Couple questions about re-indexing t-bars
 

I want to bring the back of my car down about 3/4" before it goes for alignment. I'm just thinking it through before I start and want to disassemble as little as possible. To that end:

Can I unbolt the damper and lower the trailing arm / spring plate until it's not under tension anymore, without unbolting the inner cv joint from the gear box?

Can final adjustments be made using the eccentric bolt, while the spring plate is still bolted to the trailing arm, or do the two need to be separated with zero load on the t-bar in order to use the eccentric?

lowering
 

yes, but answer to second question is lift car/dampner unbolted, just enough to remove weight, otherwise you won't be able to adjust easily.

this isn't a one time adjustment to get it right.

So yes the drive shaft can stay in place?

And yes the eccentric can be used provided I lower the trailing arm down and unload the T-bars?

Sounds ace.

Unfortunately, you will need zero load, no need to disconnect the cv joints.

Make absolute certain the floor is level.

Yes, you can use the eccentric to lower her if it has room. If not then you will need to re-index. remember lowering her will give you more camber and may also likely more toe in, but that is the shops problem :-), take your own measurements before and after to make certain they actually adjusted the rears, which are PITA.

Also remember, after adjustement/s roll and bounce on the car to let her settle to a close to normal state then measure.

If you are going to use a shop to do the suspension tuning (which should include corner balancing), you might want to just let them set the ride height at the same time. Chances are, they will redo the indexing anyway to get the corner balance right.

If you are not using scales you are chasing your tail