E34 1996, M50. I encounter the same problem years back, GB problem, wasted $ on changing GB fluid and filter but problem remain, later sent for complete overhaul as advise at a famous GB specialist, can't say here or he might sue me, spent RM 5k, after the repair my car was in / out of workshop countless time, problem like GB warning light, jerking but was finally settled, he gv me 2 years warranty to show he is confidence with his product, BTW the specialist work suck and my newly overhaul GB fail again after 60k km and out of warranty. I had enough, this time i converted and changed the GM GB to jetco GB, spent RM5k also but i am happy with it, any future repair will be very cheap as jetco GB is very much cheaper.