The ZF in my 2800 makes a bit of rumble when sitting at idle with the clutch out, so I've guessed that the input shaft bearings are going bad. The needle bearings are NLA while the large ball bearings are cheap and easily available. My engineering friend tells me that the needle bearings should be more robust than the ball bearing because of the larger area to distribute the load so I was going to change the ball bearings out to see if that fixed my issue. I even bought the correct puller for the ball bearings but then I found a rebuilt Getrag 265/6 on ebay for $1200 so I scooped it up and will be installing it instead.
Rebuilt 4 speed ZF transmissions are still available from BMW. Dealers that sell mail order want about $3k, your local dealer might want more. I've heard that parts to rebuild the Getrag 265 are very scarce now.
Ian