Piazza Diff Ratio alternatives

andrew · Post by **andrew** » Fri Mar 31, 2006 9:14 am

I have a Piazza rear axle from a non-turbo model in my Chevette rally car. I want a lower ratio than the Piazza 3.9:1, say about 4.6:1. Is there any other Isuzu crown wheel and pinion that bolts straight in?
What if I change to the turbo rear axle, is this beefier and are there crown wheel and pinion options for this axle? Does the LSD unit from the turbo bolt directly into the non-turbo axle?
I will greatly appreciate learning from those who have already had the trials and tribulations. Thanks

GeminiCoupe · Post by **GeminiCoupe** » Fri Mar 31, 2006 3:07 pm

There are two types of Piazza rear end - the torque tube type and the 4link rear. I dont know much about the torque tube type, pretty sure its fitted to all of the non turbos and some of the early turbo models also got it with an LSD centre. Not sure if there was a difference in axles, but the ratios was the same and i daresay the centres interchangeable.

The 4link rear as fitted to aus-spec Piazzas was turbo-only, and to my knowledge IS stronger however it needs modifications to fit in a Chevette. Im guessing this type isnt the one in your car. If it is, ask Rodeobob as he knows abit about these and said something about items being interchangeable with the Shuttle/WFR van, early KB Rodeos etc.

Nick-

Rodeobob · Post by **Rodeobob** » Fri Mar 31, 2006 3:09 pm

Depends which diff youve got. If its from a torque tube Piazza your stuck with it.

Bob.

Post by **wedgenut** » Fri Mar 31, 2006 4:18 pm

Wecome Andrew to our happy little band, even if you only have a little bit of a Piazza. All models released in NZ were non turbo and had the TT diff, very very few would have had LSD. Private used import turbos also have the TT rear and again LSD not that common and they were never fitted to automatic cars either as far as i know. JDM models up to 1988 certainly have TT rear end but UK ,US impulse releasse were same as OZ I THINK!

The AUS diff is quite different in that it has a removeable diff head assembly in a plain banjo beam. The TT rear has the crown wheel and carrier bolted into the banjo from the rear and the pinion is set up directly into the nose of the banjo housing so not even nearly interchangeable.

I am interested in what youi have so stick a cvamera under the back and give us a quick look at what you actually have as i would have thought the Piazza tt rear end would have been a trick to fit a chevette.

Post by **wedgenut** » Fri Mar 31, 2006 4:24 pm

Andrew
Forgot to say, have you checked the ratio physically as my specs say 3.5 for RHD and 3.9 for LHD although it is possible that JDM's imported here have a 3.9. I confess I have not checked any of mine I just drive em

Bugle · Post by **Bugle** » Fri Mar 31, 2006 8:35 pm

It's 3.583 for G200Z ones and 3.909 for G200W.
Yeah and the only Isuzus that used that type of housing was the Gemini and Piazza, all other Isuzu diffs seem to be banjos. So if you've got a 5-link you can get silly ratios like 4.5:1 from Shuttles and Rodeos.

Tommy · Post by **Tommy** » Sat Apr 01, 2006 4:30 am

If this is the 3-Link, then a lot of Opels during the 70's and early 80's had the same rear end, and parts made for use in rallying can be found, but they aren't cheap.

Tommy

madmike · Post by **madmike** » Sat Apr 01, 2006 6:04 am

hi andrew u wouldnt be the bloke off trademe would u???

just a little tip a guy down here who races a chevette has actually put in a gemini diff int his and got a guy from aus to fit in a lsd unit bit pricey but works great!!
what motor are u running

i started with a chevette bought the piazza for a retro fit and fell in love with it the rest is history

so ive got shit loads of chevette parts sittin here if u want any

andrew · Post by **andrew** » Mon Apr 03, 2006 6:23 pm

Thanks guys for your responses. It appears I have an 8 bolt torque tube axle for which I cannot get alternative ratios, BUT I can get a Quaife ATB LSD to fit. Alternatively I go to the turbo 10 bolt diff for which i may find Jackaroo or similar crown wheel and pinion to fit, but the Isuzu LSD unit for these are like rocking horse sh..t. Or I dump it all and get something else. You guys were supposed to make this easier for me!!!!!!!!.

