Transmission serviced thump fixed

[Unique X5]

I recently bought a 2005 turbo diesel and when braking to a stop at the traffic lights it would thump in the rear just prior to stopping. I thought it was possibly the rear brakes grabbing and or worn cradle bushes. We checked the car out and nothing worn. The car has done 172,000 k's and the previous owner was towing two horses, pretty heavy things and in summer here in Sydney Australia.

The transmission was another candidate as it has never been serviced, which BMW state you don't need to, which I think is wrong. We did a service, new recommended Liquid Molly fluid and filter and seal change. No surprise the fluid came out quite dirty. Guess what, the thump went away as the tranny wasn't holding gears. It drives much nicer. I know someone with same year model with 4.4 V8 did same with the same improvement.