Hey guys, I have just been through the ringer on all this with my wife's car. I am sharing my experience in the hopes that it will help someone else.
My wife's BMW 2005 BMW 530i started exhibiting driving issues after we bought it. When coming to a stop it would bump pretty hard like someone was rear-ending us. In addition, it started throwing 4F85 codes.
We took it to BMW who told us we needed to swap out the tranny with a rebuilt one. My warranty company was not down with that and they had me take it to a transmission rebuilder. I took it to Eagle Transmission on Inwood in Dallas, Texas. Doug Brice is the owner and he is one of the best. Initially he rebuilt the transmission and found out why there was such a severe bump. Apparently there is some slack in the clutches that needs to be tightened up.
Once the car was back together, they test drove it and found the 4f85 code came back. We were both scratching our heads on this one because searching the forums and internet did not give us much. So he put a call into ZF, the manufacturer of the transmission and waited. Surprisingly a tranny rebuilder from ZF called back. He told him that 4F85 is not electrical, but mechanical. The bushing for the input shaft wears out of spec and then you start getting that code. You can't buy just the bushing, you need to purchase the shaft for about $500. It is not something you can just eyeball on the bushing, you need to measure it and check it against the limits of the allowable clearance.
He ordered a new input shaft and put it in, he said it was much tighter than the old part. We have had the car back a few days and I have to say, it is great. He took out the slop in the downshift and take offs, and we have not got the code again. If anyone is having this trouble, it is with the ZF ZFLS6HP19 transmission and he can take care of you. Keep in mind, this transmission is not just in the BMW 530i, but other BMWs as well. This problem seems to be quite a money maker for BMW and ZF. The bushing appears to be under-supported and thus wears quickly causing this issue. It would be nice if they would come out with a decent fix, but apparently building a quality transmission is less important than building a money making transmission.
Again, contact Doug and he can help you out.
His number is
3317 Inwood Rd
Dallas, TX 75235