Zed Head

Found him, lurking. Coincidentally, I just watched The Thing the other night.

I'm pretty sure that, within the Z and ZX family, the exhaust hangers, one or two, will ID the ratio change. I have a 78 Z 5 speed and an 83 ZX and the casting changes are there. 78 has two, 83 has one. The speedo cog bolt orientations also. If you get in to the odd truck or Maxima transmission, maybe not. Some of the later 5 speeds are actually shorter overall also though, so you're right - best take a bunch of measurements. Pretty easy to mark front and back shafts and see what one turn in the front gives in the back.

"3/4" is not very hot. There are numbers on the gauge also if you want to estimate temperature. But a thermometer in the coolant will tell more. All that you've described is that the engine runs better cold than warmed up. Might still just be running lean. Don't get distracted thinking that the engine is overheating until you get some real numbers.

I think that the oil companies use EP additives to meet the GL5 spec. Which is what the differentials require. Sounds like you're doing everything right. Other things that will help or hurt the noise level are the padding and/or carpeting in the back deck area.. I slid some of that silver foil insulation bubble wrappy material under my carpet in the back and it made a noticeable difference. If you have no carpet or thin carpet, throw some more material back there. Your description is a little different than many though. Mine will whine or howl, actually more of a warble, at certain constant freeway speeds but is quiet at acceleration and deceleration. So maybe you do have a differential wear problem. If it were mine though, I would buy a used one and try it first. If it doesn't work, at least you'll be able to drive while you get one fixed. I have several used differentials and they all sound about the same. They're pretty durable.

Did you replace them with polyurethane or stock rubber? The PU bushings can be tight and cause noise.

If the transmission is in neutral the drive shaft can spin instead. A stock 1976 car wouldn't have an LSD. The diffs are generally whiny and all it takes is some solid contact between metal parts, or compressed old rubber, to transmit the whine to the cabin. People don't generally rebuild these diffs because they last a long time and you can find used units pretty easily. Your best shot at getting rid of the whine is to check all of the mounting points for looseness and wear and replacing them. Have you looked at them?

I've never seen a "field-fix" document. So don't really know what that means. Did Nissan send something out or is it just word-of-mouth? The hole enlargement to avoid the issue, your December 20 post (what happened to the post numbers?), sounds interesting. Just never heard of it until this thread. Seems like it would be a well-known while-I'm-at-it for anyone that removed an exhaust manifold.

Forgot to say also, that I've seen cases where people who seemed to know what they were doing rebuilt their transmissions with "kits" and they turned out worse than used factory parts. There's a guy on Hybridz who went through all of the various possibilities building a racing transmission. He ended up paying for the Nissan synchros even though they're about $50 each. The kit synchros just weren't very good. Here's a comment from Oliver at ZSpecialties about synchros, and one of his kits. Be careful. Might be best to use it as-is. "Rebuilt' doesn't guarantee better. http://www.datsunstore.com/syncro-ring-through-7083-p-1458.html http://www.datsunstore.com/trans-complete-rebuild-wsyncros-speed-7783-p-1496.html

Well that's interesting. And your tech seems to be saying that the kit synchros are a different size? You didn't say where the kit came from. I've never heard of fiber synchros for all five gears. But I have heard of modified steel synchros in place of brass. I don't see how the tech can see enough of the synchro face to determine brass or fiber. The teeth are still metal in both cases. Might get a second opinion from someone who knows old Datsun parts. You don't want someone in there who doesn't know the transmissions. Even the "kits" that are out there are incomplete and come with wrong parts.

I'd still like to see the factory documents. Sometimes in a local area one guy will get the reputation as the guy that knows things. But he's really just another guy making his best guess. And I could easily see going up a size after screwing up the threads drilling out a broken stud. Seems like if the small stud was ID'ed as a problem that there would have been a recall or an if-the-manifold-is-removed fix TSB to upgrade the studs before they broke.

There are actually ten support points ID'ed in the FSM.

I have a disassembled ZX 5 speed in the garage for reference. But there are also pictures around the internet.

