Zed Head

You can buy them at any auto parts store. No need to wait for delivery, just get them when you need them.

You're going to have to give a better description than "no click stop when I flick it with my finger". Make a video.

https://www.classiczcars.com/forums/topic/53344-drivers-side-door-locking-mechanism/?tab=comments#comment-623584

Since the thread quality isn't an indicator of the quality of the potential failure point your worry level should be the same. Your "new" used axle is just as likely to fail as your old used axle.

77 survivor. Going counter on the main picture, pointed right. Rebel. https://bringatrailer.com/listing/1977-datsun-280z-50/

Quiz him on what was good about it and what he would have changed if he still had it. Then go find one like that.

The diff mount seems to be sitting high. Look up in this hole and see if there is a nut on the threaded stud. Stole from Namerow.

Interesting plot showing vaccination versus virus.

Have you checked all of your grounds? Grounds are more important than most people think. Weird stuff can happen. Might be affecting the ECU operation. Random internet thing about ground loops... https://www.bapihvac.com/application_note/understanding-ground-loops-application-note/

Your test results don't seem to match what happens when the engine is running. Why focus on the AFM when the TVS has the biggest effect? I don't know that the AFM numbers are as critical on the ECCS systems since they have closed loop control. That's why they give a wide range in the specs. Can't offer much help. Your car seems to be haunted. Weirdness abounds. Lifting the distributor cap to fix a rough idle...unplugging the TVS makes it run right even though it tests correctly... Mystery.

Unplugging the TVS would tell the computer that the engine is not at idle. That is all. This causes certain things to happen. I'm not sure exactly what happens but the dramatic effect that you see suggests that your TVS is short-circuited or the wiring harness is, showing the engine at idle all the time when it is plugged in.

This can't happen unless the wheels are spinning or the differential is broken. If the differential is broken it's permanent. There's no not moving then moving.

The internet is an amazing thing. I tracked down a guy who was ripping people off and using the money to pay for his wedding. Just for fun, I didn't share the info with the victims, just told them it was "out there" if they wanted to find it. The dealership might have the VIN and the VIN is used by most people that sell 240Z's these days. https://bringatrailer.com/datsun/240z/?q=240z

Add as much more information as you can. This is nowhere near enough. Not even close. Pictures, dates, names, dealership, etc. will all leave traces on the internet. 72-73 240Z is everywhere though. Well?...

Clutch problem

Automatic or manual?

No. heyitsrama is probably right. Looks like your exhaust system has broken before the muffler. That's why it sounds like a straight pipe. Your timing sounds retarded also. Have you set it with a timing light recently?

You should create a youtube channel and put your videos there. I've only been able to play a couple of them. Your latest one won't play.

https://www.technoversions.com/DiffMount.html

Stripped threads are not the common failure point for the 240Z axles. It's the base of the threaded portion, the transition to the splines.

The strap is visible in the picture. It looks like a strap. The noise is caused by the nose of the differential lifting up and bumping the stuff in the transmission tunnel and/or the diff nose dropping down and banging off of the crossmember after it lifts up. p.s. don't mess around under there unless you have some good jack stands supporting the car. It's a lightweight car but still heavy enough to crush.

Didn't even see this one go by. Very nice. https://bringatrailer.com/listing/1974-datsun-260z-44/