For those who have asked we have 4-linked this axle, dumped the torque tube, dumped the spring pan and put coil-overs behind the axle in vertical turrets. Diff is definitely 3.909:1. I will try and upload some pics. Still got an HS body kit to fit

Http://www.holdenpiazza.com/puplic/images/66203480.jpg[/img]Http://www.holdenpiazza.com/puplic/images/54339462.jpg[/img]

Good photos of my jack!

Tommy · Post by **Tommy** » Mon Apr 03, 2006 7:17 pm

You can get alternative ratios for that diff, but they are like 1000 AUD each, also there are LSD's available, but they have been out off production for a long time and most that have one don't whana lett them go, or want to much if they lett it go.

Tommy

Post by **wedgenut** » Mon Apr 03, 2006 8:42 pm

Looks like you got the skills and facilities to do what you need to do so maybe you need to look further afield. To be honest Piazza LSD's are as rare as a sober australian with a job and those that have them are likely to hang on to them. Piazzas are hard on diffs when driven properly, ask my missus who blew one to bits whlile out on a "Sunday Drive" She claims it "just sorta happened" but I know the truth, the mad bitch was playing silly buggers with a bloke in a rotor with his hat on backwards. She should know better but this is the broad that used to wheel around in an RS200 as a shopping cart!

Bugle · Post by **Bugle** » Tue Apr 04, 2006 2:31 am

Didn't Rodeos and Jackaroos come with LSD's at all? I would have thought they would all have them, to help get over big things, mainly sheep if in New Zealand.

Rodeobob · Post by **Rodeobob** » Tue Apr 04, 2006 4:28 am

Depends on how wide you want the diff to be.
You could fit in anything if your prepared to shorten it.

Heres a tip. All jackaroos form 81 to 84 have LSD's in em.
85+ when the 2.3L motor came out it was an option.
To date i havent found a pre 84 without an LSD. Not that ive looked at heaps.
Your pretty much limited to one ratio and thats 4.777.
Its possible some diesel Jackaroos were 4.555 as were some Rodeos.
The 4 speed C223 diesel 2x4 Rodeo was 4.1
The 4.777 is the comon one as far as i can work out.

I dont think the motor will mind a nice low gear. What is it????
Seeing as its not a strictly Isuzu car you could look elsewhere for a diff.

What you going to do about the stud pattern????
The rodeo/jackaroo diff should be close to the right width,
if i get a chance tomorrow i will put a tape on one.

And for the Piazza gang, ive got no idea if the 3.9 gears will go on a Jackaroo centre.

P.S. if you keep hittin return when you type its easier to read. Yeah im lazy.

Cheers Bob.

andrew · Post by **andrew** » Tue Apr 04, 2006 5:29 am

Question for Tommy, can you please give me a contact for the crown wheel and pinion, I would like to look into that option further.

The reason we chose Piazza components was at the front they bolt straight on, have the same stud pattern, and vented rotors, at the rear we get disc brakes with no great modification, and to set the rear up the two Piazza links bolted right into the Chevette link boxes, which held the axle square while we fabricated the 4-link.

Could go to all sorts of other diffs, but then we face the stud pattern, disc brake etc issues and this way it is at least from the same 'family'.

Tommy · Post by **Tommy** » Tue Apr 04, 2006 6:05 am

http://www.enem.se/produkt.asp?r=25

What you'r looking for is:

"slutvaksel" (finaldrive) for the Asc/Man/Kad and

"diffbroms" (LSD) for Asc/Man

The prises are in SEK Swedich Kronor 1000SEK = 180AUD at the moment.

Tommy

By the way, they have good prices on Autorotor and Lysholm compressors