, get stripped, cleaned thoroughly, and have the worn parts renewed before it's reassembled, that's an overhaul, and doing it properly means a genuine repair kit and a spotless rebuild.
The diagnosis
A road test and the condition of the fluid confirmed the box needed an overhaul, and a 360-degree undercarriage check went over the car at the same time. With the gearbox out and stripped, the worn clutch components, seals and valve body parts were the cause of the rough shifting, the result of the fluid having gone too long. That's a full gearbox overhaul, every part cleaned and the worn internals renewed from the repair kit, plus fresh fluid and a new filter, rather than a fluid change that wouldn't touch the worn hardware.
The work
The gearbox was systematically dismantled from the car and stripped to its components, every part cleaned until the interior was spotless, and the worn clutch parts, seals and valve body pistons renewed from the genuine BMW repair and packing kit. The box was reassembled with care, refitted to the car, and filled with the correct BMW fluid to the right level at the right temperature, the way it wants it. The adaptations were reset so it relearns its shift points on fresh fluid and clean hardware. A road test confirmed smooth, prompt shifts up and down, no flare, no jolt, and the box behaving like it should, all turned around in a day.
The outcome
Smooth, prompt shifts through the whole range, no jolt between gears, no flare, fresh fluid and a clean filter, and a gearbox that drives like it's been looked after, done in a day. The 730i went home with the box overhauled and shifting properly. Neglected fluid is what gets a gearbox into this state, so keeping the fluid changed on schedule from here is far cheaper than another overhaul.
