Zed Head

If I was in this situation I would work up a short list of "project stoppers". Bail-out points, where I knew I wasn't going to get the results I wanted. So far, it looks like the expectation is for something that shifts like the current 4 speed, but has an extra gear. But if you've only experienced your good-shifting 4 speed, you might not really understand how a simple thing like a 2nd gear that grinds at 3000 RPM can destroy your fun. Or a 5th gear that pops out while you're driving, or sloppy shifting from loose shift forks. That's your dilemma, how to evaluate the quality of the parts, without having tried them. Maybe we could come up with a list of specific things to check, like the detents on the shift rods, or the play and wear on the shifting forks. Some of these things are easy to examine, like the shift rod detents. If those are wasted from banging gears, the replacement cost might put you over the top. Another thing that cna hide but look fine, is a broken synchro gear. They can break in one spot but the break can stay closed. That's why you need to get bright lights and a magnifying glass and pry around or tear things down. That's how I look at these projects. Avoid sinking too much in to it until you can lay out the path to success.

I like the installation tool. "Brinelling" has been brought up as a potential problem when using the nut to pull the bearing races in. Just doesn't seem like the best way. Yours is better. You did use it for the bearing, or just the seal? How do you knock the center out of a bearing? Just beat it out? Didn't realize that you were going to use the ZX axles, and that you bored the hubs. The boring is interesting because I think that you could go a little deeper if you wanted more clearance for your axles. Use a shorter "distance piece" although that would probably make it weaker overall, leverage and loads and all that. Hope it all fits together well. Don't forget to leave a little note in a bottle for a future owner.

A good examination of just the 2nd and 3rd synchros might tell a lot. Not sure which are easiest to remove. If you know anyone or have a trustworthy shop nearby you might just take the whole gear assembly over as-is and let them take a look. A guy who's seen many transmissions could probably tell you if a new oil gutter and reverse idler is going to produce a driveable unit. The problem with banging the gears and working things hard is that it torques the shafts and bearings. People often find pieces of the bearing retainers on their magnets. The shift forks get worn and cracked, their retaining pins can break. There are just many small things to check, especially on an unknown unit. On the other hand, I've installed transmissions then pulled them back out a couple of weeks later. It comes down to what you're handy at.

Looking back over your thread, I would really recommend that you run through the inspection procedure in the factory FSM. You started out as just replacing a broken oil gutter, but now you're sinking money and time in to what looks like an abused transmission. I suggested the the chipped reverse idler was the result of an angry driver with a bad clutch but on second look somebody really had to pull hard to do that kind of damage. They didn't care. Looks more like they were banging gears and missed the 5-4 downshift, repeatedly. I stole a decent picture from duragg's thread showing new synchros and good dog teeth. You need to look at them straight on. Look for symmetry and sharp peaks. There are clearances you can measure to see if the synchros are worn. Described in the FSM. Also, from what I've seen, the broken gutter happens when people disassemble the transmission. Looks like somebody's already been in there. Still looks like a good time to pause and ask what you're really expecting. I get a queasy feeling looking at what you're seeing. What's the history on the transmission? You can see the end of the thread on that shaft. Follow it in and see which way it turns.

Seems like you're forging ahead and making good progress. But you might pause and digest what you've learned, while reading through the thread below, and the links inside it. You're at the pint where you can decide to just throw it together and hope or get into some very fine details to ensure it works well. Lots of good stuff and some good branches out to more -

I've used Hylomar Blue on the recommendation of others. It's non-setting so you can take several tries to fix your errors during reassembly. Like assembling the cases with the shift rods in neutral. http://www.hylomarsealant.com/ Forgot to say, it works well on the adapter to case seams also. That's where the errors happen. I think that I would use a Nissan gasket for the front cover. The gasket is actually part of the clearance stack for the countershaft bearing, which has a shim underneath. It seems that Nissan got their manufacturing act together and everybody ends up with the same clearance. but if you use a different gasket, your stock parts might be off. The 71C uses the same gasket and was around for much longer, so Nissan has them in stock, I'm sure.

Sounds like we followed the same path. I ended up shortening the tips on my old single-function pliers so they wouldn't bend, using a pair of small vise-grips on one side so the tip clamp wouldn't torque loose, and using a screwdriver on the gap created once I got an edge over. All kinds of tools involved for one little snap ring. It took many "snap"s and sparks as the tips kept letting go while I was trying to get over the edge. Maybe that's why call them snap rings.

I hope you have some good strong circlip/snap ring pliers. Nissan used a super strong clip on that gear, probably because that's all that's holding it on. Took me quite some manipulating and tweaking to get it removed.

I think that he's basically converting a "PCV" to a "CV". The PCV brings fresh air in through the valve cover to cause movement of crankcase gases through and out. The old-style 40's-60-'s era vents just allow overpressure somewhere to go, but there's no "cleansing" action. No flow, it's static and only the excess gas gets pushed out. The rest of the blowby just hangs around, dropping its contaminants in to the oil. Like an old Chevy with the vent on the oil filler tube. The dip stick always comes to mind when the discussion turns to pressure. It would get pushed out if pressure was significant. At least mine would, the seal isn't very tight. It's basically a gravity seal.

The hose from the valve cover should release plenty of pressure, I'd think. The crankcase and valve cover are essentially the same cavity. Hope is good, but that #6 number is pretty low and shows all the signs of bad rings.

