Agreed! Turned out way better than what I had envisioned, very nice indeed - kudos to both of you!

 

Thanks, guys.
Now you see what a leap of faith the project was...no way to tell if it was any good until the very last minute.
I hope this motivates Sigfrid to finish up the other side and we can move on to the much more difficult strut tower covering project.

Meanwhile, I have two projects to attack on Sprocket.
The first just popped up and is minor...the radiator drain plug started leaking, so I need either a new o-ring or maybe a whole new plug. We'll see when I get under there later today.

The second, larger project is the gauges and I'm nearly set to begin.
I have the VDO water/oil gauges ready to go in and have LEDs for all the lighting, so I'm just finalizing the dial faces. I want the stock appearance of the black/white faces but the stock Miata dials glow green at night and it's not as crisp and clear as I'd like.
This is probably more a function of my deteriorating eyesight than the actual gauge cluster but it doesn't really matter, the heart (or in this case, the eyes) wants what it wants.

And of course, looming over everything is the immanent failure of the transmission.

 

Looks great.

 

A short (and no doubt, ineffectual) rant...

I discovered last Saturday that my car was dripping coolant from the radiator drainplug (Godspeed). Trying not to lose too much coolant (stuff ain't free!) I quickly pulled it out, tossed on a new o-ring and reinserted.
Which didn't work.
Second time, as I goofily tried plugging the hole with my thumb, I took a closer look and discovered that the plug, although it originally came with an o-ring, was not really properly designed to use one. There is no relief above the threads or in the flange to hold a ring in place, so as you tighten, the oring squeezes out.
Well, that's not great.

Decided to see about finding a replacement but needed the size...and here comes the rant.
Google "Godspeed radiator drain plug" and you'll find all sorts of complaints about the plug, not a single one of which ever says what size plug they ended up using.
They all fall into the "Problem fixed!" catagory with no info as to HOW.

Best I can figure, the plug is either a 10 or 12mm, 1.50 thread, so I'm off to Autozone to get both and see.

Haven't decided yet whether I'll reveal the correct size.

Bastards.

 

What?!? You don't have a caliper to check the thread max OD and pitch or at least a Metric thread gauge to check the thread sizes?

"Hobbs, this man needs more bloody tools in his collection!"

On a more serious note, it would also be very interesting to see if the female port in the radiator itself has been properly machined to receive, capture and compress the O-ring. Although the link below is for -AN port fittings that use O-rings, the diagrams clearly shows that for O-ring fittings, this is not just a simple drill and tap female thread operation.

SAE J1926 PORT REFERENCE DIMENSIONS

 

Yes, I do have calipers and pitch gauges...I was being lazy and trying to do this without draining all the coolant, pulling the plug and quickly reinserting it.
Turns out it's a 10mm x 1.25 and it's all fixed now.
I think...we'll see.

 

The transmission gods looked down upon us and decided to show benevolence.
Sigfrid and I just picked up a 5-speed for the Z and I'm getting a trans for the FC tomorrow.

Today all is right with the world.

 

So, the Z was/is a four speed? I can't believe I've followed this and wouldn't know it was an automatic.

 

Yeah, four speed.
The first four gears are identical but we get an overdrive fifth, which should make highway driving less frenetic.
The family we bought the Z box from today had some really interesting cars...a RHD 240 Fairlady Z, an S13 with a big Infinity V-8 swapped in and a 1972 matching numbers Hemi Cuda (I think) and Mom, Dad and the son all knew their **** (the Cuda is Mom's!).

On the way over, S. and I were talking and I recommended we get a light flywheel and do the whole job at once but that would take more money than he can spare right now and the Dad brought up an interesting and previously unconsidered point.
He eagle-eyed the numbers on our block/head and correctly noted that we have the (theoretically) highly desirable later ZX block (better webbing and improved coolant flow) and asked if we'd checked the flywheel.
Well, no, we hadn't.

Turns out, the majority of that model was sold with an automatic, a differently geared diff (3.9 as opposed to a 3.53) AND a heavier flywheel...it's very possible we have the heaviest factory available flywheel and don't even know it.
The flywheel on our backup engine MAY be lighter, it's certainly worth hoping for.

