gearbox

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vinnie55
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gearbox

Post by vinnie55 »

Anyone got a piazza gearbox?

at the moment I'm considering using a gemini one, I don't know if it can take the thrashing of the turbo motor...

would rather use the real thing if possible
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archangel62
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Post by archangel62 »

Might want to try a WTB on OzGem too. Remember, you'll need a Piazza tailshaft, or an interchangeable spline, since your Piazza tailshaft seems to have a Gemini spline..
Indigo - '76 TX Gemini sedan, G180W+T project,
Abigail - '81 TE sedan, white, G180W ITB project,
New Hotness - TG Gemini drift car, orange, 4ZE1+T
Tardis - 1986 Piazza 4ZC1-T, black, forged, 136rwkw @13psi
Coupe - TX coupe grip car, "do it later", G180W+twin carbs
Trevor aka Jimmy's Gem - Grandpa-spec TD
BA Falcon - Tow car
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Post by Bugle »

Your tailshaft has been converted to Gemini spline already?
Just use a Gemini box, they're basically the same thing as the original, which is why they fail with so much more power than a Gemini. MUA box is the best, but the shifter is a pain to sort out.
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vinnie55
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Post by vinnie55 »

I recon they are the same spline because it was interchangeable with a rodeo gearbox.
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Bugle
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Post by Bugle »

Geminis are either 10 spline or 16 spline. Piazza is 27 spline. There are Rodeos that run 27 spline aswell.
To change the spline you need to get a Gemini universal joint welded to the original shaft, then use a Gemini sliding yoke with the right spline for the gearbox. Gemini auto is 27 spline.
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Post by IZU069 »

Some Piazzas have the old "common" Isuzu universal joints - a 1" diameter bearing-shell from memory; used on Belletts, Wasps, Florians, some Rodeos... and Cortinas and heaps more.
I have one of each in my 2 auto Piazzas (one uses the 1", the other is the bigger Gemini type UJ).

I have every style yoke with the 1", hence can mate any gearbox to my older Belletts, Florians & Wasp. [ The yokes - from memory - older 1" x 10 course spline, Gemini (1") fine spline, larger fine spline, and larger-still fine spline (later Rodeos (MUA); Commodore autos. ]


Though my 400Nm G200W Florian twisted its Gemini gearbox output shaft, I never had problems with the 1" UJs. (But the Amos racing Bellett did - he milled out to take "common" Taxi UJs (in the 1990s?).)
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Post by Bugle »

Is one type rebuildable with clips holding the shells in? The original type on my Piazza has the bearing shells pressed in, and you can't easily remove them, or align them if you could put new shells in. I got another box with 10 spline from a 117 coupe which came with part of the tailshaft which had the same type uni joint as my Piazza, so I couldn't just swap the yoke onto the Piazza tailshaft and had to get a new front tailshaft made with the Gemini joint. The Gemini joint is a standard Holden one though so I don't think they would end up on any jap models.
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Post by IZU069 »

Yes. For the 1" type I have various part numbers: U50, K5L1, K5LGB80R.
They have the outer circlip, and some have provision for a grease nipple (though many wreck them by pumping in too much grease which destroys the seals).

And I suspect I am assuming that the (small) Piazza UJ is the same - I have not removed one and am not sure what measurements I took...


I think all the 117s were course spline outputs (fine spline clutch) - at least for the G200W 117s.
Course were 1" x 10 teeth and were on early Isuzu gearboxes (Bellett, Florian etc) both clutch and prop shaft.
Later the clutch went to fine spline, and later still, the output went fine spline.
After that, the fine spline diameters increased.


And FYI - though the flywheel bearing (spigot) is often a 6203 (40mm OD?), the earlies were 16mmID and later were 17mmID. (There is also a 6203 with a 5/8" ID!).
Measure the diameter of the gearbox input shaft and confirm it matches the flywheel bearing BEFORE you (try) bolting up the gearbox! It's tough enough aligning the bloody box, but trying to get a 17mm shaft into a 16mm hole...!
Actually the same goes for the clutch plate ID and spline type, as well as the ID of the thrust block (to which the clutch thrust bearing is mounted) - there are at least 2 different front gearbox "tube" and block diameters...
And at least 3 different thrust block lengths...
And 2 or 3 different mushroom-bolt diameters (clutch throwout lever pivot)...
And that's just for the Belletts. (With maybe the Florian blocks...)
I knew all that stuff once, though I think I did a post or ten on OzFemini about it.