Where did you get the "kit"? Not really clear if you're saying that the tech found black fiber synchros in the transmission, or if he found them in the kit. You say he's not sure if the new brass synchros will work because they're a different size. New from the kit or new from somewhere else. No offense, but it's not clear what's what. Do you know where the transmission came from? And are you sure the tech knows black fiber from steel?

You're right, it sits still then starts moving, then there's the noise, and it stops. Starts moving at 43. Maybe pull the belt for a test. The air filter is metallic. You might pull those and see if the noise gets louder or goes away. Noise will come back through the intake manifold faster than the air going in.

I only heard two "clunks". I assume that you turned the engine off then, it didn't die on its own? Sounds like a spit-back through the carburetors, more than a clunk. On the video anyway.

Is there a TSB out there? I love reading those old documents, they're educational. The exhaust manifold would be a tough material to work with, for enlarging that hole. Probably need some sort of grinding media, like a Dremel tool.

It's the distance to where the fork rests, from the bearing contact surface, that matters. Marked up a picture to illustrate. The bearing is only pressed on to the collar. It's replaceable. That's why the cluthc kits often come with only bearings, and people get screwed up. The good kits have a collar that matches the pressure plate. The best way to tell which five speed you have is to measure the 5th speed ratio by turning and counting. The way to tell early from late is easiest by looking at the exhaust bracket hanger(s), at the very tail-end of the transmission. Late has only one on the driver's side, early has two, one on each side.

Yes, from the contact surface on the ear. Others have determined the same 92mm number, EuroDat among them I believe. There's a thread out there somewhere.

Ack. So many parts and so many possibilities. Best to remember that the throwout bearing collar height is designed to match the height of the levers it sits on in the pressure plate. Collar and pressure plate are a matched set. 92 mm (+/- an mm) from the surface of the flywheel to the surface that the fork tines ride on is the key dimension. If you have that number you will most likely be okay. I will never install a transmission again without confirming that measurement. Attached a picture, not perfect but I think it illustrates. Edit - almost had the perfect post but had times instead of tines. Carp.

I was going to say if that's a Rebello motor why not ask Rebello? And heat range is more about keeping the electrodes hot enough to stay clean but cool enough to avoid pre-ignition. Indirectly related to engine temperature but evaluated independently.

What Diseazd said. All you'll need to do is get the little half-moon facing forward, on TDC compression, instead of TDC exhaust.

On my 76 the knobs are rubber (black with a white stripe) and just pull straight off the metal lever end.

I have several exhaust manifolds, and three different heads and I've never seen a wear mark on the outer exhaust studs from the manifold touching it. The three center bolts locate the manifold and there's a pretty big gap around the outer stud holes when everything's clamped down. For the 280Z's and ZX's anyway. The stud is clamped at the top and the length of the stud is free to act as a lever on the base of the stud. I think that it just moves back and forth with every heat/cool cycle. The differential is greatest at the ends since growth is away from the clamped center section. Add in the tensile forces from clamping acting on the narrower root of the thread and it seems reasonable that the outer ones break most often. Like breaking a piece off of a coat hanger. That's my fatigue theory in a big nutshell. Someone could probably design a clamping mechanism that allows the manifold to slide under the clamping nut and washer to remove the side load. It would have to be super durable though and would probably cost a lot of money.

Here's what you'll be looking at. The end of the lever where the cable attaches is at the upper right.

I can't remember for sure, but I think that if you remove the front panel/face plate over the heater controls you can easily see the levers and cables that move the various parts. Might be easier than a mirror, although I do recommend the mirror also, I use one often. Pull the rubber knobs off of the levers, remove the screws and pull the face plate off. It's not super-difficult. If you try the mirror, make sure you have a bright light. Sit in the passenger seat and position the mirror and light and you might able to see if it's moving the watercock lever or not. My car had a bent cable which wouldn't push, and pushing is what shuts the watercock. You'll probably use the mirror and find that the lever isn't moving, then take the face plate off and find a bent cable. But Captain Obvious wrote up a whole thing on using Honda watercock valves in place of the expensive Nissan valves, if you find that the lever is moving but the water flow isn't controlled.