They had really cleaned up the tranny, it was spotless and Sigfrid got it for $340 (he was asking $400), so he's pretty happy.

I don't know what the FC trans will look like tomorrow but it's only $20, so I don't really care.

 

Replacement transmission in hand (well actually, in the garage but...).
I've ordered new front/rear seals and shifter bushings, soon as they arrive the box goes in.
Gauge cluster mods (VDO temp/pressure and LEDs) about 80% done, should be finished tonight.

For a change things seem to be going well.

 

How adorably naive.
The decision to retain the VDO dial faces unleashed a cascade of unforeseen consequences, which required almost a full day of Dremel magic to overcome.
I'll see today if it was all worth it.

Sigfrid did some number tracking of the new Z 5-speed box and we hit the jackpot.
There were two 5-speeds available and we got the later, more desirable version.
I hope we can get it in this weekend, along with mine, so we miss the inevitable cold weather and can work in comfort.

I can't get over how temperate our fall has been so far.

 

OK, first test of the cluster was a slightly qualified success.
Everything works although I'll have to wait until dark to evaluate the new LED lighting.
With the VDOs in I finally have oil pressure and water temp data for the first time since engine install and she's looking fine.
With the engine showing 180° (where she will apparently sit forever on this 60° day), idle oil pressure is 35psi, climbing to 55-60psi over @3k rpm. This is worlds better than my recently departed old engine, which basically showed NO idle pressure for the last 75k miles.
Go figure.

There are two minor issues to address, one simple, the other not so much.
I need to slightly reposition the oil pressure gauge as a bit of light seeps out around the bottom of the dial...this one is easy (well, at least straightforward, if a bit tedious).

The bigger issue, one I've always had and never really solved, is the trip reset button.
The Miata button (or more accurately, "post") does not line up with hole in the clear FC cluster cover and is too short anyway.
I am thinking the best/easiest fix is to delete the hazy, ultra-curved FC glass (which is a giant glare/reflection magnet anyway) with a flat panel of non-glare plastic but I'll have to see what cosmetic effect that will have on the cluster>bezel interface...it might leave an unsightly gap.

Other than those two tiny issues, I'm quite chuffed and very relieved it all seems to be working out.

Sure is easier than humping the transmission in and out, which is next on the agenda.

 

Indeed it is, Sigfrid and I just finished swapping his new five speed into the Z and boy, what a difference.
It's a real "night and day" type change too, everything is nicer and the car is sooo much more relaxed at highway speeds.
The short shifter that came with our four speed will not work on the five speed and the five speed stick has a different thread, so our old **** won't fit either.
That's pretty much the only glitch in the project, the rest went pretty smoothly.

Next up- later this week- we do my trans swap.

Oh boy.

 

I just saw this re-run episode of WD where they swap in a 5-spd in place of the factory original automatic in a 240Z.

"Wheeler Dealers" 1972 Datsun 240Z (TV Episode 2015) - IMDb

 

It's really not all that terrible a job- and the fact that our car is basically freshly assembled certainly helps- but man, it sure would have been nice to have a lift and a trans jack, ya know?
I have a scrape on the end of my nose from rubbing on the floorpan...it was that close.
His cheapshit Harbor Freight floorjack just doesn't get high enough to use all the jackstand height, we had to temporarily rejigger the whole setup to drag the old trans out and slide the new one in (the bellhousings wouldn't clear the framerails)...and it was tight even then.

Despite the fact that S. was feeling sick and cranky and I'm just generally a useless old person, it still only took about four hours, which included some downtime as we figured out the sequence and then discovered he'd been given the wrong output shaft seal (which we ended up ignoring, here's hoping it's OK), so certainly not the worst one day job we've ever done.

 

Started prepping the "new" transmission for install.
Have new front/rear seals in hand, have freed the drain/fill plugs and the electrical sensors.
Trans is currently sitting tail-end up on the bellhousing and I dumped in some gear oil to slosh around and maybe clean up the inside...I have no idea what it looks like in there.
Tomorrow I'll clean it up and she'll be ready for a Friday install.

Meanwhile, I also took care of the Z shifter.
As hoped, an 8mm Helicoil screwed right into our 10mm Nismo **** and the **** now screws onto the shifter shaft as it should. I love that trick.

