Post overhaul recommendations:
1. Make sure you replace the Thrust Spring. It determines the compressor nut torque. Nut to touch compressor then 80 -90 degrees of turn. About $6.
2. Get the turbo with shaft and compressor balanced. It's done individually, then together and marked for assembly reference. This turbo whined when installed after balance. The solution was to rotate the compressor 180 degrees to the shaft/turbo mark. Static balance does not always mean dynamic balance.
3. Buy several compressor housing paper gaskets just in case of subsequent disassembly. Can also be used grommet replacement to access the upper turbo oil drain bolts.

Please explain what the Thrust Spring does and does it have another name?
Do you have a picture of the Thrust Spring?
Where did the Info on the Shaft Nut Torque come from?

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84 300D, 82 Volvo 244Gl Diesel

I believe the below is more likely the correct way to torque the Turbo Shaft Nut.
"As for the tension of the compressor nut i quote from the Normalair-garrett TO3 TO4 overhaul manual, "on oil threads, after bottoming the lock nut, torque to 18 to 20 inch pounds above the drag of the lock nut. Tighten lock nut through an angle of 90 degrees. This additional tightening will result in stretching the shaft 0.0055 to 0.0065 inch, which is required for proper installation of the compressor wheel"
Turbo shaft Nut torque see post #12
http://www.calaisturbo.com.au/showthread.php?t=180324

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84 300D, 82 Volvo 244Gl Diesel

Thrust Spring = Thrust Spring. It applies the correct torque to the turbine shaft bearings, spring seals, and compressor wheel.
Description: Looks like a profile of a toothed gear, spring thickness about 1mm, and is located on the compressor end of the center housing. It is a spring.
There are several variations of Shaft Nut Torque T3/T3. I used the 90 degree adjusted for feel by instinct - about 80 degrees. Another recommendation is 28 inches of torque followed by 90 degrees.
I believe that Garrett far overtourqued this turbine at build.
Runs so sweet.