MUA-5 Transmission Swap.

[Bugle]

I beat up my tunnel a bit, seems the tunnel goes high then slopes down slighty as it goes toward the firewall, so I had to beat it up at the front to make it more horizontal where the shifter goes. Making the clearance on the left side was easy enough. This creates 2 problems above. There's a mount ontop of the tunnel there where the centre console mounting bracket attaches, so that needs to be modified so the mounting holes are 10mm higher. The other thing is that it pushes up the vent pipes that go from the heater box to the rear passenger feet. There's a small 90 degree duct that attaches to the heater box and then to those pipes which needs to be modified. I forgot to take a photo but part 21 in this drawing is the duct, and the bracket in the middle of the dash in the second drawing is the metal bracket.







Need to get some new flywheel bolts and I can reinstall it, ended up with a 4ZE1 flywheel and clutch now.

[ImpulseRocket89]

I bought my MUA box a few weeks ago with the alloy quadrant shifter, so I'll be following impulserocket's lead with putting the Piazza quadrant on a machined angled surface, and then adding a sports shifter to top it off. I'll be looking at this thread very closely when the time comes. Excellent write-ups by impulserocket, followed by bugle. All of the guess work has been eliminated.

I am actually following Bugles lead with the shifter and building my own bracket and modifying the alloy quadrant to accept it.

I think a good compromise to this would be to use the factory angled quadrant and have the housing machined, but try to remove all of the rubber bits from the impulse shifter bracket/mounts. This should take a good majority of the slop out of the system. Then you could still modify/create your own shifter (such as the T5 unit I posted or Bugles setup) to mount to the bracket.

This would prevent you from having to hammer out the trans tunnel and running into other problems.

Bugle, if you get a chance, could you take a picture of the bracket you are talking about. I am confused as to why the console mounting bracket has to be modified to make the mount points higher.

I assume you are talking about re-drilling the holes so that the whole console/heater box shifts up a little bit, thus clearing the tunnel.

As far as the foot heater part goes, I will have to discover if that is a similar issue for those of us with LHD cars, or if there is some other problem that will arise from it.

[Piazza_man]

Rubbers. Gotchya. I would have thought the rubbers were important to reduce engine/gearbox vibration. Thanks.

[Bugle]

Depends what you prefer, i'd rather the shifter feels solid and clicky, rather than feeling like i'm shifting a FWD car cable shifter. Although the linkage bushes were a bit worn out on my original one which would've contributed to it.

Will get some pics of the interior bits.

[Bugle]

This is the dash and centre console mounting bracket, it needs the lower mounting holes moved further up, either by cutting the bottom of it then flattening the bottom edges of those holes in the middle of it and redrilling the mounting holes, or by cut and shut welding.


This is the heater box and the rear foot ducts with the joining duct not installed.
There is some thick sound deadener on the tunnel underneath the pipes which can be removed to help lower them a bit, I haven't removed it yet.

[IZU069]

I would have thought the rubbers were important to reduce engine/gearbox vibration. Thanks.

Vibration? In an Isuzu? Well, at least not since I changed my front wheel bearings last week LOL. (I thought it was my newly machined drums! If it was solely the bearings - a bad vibration around 84kmh - I can only state how glad I was to replace them before a major disaster! BTW - that's my Wasp, not a Piazza.)

But FYI - all my gearsticks have been a rigid mount whether direct or via alloy extensions (ie GT Belletts - similar to the MUA extension gearshift) and vibration has IMO never been a problem. (However being belted in the knee by the Wasp's solid gearstick knob under conditions of duress has been an major issue!)


Also FYI - I'm currently fitting a Piazza hydraulic clutch assembly to the Wasp.
I had to make a bracket to move the engine to gearbox/slave-cylinder cast-iron bracket 25mm higher than the matching bolt holes at the bottom of the G161 OHV block. (I'm using n MSG Rodeo box with twincam type LHS-starter bell housing).
It is otherwise a straight forward refit except that the G-OHV alloy sump casting (the same as most G161Ws) includes the engine to lower gearbox bracketing so that has to be cut/ground away to fit the Piazza/4ZEx bracket, and the Wasp (like Chevy LUVs, KBs and early Rodeos) has a torsion bar that gets in the way. But now I am an accomplished alloy sump cold-chiseler.
Interesting though that the 4Z and MUA gearbox save cylinders are 25mm lower... (But aren't the Piazza and pre-4ZE1 gearboxes MSGs? Am I confused again re MSA, MSB, MSG, MUA boxes, or have I never compared their clutch-lever positions? Hang on, I do now recall lower RHS lever pivot position... My G161U & G200W MUA fitting will be interesting...)

[Bugle]

Maybe the older boxes never ran hydraulic clutches as standard so they never had to worry about slave cyl mounting and those holes being equal distances from the fork?

[ImpulseRocket89]

Thanks for the pics on that lower mount position. That makes a lot of sense, and honestly isn't that difficult of a fix. Looks like a simple re-drill should work ok.

