The importance of measuring bell housing runout.

yeah thats the best video it makes it all make sense...

the hardest part of the process is getting the indicator to stay put and not fall off. look at the complex arm they have that allows the magnetic base ro be way up on the clutch surface with an articulated jointed support i.e not the stand and arm you get at the local tool shop unless you bend the credit card somewhat

the reason for the focus these days is the fact that the clerances tollerances and as you say type of bearings is now different clearances are tighter cone and cup bearings used instead of bushes or ball bearing based bearings

we are talking manual transmissions that work best on auto trans fluid not viscous gear oil

and most of the have the gear train loaded with near zero end play or some pre load for cone and cup
previously everything was just shimmed in the case and ran on bushes or loose rollers

gears are made from harder materials shafts have less flex,

these days nothing can move in any way other than rotation, unless you have enough torque to stretch the case. no play to cater for a wonky bell.

basically your are manually installing a transmission that has its roots deeply sunk in a design philosophy where the trans the bell and the motor were machined by robots and the lot was supposed to be installed by robots

we are ramming a precision cut diamond into the back end of something that is closer to a steam train than a Prius


Dave