Zed Head

Just bend the four little crimps back, a pair of pliers works well, and pry the top off of the plastic base. Work over old newspaper or similar so the rust doesn't get your work bench dirty. Edit - there might be a ground wire connected to the metal cover on one side. I think that's why my picture has the cover just tilted open instead of removed. Post a picture...

There's a constant battle going on between engineers and materials people, and between design and manufacturing. The Nissan design looks like a typical "make the cheapest material work" design. Typical automotive principle. Nothing wrong with it, it worked. But it's a complex design so without the tooling, will be difficult to reproduce. Whiteline's product looked promising, and the use of materials as the vibration damper instead of the design looks right.. I think that they just did a poor job of selling it. I'll see if I can find that thread I mentioned. Found it. The Advanced Search engine of the site actually works pretty well! Needs promotion. Edit - found their site from the picture inthe other thread. Looks like they just stopped making the mustache bar bushings. Maybe they're falling apart? Maybe MSA can be a supplier if they come back. https://whitelineperformance.com/amfinder/?find=1976-nissan-280z-base-128907

Weird. I noticed that the grooves didn't seem obvious in your pictures. But they didn't seem that obvious in mine either. jmortensen knows a lot about diffs. He might have some thing to share.. @jmortensen

C'mon Euro, you gave in! Now we're just a service, like Google.

Motorman, all those 240Z's and it's unfamiliar? Buschwacker, just having fun. But you have to share more. Otherwise, it's work.

What kind of car is it going in to?

Vagueness leads to more vagueness... But it's fun for us. Welcome to the club! The answer is - one still has the crossmember attached.

Are you on a phone, where you can't see the pictures or download the FSM? It's all there... Tapping is unlikely to help. But good luck anyway, you never know.

Actually, those three get power from the ignition relay. My car had a mysterious blue wire to the ignition switch in addition to that box of rust. The relay is over by the fuse box. There's a diagram in the FSM, BE chapter. The 280ZX igntion relays will work, they have the same pins, but have an extra dedicated ground pin also, so they get a different part number even though the'll plug right in. Nissan moved the relay to a dry spot behind the glove box in the ZX's, I got a spare from a wrecking yard. I replaced my 76 with a 78 though, that I had from a parts car. Somehow it survived.

Whitehead used to sell Whiteline low durometer PU bushings but it looks like they ran out of stock. They removed the listing, with no reference (poor web site management) and other web sites show "out of stock". Somebody just reported installing a set, but I can't find the thread. It was recent. He said they were quiet. https://whiteheadperformance.com/product/whiteline-differential-moustache-bar-bushing-kit-w91045-datsun-240z-260z-280z/

The axles on the ends of the CV shafts are the same as the short stub axles used with "u-joint" half shafts. Here's a picture from 1983. They call it a universal joint, some call it a CV, apparently it's not really a true "CV", yadayada... They show the same diff with both types of axles. It's the Rear Axle and Rear Suspension chapter. So if the diff is the problem, you'll have the same issue with the short stubs. Easy to test though. You'd need to unweld that adapter also, or swap the hubs. Bummer that you're having this problem. Can't emphasize enough the need for taking good solid accurate measurements though. No offense, but you still haven't measured the distance to the diff groove and compared it to the distance to the shaft groove. Everything centers on those grooves and that circlip. The concept is shown in the picture. Numbers, numbers, numbers.... You might find that you can swap open R200 parts in to the CLSD diff. Maybe you can just fix the diff. If you have the time and patience it might be worthwhile to remove the open diff and set the two diffs side by side. Then you can see the circlips and how they work and where they sit and pop some axles in and out of the open diff. Maybe you'll have an "ah ha".

I was trying to define "all the way". They don't go in until they won't go any farther, they go in until the clips seat in the groove. I would still focus on measuring the grooves and where they sit. And the width of the housing and whatever other numbers you can get. The numbers will tell the story.

Those all start at one spot but a tap with a hammer might not be enough...

I got 8 5/8" across the back of the housing. Maybe 8 9/16". Eyeballed from above.

I notice that the numbers on the top of your diff are different from mine (see my earlier picture). Mine ends in N9000. They should really just identify the R200 housing so you'd think they'd be the same. Maybe somebody found one of those old R190's. Maybe they use different axles. Measure the width of your diff across the back and I'll measure one of mine.

It works for some people. It doesn't work for others. That's why we collect old parts. Some people have found the loose connections in the connector, not the ECU. Peel the rubber seal back and check the connector.

