Transmission bearings and shimming

[pallum]

Alright, decided now was a good time to break everything open and take care of this input shaft nonsense hopefully for good. Opened transmission, pulled out input shaft and am now into the part I've been dreading.

So I opted to just buy a used complete input shaft with good splines, but after comparing the new shaft to my current one, the tapered roller bearings have me concerned. The current shaft's bearings aren't quite "tight," but are certainly not as "jiggly" as the new shaft's bearings. They're loose to the point that shaking the shaft makes it sound like a rattle. Is that "jiggle" any sign of bearing wear? There's no pitting or other surface defects, just the jiggle. If that slack will be taken up by a proper shim, I may just save myself the $80 for new bearings (unless someone knows a cheaper option available in the US).

[Rick G]

Remove the baering on the front of the shaft and under there is a shim/s which adjust the preload on the taper roller bearings.  Shim it up till you can turn it easily with your fore finger and thumb but so that when you give it a quick spin it wont keep spinning it stops as soon as the fingers let go.  Do it without any other shafts in the box, no gears.
 If you are not sure get a pro to do it.
If the bearings look at all worn put new ones in and seals.

[wmax351]

The bearings aren't very expensive. If you are in there, you might as well do them. You can buy industrial bearings rather than BMW for most.