Oh - and if you use a (4 speed) column shift gearbox, swap the 1st & 2nd and 3rd & 4th gear selector dogs else you'll have an mirrored H-shift (ie, 3&4 to the left; 1&2 to the right) with reverse as normal. (I haven't seen a column-shift 5 speed.)


Finally, cut&shut prop shafts shouldn't cost to much. I had to cut ~1" (~25mm) off a Florian tailshaft for G200W & Gemini 5 speed (0.785 5th ratio) conversion. It was cut & shut, new UJs (which I supplied) fitted, and balanced for ~$120 circa 1997. (Turns out the 1" cut was unnecessary - it was an output spline problem!.)
Anyhow, I was considering cut&shuts to use the bigger GM/Gemini & Piazza/Rodeo/Jackaroo UJs...
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Post by archangel62 »

Basically, I slipped a Gemini manual fine spline tailshaft into the back of his gbox! Straight out of one of my 5spds! Heh - so AFAIK his is a Gemini box, or has had the guts converted.

However, it already runs the push type clutch - obviously, to integrate with the hydraulic release system.

So I'm trying to figure out the easiest way to transpose a Gemini 5spd into his Piazza - if he can just swap stuff between his dud converted Gemini(?) box over onto a new Gemini box externally (ie change clutch fork and pivot, rear xmember and shifter) or if he has to actually pull apart the gearbox and change gearsets or assemblies. I've never really pulled down a gearbox before (yet).
Indigo - '76 TX Gemini sedan, G180W+T project,
Abigail - '81 TE sedan, white, G180W ITB project,
New Hotness - TG Gemini drift car, orange, 4ZE1+T
Tardis - 1986 Piazza 4ZC1-T, black, forged, 136rwkw @13psi
Coupe - TX coupe grip car, "do it later", G180W+twin carbs
Trevor aka Jimmy's Gem - Grandpa-spec TD
BA Falcon - Tow car
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Post by Bugle »

Yeah the clutch is the only thing to sort out. They modified the drive gear bearing retainer casting for the Piazza box to provide a hole to screw in the pivot ball for the push clutch fork. All you have to do is swap the bearing retainer off the box that is currently in the car onto another Gemini box.

Another thing is with the Gemini gearbox the rear part of the case has those two remote shifter mounting holes offset further backwards, so only one of the screws will line up, but I ran mine like that and it was alright.
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Post by IZU069 »

Check the clutch fork angle BEFORE mounting in the car. (That assumes an engine to check on.)
If the pivot/mushroom bolt or thrust-bearing block lengths are wrong, you won't be able to use the clutch...
I think the correct angle is about 85° (pointing forward; angle relative to car axis - ie, the prop or gearbox shafts - not the bell housing), but somewhere around 90° - not pointing more than (say) 20° or 30° forward or rearward from the 90° perpendicular. Apart from push-forks sliding off the mushroom pivot if pointed forwards enough, you probably won't fit the fork push-rod. If pointing too far rearwards, the fork will hit the body. All the fork mechanisms are designed for near perpendicular operation.


Many of those front gearbox (bearing) plates have holes for either type though a few may need tapping. Others usually at least have the casting for "the other" clutch fork.

Though I fitted a Gemini fork with cable, never again. I'll stick to the existing mechanical push type on Belletts & Florians, else convert to hydraulic.
Apart from the complexity of fitting the cable, they break too easily - albeit using a heavy duty Rodeo clutch & pressure plate (for the G200W).
IMO - hydraulic is best. And they can be geared for heavier clutches if needed (ie, increase slave cylinder diameter).


Remote shifters - again something I once knew. (Was it the Rodeo etc 5-speed's with (pre 4ZE1 MUA) alloy-encased linkages that was the same length as GT Belletts? Piazza was longer (and too wide or my vehicles) and I presume did NOT suit the Geminis (they had to be chopped; and maybe narrower? Hmmm - wonder if the GT Bellett shifter (hence Rodeo alloy) suits the Gems? The standard shift is in the same position.)
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vinnie55
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Post by vinnie55 »

yeah that's pretty much it

-bugle, yes only one hole lined up on the broken gearbox. It should be fairly easy to copy it all over.
I just have to find another gemini box now and hope it can take the MASSIVE POWER of the superior piazza engine :)
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