740 Rear Bearing Noise Identification
 

Greetings
My turbo wagon [290k] while replacing park brake cable turned the left axle which responded with 'bump bump bump bump'. Didn't think tapered bearings would do such- any knowledge of this appreciated!

could it have been simply the differential gear teeth engaging?

if the other wheel was immobilized, turning a rear wheel will cause the drive shaft to rotate at half speed assuming the transmission was in neutral. lotsa gear teeth meshing in there.

on the 122 you change the mesh of the teeth by taking off the bcking plates and moving the shims around, Its newer but maybe not a lot different? if you take the backing plates off, dont; loose track of the shims. I was able to get lower gears that were new so I spapped the crown and pinoon to make it more like a wagon or 123 because the gearing got a bit too high when I added overdrive. doing so took a lot of the slop out of it , when they get all workn all the slop adds up to a car that will go jerky jerky gerky down athe raoad if you try to drive it at about 10 MPH in traffic.

there is a procedure where you out bluing on the gears and change those shims until you get it set up right.. if it's ok dont; play with the shims.