Loud knocking sound / different symptoms!
 

Yesterday my 986 2.5L started to knock from the back / (subjectively right side).

Symptoms:
- audible only if in gear and moving
- NOT happening when cruising on neutral
- NOT happening / stops to knock when clutch is presed
- NOT happening immediately from start, only when car warms up
- more audible when climbing a steep hill
- I can also hear very similar sound but not so loud when I lower the right side of the car from being jacked up.

Visual inspection shows no rattle or damage on CV axle joints, I have old bushings (140k mileage), but I don't think they would hit so loud. It sounds somewhat like someone hitting wood with a hammer somewhere in the distance, but with force.

yes, also: knocking is synced with wheel rotation. Same speed of knocks when in 1st, 2nd, or 3rd gear but the car moving at same speed.

Bad universal joint on the rear axle.

Where is it located and what to look for when inspecting it?

In your original post you stated " Visual inspection shows no rattle or damage on CV axle joints " please explain exactly what you did or what this means . The axle universal joint mentioned above is the same thing as the CV axle joints . Usually but not always the first sign is the CV joint rubber bellows/covers are torn and throwing grease in the wheelwell or under the chassis . But a CV joint can be bad and still have good bellows . Classic symptom is a clicking or knocking noise as the axles rotate .

I'm changing the "coffin arms" with bushings next week, will buy an axle joint from a dead 986 I found nearby to have it in the trunk when I'm doing the bushings. I'll remove the CVs and examine them.