As far as slave cylinder differences. I decided to go with a Rodeo slave on my car. The Clutch MC pistons sizes are the same between both and the Rodeo unit mounts right to the box in a similar location. I think Ludacris2.0 used the factory Slave, which is why he had to dremel down the mating surface a little bit to make it work. I have noticed that the MUA bellhousing flange is a little bit thicker than the factory MSG, which probably threw off the distance enough to cause it to bind or not mount up properly.

I guess if all else fails I can simply use an Impulse slave and do a little sanding, but I am extremely confident that the Rodeo unit will work.

[IZU069]

Maybe the older boxes never ran hydraulic clutches as standard so they never had to worry about slave cyl mounting and those holes being equal distances from the fork?

Being "Gemini", I suspect the early Piazzas were cable. I have an I-TEC G200W (Jap else NZ Piazza) whose gearbox has a bracket for a cable from the typical traditional "two horizontal holes" as on Geminis and used for Bellett/Florian mechanical clutch linkages. That bracket has the perfect cable height for my clutch throwout lever.

My Piazza hydraulic set up came from Mick Esq. (Legend! From central NSW as I recall) for my auto to manual conversion. (Unfortunately both of my Piazzas are autos.)

Alas my GMH Piazza Sparts books are buried somewhere and I can't recall whether cable or hydraulics from my workings on Bartamann's nor Cary's manual Piazzas, nor my pedal box from RodeoBob, though I reckon they were all hydraulic.
But I have pics of hydraulics on LHS & RHS 4ZC1-t models, but I have no idea when the change from cable occurred. (I would have thought all 4Z Piazzas to have hydraulic clutches.)

The Piazza hydraulics look the same as on my UBS17 4ZE1 Jackaroo except the Jack has an intermediary junction box on the left engine bay. (Hence the "direct" Piazza plumbing is more desirable for my use.)

The Piazza master is common 5/8" (15.87mm) bore and the slave is a 7/8" (22.23mm) bore. This arvo I should find out if its seals are common and maybe the same as certain Jackaroos & Rodeos.

I also have a physically similar Mistubishi Magna master cylinder (1996 TE; 5/8" bore; its slave is 13/16" = 20.64 mm) though that uses the smaller diameter and more common outlet thread as used on most Jap brakes. (Isuzu seemed to stick with larger pipe size for their clutches - eg, 1965 Wasp, 1986 Piazza, 1990 Jackaroo.)
And some Mitsubishi (and other) slaves look compatible to Isuzu's "horizontal gearbox 2 hole" slaves, but I may confirm that at a later date (for direct mechanical to hydraulic Bellett & Florian conversions as well as a Wasp replacement).

Alas I have to exchange both master and slave as the Wasp uses much larger 7/8" master with 1" slave, hence the Piazza & Mitsubishi 5/8" master cylinders only yield half the required travel with the Wasp's 1" slave.


And sorry for any hijacking due to my replies. They should be a separate thread (eventually?) but although specific to my Wasp conversion, it may be of Piazza interest - ie, the ability to use Rodeo/Jackaroo (and maybe even re-plumbed Mitsubishi) master cylinders, and Rodeo/Jackaroo slaves, or alternate "2 gearbox bolt" slaves if the gearbox has those holes.
I am looking at it from the POV of a universal hydraulic clutch for all my Isuzus (mainly Belletts & Florians) for any engine (mainly G161-OHVs & G200Ws) and gearboxes (including MUAs).
And I prefer hydraulics. I tried a Gemini cable set up and found I preferred the (yech!)older Bellett/Florian mechanical linkage set up.

And as usual, I marvel at Isuzu's inter-model parts compatibility. The later reduction starter motor and pre-4ZE1 (pre-1989) Jackaroo and Rodeo LSD into my Wasp and Florians has been a godsend (albeit the Florian needs the Piazza's 3.9:1 crown and pinion else the Piazza LSD if the 4.55:1 ratio is undesirable. And the use of Gemini and Rodeo gearboxes behind traditional OHVs and the GW twincams is well known.
And now to find the same 4Z block's rear engine-gearbox bracket (with clutch slave cylinder) holes the same as the 5-bearing (G150?) and G161 OHV (and hence GW twincam blocks, and I suspect G-Z) block holes is yet another bonus. As to the different slave cylinder heights of 25mm, I'll solve that later...

[Bugle]

Yeah Australian Piazzas are hydraulic, not sure when Japan changed over but i've seen photos of G200 Piazzas with cables. However US G200Z impulses were hydraulic. I assume this is because the clutch pedal is in the right place to mount the master cylinder on LHD models. Then they later figured out that shaft arrangement for RHD models.

I'm not sure yet if the MSG slave cylinder will work on the MUA, the gearbox is thicker at those holes on the MSG, so the MSG slave cylinder will be sitting further toward the front of the car when mounted on the MUA gearbox and might push the piston out too far. I can machine some spacers easily enough but new MUA slave cylinders are cheap anyway.

