Clutch wear measurement "in place"?

[Bmmerpilot@xxxxxxx]

Among other things, it's time to have the driveshaft/center bearing rebuilt, 
and replace the shift linkage wear components on my '89 325i (235,000 miles). 
Is there any way to measure the installed thickness of the clutch disk 
without dropping the trans? (I have calipers, etc.- could make up a stack of 
feeler gauges and measure them, I guess, if I can get access).  Certainly 
I'll be "in the neighborhood" down there, don't mind doing the job, but the 
clutch seems fine, so I'll skip it if the disk is less than 50% worn. Anyone 
know what the "installed" thickness of a new disk is, and  the wear limit?

TIA

George W. Traminer
Martinez, CA

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