Have you tested back lash with a dial indicator set up?
Should be in the .010 to .015 +/- range.
If all is not correct, you can end up with noises and possibly gear wear if R/P to tight.

 

Thanks for trying, but that's not what I'm talking about at all. There are no problems with the gears at all. The only thing I'm dealing with right now is poor traction-lok performace after rebuilding it with new clutches and shims.

EDIT: The shims I'm talking about are the shims that affect the spider gears, not the carrier. That might have been what confused you.

 

The replacement clutch set from Ford should load right in without any special setup.
The S spring is what puts the pressure against the clutch packs, so there should not be any space as you are saying after the S spring is in. There is nothing else to wear outside the clutch packs to cause the loss of pressure the spring exsert against the packs.
The only other way these packs are used is in a drag 'car'.
They are often installed with an extra space plate each side and a truck S spring used to make the rear act nearly as a solid axle with the use slicks behind high horsepower.
Problem is that the car is hard on tires and axles on the highway with a rear that stiff.
Good luck.

 

Raybestos makes an 8 clutch pack upgrade vs. the stock 6, that will significantly tighten up the trac lock.

 

I ended up tearing it apart again in July and reused 2 of the old clutches for a total of 8 now. It is much better now and more of what I was hoping for.