[ImpulseRocket89]

From what I understand (previous post says this) the Impulse slave does work, but you have to remove material from the bell flange for it to mount up properly. That is why I am simply using the slave from the (RWD) Rodeo. I was mistaken on the Slave piston size, I guess the Impulse slave is 1/16th" bigger in diameter, so I am unsure if that will have any adverse effects. I can't imagine it being too severe.

If all else fails, I will make the Impulse unit work.

[Bugle]

It's the other way around, there's less material on the MUA gearbox so you need spacers between the slave cyl and bellhousing to get the original slave mounted in the right spot, i've forgotten the exact difference but I think it was around 10mm. Could just be the same slave cylinder with a longer pushrod for the MUA.

[IZU069]

I'll probably get to figure out all the above in my "universal Isuzu" clutch quest (maybe sometime before next century??).

I can confirm having to remove a minor protrusion from the MSG bell flange (and G161U engine backing plate) for the Piazza slave to sit in properly. It's the equivalent of a ~10mm triangular protrusion.


Having just sourced my new seals I'm about to fit the lot.

FYI - the master seals were from a PBR K7716X kit which is for Toyota Coronas (RT 104/118 3/77 - 9/79 & XT Starfire engined 10/79 - 12/80). Their numbers were P6968 & P7076. [ Though I had to replace the P6968 after ripping it. This is the first time I have ever needed a vice to refit brake and clutch seals! ]
And the new slave seal I have is marked "KSG 227R 5/8H ANJ22 12".
But I have catalogs with kit numbers for the Piazza and Rodeo etc brakes and clutches and I intend to tabulate them (and whatever other vehicles they match).
And I'll also compare and tabulate my 1989 4ZE1 UBS17 Jackaroo/Trooper since it has a very similar looking setup.


ImpulseRocket - a difference of 1/16" diameter to the Piazza 7/8" slave means ~15% travel difference (it's the diameter ratio squared).
IE, a 13/16" piston will travel ~15% further than a 7/8" = 14/16" piston. [13/14 = .928; .928 x .928 = .86; ie, 86%, ie, ~14% difference]


At this stage I expect the MUA clutch hydraulics to be a good replacement for the Piazza - ie, the master and slave look physically the same with the same threads. If so it's merely a question of the diameter ratios, rod lengths and mounting.
I've bored out the threaded Piazza mounting studs to slip over the Bellett/Wasp/Florian pedal box studs. And I'm using the longer Wasp slave rod. The (short!) Wasp pedal rod is still TBD.

[Bugle]

I've finished the final fitment of the gearbox.

Went with a 4ZE1 flywheel and clutch. This also requires a 4ZE1 starter motor to be used due to the flywheel being the same diameter as the ring gear the original starter housing won't clear it.

Flywheel comparison


Mounted it using 4ZE1 flywheel bolts, these are the same threads as 4ZC1 bolts except they have a large flange on the head, are stronger grade 12 vs 11, and are still available through Holden.



Got a clutch industries 4Terrain heavy duty clutch. Weird thing with button on one side and full face on the other.




Went in fine, now have 8mm clearance above the gearbox before it hits anything.


Shifter in the right spot


Had to get shorter shank bolts for the slave cylinder to account for the thinner mounts on the MUA, the original slave cylinder works ok except mine is leaking so i'm just going to get a new 4ZE1 one. The manual says the original slave cylinder is 13/16", i'll find out what it actually is when I remove it. Apparently the 4ZE1 one is 7/8".



Starter motor fits fine except that the lower mounting hole on the MUA gearbox appears to be M10x1.5 thread instead of M10x1.25 on everything else.




If anyone is going with the original 4ZC1 clutch something I noticed with it before I removed the gearbox after test fitting was that the throwout fork was at the wrong angle, instead of being perpendicular to the input shaft it was pushed back almost as far as it could go. The pivot point must be in a different spot on the MSG and MUA which means that you can't use the MSG throwout bearing carrier. Pretty sure you would need to take the MUA carrier and machine it down to fit the MSG throwout bearing.

[ImpulseRocket89]

I've finished the final fitment of the gearbox.

Went with a 4ZE1 flywheel and clutch. This also requires a 4ZE1 starter motor to be used due to the flywheel being the same diameter as the ring gear the original starter housing won't clear it.

Had to get shorter shank bolts for the slave cylinder to account for the thinner mounts on the MUA, the original slave cylinder works ok except mine is leaking so i'm just going to get a new 4ZE1 one. The manual says the original slave cylinder is 13/16", i'll find out what it actually is when I remove it. Apparently the 4ZE1 one is 7/8".

Beautiful looking stuff. All clean and shiny looking.

Thank you for the information on the starter. I had actually held off ordering a new starter because I was unsure of that very issue, so that definitely saved me some time and headches.

The factory Piazza/Impulse slave is a 13/16". I just got a brand new one in the mail a couple of days ago. The 4ZE1 units are 7/8" as well. From what I can tell without placing them side by side, they appear exactly the same on the outside. So, I think either would work just fine.