Not much but it's all positive and that's a refreshing change.

 

I spent the last few hours of my post-election heroin binge prepping the new box for install.
"Prepping" in this case means replacing the input and output shaft seals and that means removing the front cover plate and that means finding the cover plate.

The inside of the bellhousing was slathered with a coat of oil and friction dust...a coat so thick that the inside looked almost featureless. Wasn't till I started scraping with a wooden stick that all the nooks and crannies began to appear.
I had actually planned on taking a few low quality pics to celebrate my activity but was so quickly covered in pernicious black goop that handling anything was out of the question.

And, to be honest, I scaled back my ambitions and only cleaned enough to safely pull the cover plate without piles of crap falling into the bearings.
It's clean, just not pixel-worthy spotless.
I polished the throwout bearing snout, the pivot ball is in fine condition.
Under it's layer of crap the pivot arm rubber gaiter was also in great shape.

A bit later today Sprocket goes up on stands and the swap begins.
Sigfrid is coming over tomorrow to help but I figured I could get a lot done solo...maybe even the whole thing, we'll see.

Forging ahead with my Pollyanna-ish "It'll be fine!" mindset, I'm assuming this box even works at all- there was no shifter included, so I've yet to give it a cursory row through the cogs and getting the short shifter transferred over with the same slick feel I've been used to is a major concern.
I know all my sensors are good on the old trans, so I'll be transferring them over and saving these "new" ones for spares.

It'll be interesting to see if the cause of the terrifying knock is obvious or not...I'll feel better if/when I can confirm it's definitively IN the gearbox and not something else.

 

If there are grooves in the shaft from the seal, don't set the seal exactly where the old one was. Sometimes there aren't fully bottomed in the bore but if it is, don't set it as deep. Sometimes just a mm or so is enough to keep the seal out of the old groove.

 

Thanks for the heads up sir, I wouldn't have thought to check that.

 

Well, well, well.
Sprocket is up on stands (much more comfortably high than last week at Sigfrid's) and disassembly has begun.
Because she was fully gone through just a few years ago, all of the relevant hardware/bits/bobs came out easily.
As I approached the bell housing, I thought I'd learn from last week's mistakes and drain the trans oil...we neglected this simple precaution much to our eventual dismay.
Removed the magnetic drain plug and all my fears were erased as I saw one beautifully amputated gear tooth sitting there.
No other metal at all on the magnet and the oil looked ok (it is four years old, but), just one chunky tooth.
This means the problem IS in the box, not the driveshaft or flywheel/clutch and I'm on the right path to recovery.

I did just realize that our experience putting in the engine last July- the experience I've sorta predicated my time estimates on- is basically useless because back then the engine was stripped bare and now the full intake is on and all those bellhousing bolts are far less accessible than last time.
Oh well.

 

This goes poorly, not well at all.
The replacement gearbox turns out to be a S4 and not the S5 unit it was represented to be.
This was a totally unexpected roadblock but only the first of many.

The initial result of this discrepancy was that my trans crossmember would not bolt on, a bummer but not a total dealbreaker. Then we ran into trouble while replacing the block & centering spring- somehow the shift shaft got totally out of alignment and we could not get back into neutral. So Sigfrid had the brilliant idea that since we were going to remove the tailshaft housing anyway to engage the shifter, why not put my S5 housing back on and then the crossmember would fit.
That actually worked and had the added benefit of my old housing being in pristine condition, with the shifter cavity not filled with dirt and crap. The plastic bush in the block and the centering spring were also fine, so in they went.

Hooray!
After waaaay longer than anticpated, all that remained was to swap out the throwout bearing and put it in.
Aaaand the throwout bearing- which was only installed last July- is bad.
Bearing is fine, one of the "ears" is ripping off.
Neither of us has ever seen this and I can't even imagine how it might happen except for a flaw in the material as the rip is right where the metal was bent during forming. The lever arm and the bearing journal are both in good condition.

I can't find a replacement bearing within 50 miles, which I find rather weird.
Did you know that the S5 throwout bearing (which is apparently the same for turbos and NAs) also covers turbo S4's and ALL RX8's...and even so, no one, not even Mazda, has one.
I guess they are meant to last forever and I'm the only person to ever need this exotic part.
Meh.

