zKars

Cap’N thanks for the excellent thought process, yes, hard to say what caused what. So plainly I should weld the nut to the main shaft AND them both to the washer, and nothing bad can happen. Right? Anyone want to buy a slightly used 5 speed?

I plan to spot weld the big nut to the big washer to prevent it from turning, effectively duplicating the function of the ball. Drilling the main shaft for the later 5mm pin upgrade is not possible due to incredible hardness of the main shaft. I had to re-surface both the washer and the face of the gear it touches (sand them flat) in order to get them to turn freely when the nut is torqued. Both were a bit chewed up but there is virtually no clearance when tight. Just enough for an oil film. Can’t let any defects remain that can get the fit in trouble again. Regarding the possibility that a too-small ball was used when I replaced it, well it’s possible. If I lost that ball and replaced it with another, but my replacements are the “same” size within measureable limits. Seems the presence of a bit of rust and slightly loose nut allowed that washer to turn under the tremendous torque of a mighty L series and caused the deformation that turned into a lock up. Only guess I have at the moment.

And of course we will speculate endlessly about what caused this in the first place. Notice the presence of what I can only say is rust near the failure area. It was also under the bearing sleeve that this washer tightens against Only spot I see any such rust. Trans was filled with Redline MT 90. I will say the big nut wasn’t as tight as I likely left it. Peen area was still peened, but I’ve seen trans with very loose big nuts where the peen was still in place, as if it backed off one (or more) full turn then stopped back at the peen area. I know from experience, I no longer un-peen before backing the nuts off, they quite happily un-peen themselves as I turn them off (hand wrench, yes long hand wrench), so that collar/peen area is really pretty soft. This nut was NOT backed of to loose, just not to torque spec.

So. How to “fix” this. I might have one of these larger pins and matching washer, I guess I can drill out that little half moon hole to the PIN size and put it back together. So why is it such a big deal to not have these washers rotate as you tighten the main nut or in road use? Once the big nuts are tight these washer ain’t gonna go no where, and so what if they did rotate some? Same ball and groove on the big washer on the front of the counter shaft main bearing. I’m tempted to just leave the ball out and bolt it all up…..

Now in the next trans revision, this was apparently a known issue because , here is what they did. Big fat pin and much larger slot in the washer.

Seems the little ball decided to try to leave home for greener pastures. In doing so, it deformed the groove in the washer, causing it to lock against the gear face next to it, effectively locking 5th gear to the main shaft. Usually it hits the sleeve under there where the sleeve bearings run, and not touch 5th gear. I hope you can see the deformed area at the top of the groove arch. This is enough to touch and lock quite solidly against 5th gear.

The tranny was indeed locked up. Nothing that you can see on inspection of gears, syncros, shift rods etc. Trans shifts ok into every gear except 5th. My first guess was a loose big main shaft nut. Nope. When in neutral, you turn the input shaft by hand the output shaft turns and is hard connected to the output. Oh oh. Something under one of the gears or synchros has a failed (sleeve bearing?) and is not allowing each idler gear for each speed to spin free in neutral. Hmmmmmm Well, start at the back end and start to take 5th gear apart. Get the big nut off (it was still staked and tight), and then try to slip off the fat washer behind it. No move-y. Get a hammer. No move-y. Get a chisel to get between that washer and 5th gear. Hit it. No move-ness. Nada. This is the one with the little ball and groove that prevents it from moving. Well after using more and more “assistance”, the washer finally comes off. And what should I find? Behold

Friend had an exciting day yesterday. 75 280 with the early Z (78-80ish) 5speed (the one with no reverse lockout). Pulled away from a stop light in 1st, got about 10 ft, and BANG!!!!!!! And the car stopped dead. Needed a tow home. He drives the car 50,000 km a year, drives it daily. Has a modified L28 “maybe” 200hp. Not a sense of anything going wrong, just WHAM. I rebuilt this trans over a year ago with the usual bearing and sychro refresh. He pulled it last night, brought it over this morning, we tear it down. Found something I’ve never seen before.