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I'll go ahead and get it removed, run by a postal place to see the cost, probably just flat rate in the box USPS, and PM you some details. A day or two. If you're in a hurry, let me know. Let me get it off the shaft first. You never know, I could be defeated by a circlip.

Good stuff here. Worst case you find out that the disc was already there and it falls out. People have made their own from thick pieces of rubber though. You can get more flex by unbolting the distribution block down below, for the left and right discs, I think. I've done the same in the past. On the other hand you could put it back together and see how it behaves. From what I've read you'll know immediately if it's gone. Then you can go through the ordeal.

Mine's already torn way down. This is what I'm looking at. I need a better circlip plier anyway. You can have it for shipping. I got one of then there PayPal things out there somewhere. No hurry, see what's out there. See what else you need, although this box was pretty trashed. This is why I keep old stuff. Hate to see it wasted.

It's 23 teeth and in great shape. Couldn't get my old rusty circlip pliers to get the clip off though. How are your bearings/bushings (not sure what's under there)? Might be better to just pull the whole shaft, bearing, and gear complete from the adapter plate. I assume it's a press fit.

I might have one from an old junked 5 speed. Used the case for a 71C swap. I'll go count teeth and see what shape they're in.

I measured to the bearing marks on my 83 CV axles (copied and marked your picture) and the same on a 280Z halfshaft with diff stub axle. Direct outer flange to bearing race, in essence. I got 16 7/16" for the u-joint halfshaft, 15 7/16" for one CV, and 16 1/16" for the other. So my CV axles are both shorter than the u-joint half shaft. One CV is 3/8" inch shorter than the other. I didn't distinguish between left and right halfshafts becuase everything I've read says that they're the same length. Not sure why you got different lengths. I have a pile of halfshafts but can't tell which side they came from. Just went out and measured all five of my good halfshafts and one bad one. They all come out to 15 5/16" from flange to flange (the extra 1 1/8" above is to the stub axle bearing mark). The bad one, which was probably in a wreck on a parts car I had and didn't extend freely, would only compress to 15 7/16". But I've had it apart to try to fix it and it was damaged anyway. Since I only have two on my car, and I got them all as sets from cars, all of my u-joint halfshafts seem to be made to give the same compressed length.

Seems like the ZX flanged nut would be stiffer than the Z assembly. Interesting stuff. Maybe it's more than just a lock nut. I dragged a CV axle and a u-joint halfshaft out the other day and measured them. But just realized I didn't measure both CV's so need to do it again. The one CV axle I measured was 1" shorter than the half-shaft. So, in my case, 1" for an adapter. Factory issue 1983 CV axles. I'll measure the other and add it to your thread, just for the record. Thanks for the pictures.

Thanks, that's the picture I wanted to see. And there's not a lot of info there really. I wonder if other things helped also like the thickness of the washer under the nut. Maybe even the shape of the nut's clamping surface. I think the breakage is more a flexing/fatigue break, than an actual yield break. Could be all of the people switching to 280Z axles really just need to switch to 280ZX nuts and washers. grannyknot was in the process of installing ZX CV's. Not sure where he ended up.

Here's a nut source - http://www.thezstore.com/page/TZS/PROD/23-4573

I was thinking about the 240Z axle weak point. Borrowed a 280ZX axle picture from here - https://www.fototime.com/ftweb/bin/ft.dll/detailfs?userid=7DC317B08EDB4B2EA837F708D07C9769&ndx=19&albumid=180EC34916C34BD7850ED1A4EBA6F840&pictureid=0F5C07D338644ADBAE151D14EE4BFDF1 and the 240Z from here - http://forums.hybridz.org/topic/49194-differential-cv-lsd-hp-torque-r160-r180-r200-r230-diff-mount/ and here - http://www.thezstore.com/page/TZS/PROD/23-5020R Notice that the same tiny nut is used, leaving a big stress riser at the base. The breaks occur on the same diameter. The larger splined section doesn't seem to be any advantage in strength. Maybe why they went back to 25 spline. It does allow a bigger bearing though. Even the big 300ZX 39 spline axles use a small nut diameter. http://www.modern-motorsports.com/stub-axles.html

Nissan used a self-locking nut on the ZX's, so no need to stake anymore. You should too, they're available. As for damage, don't overlook that the damaged portion doesn't do any work once the nut is past it. If the threads won't damage the nut, then you might as well leave them that way. The smaller axle question has been raised before. Could be that they redesigned it and removed the stress risers that existed in the 240Z design. It would be interesting to see the two side-by-side. Or that the ZX suspension isn't as hard on the axles as the Z's.

Makes sense. I've seen the problem described before but can't remember the solution. The early 240Z's have booster and MC complications often. Matching the right parts. Year of car in the title will draw some eyes.

That's a picture of your brake booster. The tip of the rod sits in a cup at the base of the master cylinder piston. Not really clear what you did or are doing. That looks like an old dirty booster, what's new or restored? What is not working? What document has the measurements you're checking?

A follow-up thought - #6 is typically the detonation cylinder. Where head gaskets blow and rings break. Mis-set timing, low octane fuel, overheating; could be the cause of the problem. Doesn't help fix it but might help focus. Unless oil splashed up on to the valve seats, which seems unlikely at low cranking RPM, the oil in the cylinder raising pressure still points to rings. If it were my problem, I'd use a borescope to check for cylinder damage first. If there is none, and it runs well, and you get lash set right, take it out for an "Italian tune-up". Nothing to lose. Sometimes people baby their new motors when they should be using them to break them in right.