At post 17 by Jordo I was thinking exactly what he said at post 19 , pressure issues so Jordo here is some candy for you to get your teeth into , enjoy .
My visit at ZF Dortmund for Gearbox maintenance.(very, very long!) HUGH RESULT!!
Servicing The e38 Automatic Transmission
http://e38.org/transfund1.pdf
Transmission issues cured by new voltage regulator/transmission cooler? Has
Troublesshooting