Newbie trying to diagnose trans+shaft+LSD status.

[Dr.Ling]

The AE86 is pretty new to me, but I suspect there's something wrong with my transmission and/or driveshaft and/or LSD. I assume everything on my car is OEM and not replaced.

The first thing I noticed when I got the car was all the noise / whine, sounds like it's the transmission. Sounds like I'm driving in reverse in all gears, you all know that sound, and it's only there under acc/dec. I can't believe this sound would be the LSD.

Second thing is the abrupt nature of the clutch, bites suddenly, and in neutral with the clutch engaged / pedal up, there must be contact. Normal for an aftermarket clutch, but not for an OEM I guess. After every shift / releasing the clutch there's a slight "clunk" from the rear of the car, as if there is too much slack in the driveline somewhere.

I changed trans.oil to RedLine MT90 yesterday, but no change in the whine yet, but from experience with RedLine MTL oil in my MR2 Turbo it became better over time.

As I was under the car I tried to feel for slack in the driveshaft. It doesn't move up or down or sideways, but I can rotate it by hand either way about 5 mm / 15 degrees before the wheels turn.
With the rear wheels off the ground it takes about 10 degrees of rotation of one wheel to get the opposite wheel to rotate, which to me seems like too much of slack. Turning one wheel back and forth 45degrees, the other wheel barely follows.

My current plans for the car is a total brake + handbrake overhaul, and then a KAAZ 2-way LSD, then new springs/shocks/camber plates/RCA.
I guess I should replace my ring and pinion when I change to a KAAZ?

Anyways, input needed! Any of the above sound "normal"?
(EDIT: Edited the text after checking the car again... the slack wasn't as much as I thought first... might be normal for the OEM LSD)