Z31.com Wiki

Z31 driveshaft and other driveline compatability information

Basic Driveshaft Information

All manual transmissions are the same length, so hence all manual driveshafts for two seat cars are also the same length.

Transmissions each have their own unique slip-yoke on the driveshaft, and length for their application:

84-89 Automatic (2 seater)
84-89 NA manual (2 seater)
84-86 Turbo manual (2 seater)
87-89 Turbo manual (2 seater)
84-89 Automatic, 2+2
84-89 NA Manual, 2+2

In addition, the joints are not the same size in the N/A and turbo (at least manual) shafts; turbos are bigger so you cannot simply swap yokes or diff flanges on the shaft. On a side note I have only seen replacement-type joints listed for the turbo driveshaft's joint sizes, not the NA. It's easy to see from this information that if you want to put a turbo manual transmission in a 2+2 car, you will need to have a standard turbo driveshaft lengthened (re-tubed) or a custom unit made

There are two diff flanges:
84-86 - 38210-Y0800 - rectangular bolt pattern
87-89 - 38210-10V00 - square bolt pattern

You can swap the differential companion flange on the diff relatively easily with a steering wheel puller. Be sure to re-torque the pinion nut after swapping the flange!