"Seat" is when the two grooves are aligned, with the clip in both. You must be pushing them beyond "seated" to cause them to interfere with each other.Seems like your diff grooves must have got damaged so that they don't hold the clip in place tight enough so that the axles can slide through. You have a run of the mill R200 and plain old R200 axles. You really shouldn't be having these problems. The clips should never have been removed from your diff either. t does look a CLSD too. A picture from the back showing those holes would be more informative though, showing the internal ramps. I dragged my 280ZX CV axles off the shelf and measured and got the same axle lengths that you showed on the first page. All of your parts are right, you just have to get those clips to stay in the diff groove while you push the axle through. I'd focus on bending those clips wider until they're too big to fit in the diff hole then compress them just enough to get in so that they'll have "spring" left when you push them in all the way to the groove, so that they'll spring open and be bigger. I'm sure that the factory has a special tool that maintains maximize size and spring pressure during installation. You might have damaged yours.

Here's a good thread and its link.

I think my logic on the pistons might have been off in my other post, but it really seems like those pistons are stuck closed or the throttle blades aren't opening. I think that if you were lean you'd get some popping or bucking. But you're just describing nothing happening. Maybe your oil leaked out or viscosity changed.

If the car was in gear and engine turning but the tach dropped to zero that's a sign that you've lost spark. But there are many ways to lose spark, from complete power loss to everything to a bad ignition module. It's one of those clues that you can build on. Your fuel pressure probably stayed high when it was running rough because the intake vacuum was low because it was running poorly. It was probably the other way around, pressure dropped as it started running smoothly. Just a guess. Trading cause for effect. You're at the point where it might be worth your time to try an HEI module. It's a good thing to know anyway because the old ignition modules fail on a regular basis. It's just a matter of time before yours does, if it's not failing already. You can get a BWD brand at any auto parts store for about $25. That's what I'm using now. I actually have an old 1978 module in the garage that I had wired in to my 76 for a short while, after my original module failed. I don't know where Ridgeland is and don't know when I'd have time to package it up, but if you get in a bind I might be able to get it out to you. But, long-term, it's just another old module on its last legs anyway. Better to go with the HEI.

Any chance the exhaust system is involved? Also, just to distinguish between an RPM limit and a power limit, could you try up-shifting early? AKA short-shifting. See if you can go faster even though you can't get the RPM up.

There is quite a bit out there about bad solid state external regulators. I don't think that you can classify them that way. Just pick a quality brand.

If I read the operating description in the FSM right, the pistons control air flow and the pistons are controlled by intake manifold vacuum. So, basically, if the pistons don't rise to let more air in then the engine is effectively throttled. I'd like at where the pistons vacuum source is, and if it's possible that it's blocked or lost. Maybe the carbs are loose, causing a big vacuum leak, or there's a fitting or plate that's loose. Seems like the pistons must not be responding to intake vacuum is what I'm implying. They're probably open a certain amount for idle and low RPM, so you do get some response. It's a neat concept, but the carb's air opening is controlled by a secondary mechanism, the piston, not a primary one, like a throttle blade. If your throttle linkage is working, seems like it has to be the pistons. Assuming that the other engine parts are correct, like ignition and cam timing. I could be way off, I'm just using your problem to learn SU stuff.

It just presses and snaps on. Plastic on plastic, if I remember right. But the plastic bits on the inside are usually worn. Look inside the chrome cup-shaped piece and you'll see the remains of what was supposed to happen. I had to pick up some wrecking yard parts to get one that would stay on. Never mind, those are 280Z details. Looks like 240Z is different. I looked at your picture.

It's always at 2500 or it's standard for when the engine dies? And did you power the fuel pump to get the 25 psi, or just look at the residual pressure? Here's an old story I bring up sometimes - I've had my 76 and a 78 parts car both refuse to start when I had the tachometer removed. The 76 also refused to start when the tachometer resistor fell out (I had unwrapped it from the harness just to get a look at it). To me that would imply that if the tachometer circuitry was messed up enough inside that you could get a no-run condition. It's an odd thing and the phenomenon went away after I switched to a GM HEI ignition module. But it seemed like the quality of the signal on Pin 1 to the ECU must have been affected to cause it. You could test your system by removing the tachometer inline resistor and seeing if your engine will start. If it doesn't it's at least a possibility that the tach is involved. Doesn't give you much direction but I suggest staying open-minded. You have a weird problem so it might have a weird cause. The GM HEI module swap is very simple, wiring-wise. You can bolt it to any car part close to the coil, as a test, if you wanted to invest $25 and some time.