E39 530D Transmission problem

[davidvh2]

Hi Folks.
I asked the forum a long time ago about the following problem but alas, whilst many read my message, nobody could help but I'm hoping somebody may this time.

During the 6 years I've had this car, the gearbox has been completely overhauled once (at around 100,000 Kms) & now the same problem has been with me for some months. I just don't want nor feel that another expensive overhaul should be required at around 200,000 Kms although the car was changing up & down properly (including changing down during a decent) for many months after the overhaul. The symptoms are as follows:-

First of all the car drives perfectly & changes gears on time & smoothly. The only time one is aware that something is not correct, is on the over run particularly when going down a long hill. It may OR MAY NOT drop down a gear. Sometimes it will drop down a gear (so providing desirable engine braking) & I'll see the revs rise. Moments after that, the revs will drop to idle & I can feel the total loss of engine braking meaning that I'm then totally reliant on the service brakes. At other times it'll stay in the lower gear all the way down the hill which really makes this a fine car to drive.

Living in a hilly part of Spain, not having a reliable engine brake is not desirable as you'll no doubt appreciate. Anyone living & driving in predominately flat areas probably wouldn't notice this problem. Any advice most welcome but I have a feeling (maybe quite wrong) that this could be as a result of one of more of the solenoid valves on the GM gearbox not working or sealing properly. Any tips will be most appreciated.