Problems with automatic transmission during BMW braking – how to fix it?

BMW driver question

I bought a car 5 years ago with a 5HP24 automatic transmission and a replaced timing gear (Vanos not repaired). Since the beginning of use I have this effect: when braking the car, for example, at traffic lights, it strongly “drops” the last gear. There is a throttling effect, almost the impact of a sudden change from second to first gear.

This causes the revs to drop below 4000 RPM and rapidly pick up to the normal 6000 RPM. The computer shows no errors. Dynamic and static oil changes have not helped. I tried using reputable oils as well as replacements – FEBI, Ravenol. I replaced the throttle valve with the one offered by Pierburg. Bosch flowmeter, as well as the fumes, probes and plugs. The problem still occurs. Both on gasoline and on LPG.

The effect is minimized by switching on, for example, the air conditioning (load), which forces the revs up. Other than that, the transmission has so far changed gears correctly, lightly, without noise. However, the above-mentioned whipping during braking severely stresses the reducer and other components. Please advise if this is a failure of the transmission, valve train or Vanos? Where to look for a solution to the problem? Unfortunately, the lack of knowledge in workshops in my place of residence.

The question was about BMW X5 E53, but it may also occur in other models.

Response from BM Cars service

The described gear reduction symptoms in the 5HP24 automatic transmission should not occur. In a functioning transmission, gear shifting or gear reduction is not noticeable. In high-mileage transmissions, a gear change may be felt gently, but it should never be associated with jerking or banging or other noises.

Repairing the fault on the basis of accidental or default replacement of components (replacement of the throttle, flow meter) makes no sense and should not be done. Automatic transmissions rarely show errors in computer diagnostics despite their clearly bad operation. An additional element important in their operation is the quality and quantity of oil. The only reliable oil is the original oil from ZF.

It is also important to properly fill the box during an oil change. Lack of the right amount of oil can also result in a slight jerking during gear changes.

We suggest taking the following steps:

1. Check the quantity and quality of the oil in the transmission. If the quality and quantity are wrong, proceed to the next step.
2. Disassembly of the gearbox and verification of the condition of the gearbox after disassembly.
3. Replacement or reconditioning of the torque clutch.
4. Reassembly of the transmission and filling with oil.
5. Deleting the adaptation in the box and performing re-adaptation.

After performing the above steps, the malfunction should be resolved.

If the nearest service center cannot undertake such a repair, please consider transporting the car on a trailer to BM Cars.

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