Really...double meh, so meh, meh because the replacement unit does not spin as smoothly and easily as the old box, I'm afraid it too is full of crap and I'm going to be pulling it again soon unless flushing it with oil helps.
I'd don't really have any other options at this point but to try it and see.

We idly kicked around the idea of perhaps breaking the old trans down a bit and see how difficult it might be to replace the chipped gear but lacking any knowledge or even the most rudimentary of specialized tools, this seems like a last ditch, Hail Mary option.

I just ordered Rock Auto's highest zoot release bearing option, a SKF unit (and apparently, the last they had in stock, so we'll see how that goes too) but haven't yet gotten shipping info and can't say when it'll show up.

At least it's been cheap so far- even with a $40 bearing I'm only in this for under $75 and some time.

 

IIRC, the gear ratios in the S4 and S5 NA tranys were the same unless you mix in the GTUs trany with the slightly steeper 5th gear ratio. Let us know if the S5 tail housing on the S4 trany ends up not working out and you have to go back to the S4 tail housing. I have a brand new old stock S4 NA cross member (less the two mount bushings) that I picked up by mistake. It has been sitting on the shelf in the garage for a few years now and it's yours for the cost of shipping. Here is a picture of the difference between the two NA cross members for those that have not had the opportunity to stumble across this issue.

 

Thanks so much for the offer, I hope it doesn't come to that but we'll see.

My biggest fear right now is the general condition of this replacement trans, it doesn't spin as nicely as my original and I'm concerned it's full of dirt. When I first saw the trans it was stored outside under a shed roof, sitting on the bellhousing with the wide open tailshaft in the air. The shifter was missing and the shifter cavity was packed with crap.
Swapping in my tailshaft solved the dirty shift cavity and there was no sign of grit in there when we did it, but still...

So, waiting on the throwout bearing might actually be a blessing in disguise.
Advance is selling off Valvolene 80/90 gear oil for $4.50 for a 5 qt. bottle and at that price I'm gonna use it as a solvent/rinse for the new box.
Plan on filling it to the brim, spinning it some, let it soak and then draining before install, hoping the box smooths out and spins nicer.
Maybe it's just dry and a good lube is all it needs.

Or maybe not.
In either case, and despite the fact that I don't think he'll ever see this, I should note that I don't think the seller intentionally deceived me and basically giving me the part absolves him of any guilt.
That said, my good will does not extend to Mazda...oh no, not at all.
Why are the tailshaft housings different between series, why are the crossmembers different?
Why is it so insanely difficult to replace the centering spring?
A simple access port on the other side of the cavity would allow the roll pin to be knocked cleanly through the shaft/shifter block and an extra 3/8" depth behind the block would allow it's removal without going through all that nonsense of rotating the shaft 180° to drop it into the tranny further...a maneuver not even mentioned in the FSM despite it being crucial for success.

I once read that as Honda transitioned from bikes to car manufacture, they made engineers assemble and service the things they'd designed, which lead to many changes for ease of maintenance...a move that Mazda (or anyone, actually) could really benefit from.

 

Mazda added a big vibration damper for the S5's so this needs a bigger tail housing to house it.

and of course they fixed the centering spring too, for the miata. instead of using the hairpin spring, they have a ball and spring inside a new side cover of the shifter case. it probably would retrofit, but i think you'd need the whole set of miata shifter bits.

 

Well, all my warm and fuzzy feelings are gone, replaced by existential dread.
This has turned into a bloody nightmare.

The good news is that I got shipping info on the release bearing...Rock only had one left in stock, which typically means they have ZERO in hand but I guess I lucked out this time.

Decide to tidy up and organize the garage and began by getting the trans as fully assembled as possible, so I started with the VSS (speedo drive).
And could not get the drive gear to mesh and fully seat...spinning the output shaft should engage the gears but it wasn't. Reached into the hole and found that the drive gear just freespins and does nothing.

So the tailshaft housing has to come off again and the gears must be swapped.
This assumes the S5 and S4 speedo drive gears will even interchange and it wouldn't surprise me if they don't.
Because I think Mazda hates me.