Well the datsun spline is 10.7 mm OD and also has 16 splines, so maybe just start with a Chevy adapter and turn the splined part down to 10.7mm, deepen the splines and Bob’s your uncle. the OD of the non-splined part below the Datsun splines is 12mm. Darn close to 1/2”, so that adapter might just slip right over and work once you “adjust” the splines a bit. Or put Chevy crank handles on the Chevy splines and be done! Who’s going to notice! (Sorry had to add that)

Two common areas here. The starter switch as mentioned, or the deteriorated crimp and loose/dirty spade connector that attaches to the spade on the starter. I’ve cleaned the femaile spade on the end of the wire and still had this bad behavior, only to find out there was only one crusty strand of the wire still in the crimp. Remove the spade connector, strip back and clean the wire strands, and re-crimp to a new spade connector

There are three distinct styles, 240, 260/280 to sometime in 76, then another in 77-78. The 280’s are different in the right side light/wiper stalk location, it is canted up 15-20 degrees on the 74 260 and onward, so the hole in the shroud is moved up, well the two halves of the hole, so the top hole is larger and bottom hole is smaller. The late 280 shroud is bigger and wider overall.

The original poster requested the thread size and pitch, which I provided with additional details about the fastener. I apologize for the my use of the apparently forbidden “Phillips” term when describing machine screws on a Datsun. I shall from now on use the non-gendered term “X” or “cross” as a generic pronoun to describe screws of this style. Then the readers of the thread can choose to find and use hardware with the drive type of their choice, be it “phillips” or “JIC” or “posi-drive” or whatever the drive of the day is. Sometimes you just need to put the bumpers on with the hardware that locally available and not the exactly correct fastener. Oh, and let me also apologize for an early morning snarky response…..

Assuming you mean these, the screw is M5x0.8 thread, round pan head, phillips, star washer, 10 or 12mm long.

https://resurrectedclassics.com/en-ca/collections/sheet-metal/products/1970-1978-datsun-240z-260z-280z-steel-passenger-side-fender

Well here’s my thinking. The rod is under compression as long as the car is moving forward, I’d put the compliant material in front. I’ve noticed in actual practice, just putting new rubber on both sides with proper torque gives you wonderful ride and handling. Having poly on either side, front especially makes for more road shock feel and noise in the wheel when you hit a pothole. Unless you’re racing and trying to keep very very tight suspension geometry in spec I can’t imagine why you’d put poly on either side of the TC rod mount. Like putting poly on the transmission mount. You want to hear your gears why?

Tighten the screw…..

Just to check if there was any correlation between which AFM’s have rivets or screws holding the cover on, I found that all of the 5 pin connector AFM’s that I have used screws, where as all the 7 pin connector-ed AFM’s had rivets. So 75-77 with internal fuel pump contacts were rivets, then all the later ones had screws. I also have two turbo AFM’s and one has rivets and one has screws. Humph. Just when you think you have a correlation…. Might just be a “where were they made” kinda thing. I am tempted to add, “Anyone want a slightly used AFM cheap?” I’m collecting them why?

I believe the un-mentioned issue so far is moisture. Have you routinely drained the water from the bleed valve? If you look at the tank you will like find a "Best before" date like on your milk. Compressed air cylinders have a safe working life limit as well. 27 years is likely stretching that a bit, but I think I have milk in the basement fridge that might be that old.....

Just an update regarding carsteering.com racks. And I love to make posts in really old threads..... Checked today and Car Steering is still listing racks for the 280 as having 10+ in stock. Price is $260 + shipping. 240 racks are out of stock. 280 racks are same just need the right bushings for wider flange on the Left side. https://www.carsteering.com/buynow/1976/Nissan/280Z/Rack_and_Pinion/80-70087_AN Don't forget that Techotoy now makes all new steering racks for S30 https://technotoytuning.com/nissan/240z/ultimate-steering-rack-240z $695 list. $895 with their tie rod ends

I'm not exactly close but I can scrape one up for you if you can't find one closer

Arrow on the insolator goes forward. Good find, most don’t notice. As to the cross member, put it on which ever way fits once the trans in in the car. Is the center hole in line with two holes that mount it to the car? If so, then it doesn’t matter which way around. If the little dimples line up with the tips of the bolts on the isolator mount, all the better

Yeah, now says $12.88. No clue where I got the $29 from. Could have sworn that the first price I saw. the older I get the more I’m amazed at my mind. Usually not in a good way. Anyway, hope this helps all of us Transmission builders. Enjoy

The left hand threaded main shaft nut on the FS5W71B transmissions has been NLA for a while. Smome member here had some made, but guess what? They are back in stock at Transmission Parts Distributors. Just got an email today. Bit pricey, $29 USD..... ouch.... https://www.transmissionpartsdistributors.com/fs5w71-transmission-nut-for-main-shaft-left-hand-thread-fits-datsun-nissan-81-nis-204/

Been busy continuing the conversion, shoveling snow and taking care of family matters. All is going well, will continue this discussion shortly. thanks for the kind words everyone.