Piazza_man project

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Piazza_man
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Post by Piazza_man »

After talking to the technician and seeing the box again in front of me this morning I now understand what you're talking about Bugle re your 4th gear comment. 4th gear is a lay-man's term used to describe this gear simply because it physically has teeth (like the other gears). However a gear that is directly connected to the input shaft and is constantly engaged whilst the vehicle is moving set's it apart from the rest of the synchro gears. I understand the input shaft gear/4th gear is literally a one-piece casting of the input shaft now, but I also understand that it is a still gear with teeth and is more loosly termed 4th gear. Your comments are scientifically spot on. In lay-speak that cog is co-incidentally termed 4th gear thanks to the 1:1 gear ratio (as most if not all 4th gear ratios are 1:1). Man I learnt so much about this MSG box (which doesn't automatically mean I know everything about boxes btw. Still have a lot to learn).

Bugle you're right about damage to the counter shaft (cluster gear). I mustn't have been listening to the technician the first time. Whilst the 4th gear (or input gear drive if you will) suffered excessive wear the corresponding gear only showed signs of excessive scuff marks. It's the level of scuffing that causes gearbox whining that you hear in the cockpit. The more the scuffing the louder the whine. Interestingly I discovered that while 4th cluster gear is excessivly scuffed you will only hear the whining in 1st, 2nd, 3rd, and 5th gears only, but not in actual 4th. I believe it has to do with the distribution of force on the cluster gear.

Anyway I hope I haven't confused anybody here. The point is I'll need another input shaft and corresponding cluster gear (counter gear in Bugle speak LOL).
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Post by Piazza_man »

Oh and I appreciate your comments too Wedge. A credit to your diplomacy and thoughtfulness mate.
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Post by Bugle »

Yeah stuffing the cluster gears makes the box a throw away really. Isuzu will want too much $ for the shafts. I enquired about that about 10 years ago when I stripped some teeth of 2nd gear and it was going to cost thousands.

It's quiet in 4th because those gears on the cluster aren't transmitting any power. If you want your box to last forever just use 4th gear all the time, the clutch might not like 4th gear starts though!

I think the path of transmission it's best demonstrated ms paint style

1st
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2nd
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3rd
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4th
Image

5th
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reverse (direction reversing idler gear not visible in pic)
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Post by Piazza_man »

Exactly right with the diagrams Bugle. Btw have you had a chance to look at that link. I figure you would know a lot more about what is compatible to suit the 5H box. As time goes by I haven't heard back from them. Maybe the email went straight into their spam boxand never actually reached anybody. Who knows.

Perhaps of interest to some the MSG-5H box is also used right up to the JDM '89 HBL Piazzas as well. From '84.5 to and including the '88 JDM Irmscher MSG-5N boxes were used. From '81.5 to '83 JDM Piazzas used a MSG-5X box.

Each 5(?) designation had subtle differences in 1st, 2nd, 3rd and 5th gear ratios, but I don't know if the input shafts with their 4th gear cogs share the same diameters and teeth numbers as the 5H. I would presume the input shafts would be the same to save on expensive tooling costs, but I can't be sure unless I get a response from my email. Is the input shaft from a 2WD 4ZD1 Rodeo identical to the Piazza input shaft? If this is all true then the only unique item to source would be the cluster gear because of the 5H ratios.
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Post by Bugle »

Yeah it would make sense to try and keep the input shaft gear the same on every transmission to save costs, but Isuzu don't always make sense.

It's likely that the KB MUA-5C 1st and 2nd ratios are the same as the Piazza and there was a typo somewhere along the line because they are so close. 5th gear is removable from the cluster gear shaft so the shaft and everything else apart from the two gears on 5th might be the same between 5C and 5H boxes. That site doesn't list an MUA-5C either though.
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Post by Piazza_man »

Yeah I've seen that typo somewhere before. I think it may have started from Rodeobob's link. I might send another email to them. I know I know. I'm a persistent barstad but if I can locate a supplier for replacement parts like the input shaft and cluster gear then all forum members with manual trans could benefit. I might ask on the 'zone' to see who they use.
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Post by IZU069 »

Bugle wrote:It's quiet in 4th because those gears on the cluster aren't transmitting any power.
If it's the main-shafts roller bearing or the bearing's hardened shaft surfaces that is stuffed and noisy, the box will be noisy anytime the engine is running unless it's in 4th gear (1:1) or the clutch is in (disengaged) - that 's the only time the mainshaft halves match speed.
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Post by Piazza_man »

IZU069 wrote:
Bugle wrote:It's quiet in 4th because those gears on the cluster aren't transmitting any power.
If it's the main-shafts roller bearing or the bearing's hardened shaft surfaces that is stuffed and noisy, the box will be noisy anytime the engine is running unless it's in 4th gear (1:1) or the clutch is in (disengaged) - that 's the only time the mainshaft halves match speed.
Well the transmission was put back in the car the other day. It was spare tranny that I picked up off Dave that was serviced. It was found to be in better overall condition than the original one (which had done almost 3times more kms). Peter you were probably right re the main shaft roller bearing being noisy. The pic below is is the bearing that sleeves over the input shaft which is then jammed into the main shaft:
Image
The pic shows the surfaces of the hardened roller bearings are starting to break down, and this came off the 2nd newer box which had done about 100,000kms. This surely would have been a culprit for noise. Of course this and all other bearings were replaced. The input shaft that this bearing was seated on was machined and a new hardened sleeve was put on. Good as new now. On top of that the input shaft gear (4th) and the corresponding cluster gear were lightly sand blasted to remove scuff marks. It was an experiment to see if the gearbox whine could be totally eliminated. We shall see.
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Post by Piazza_man »

Have some good news re rear end replacement nolathane bushes. After much researching I have sourced a bunch of nolathane bushes to replace the upper and lower links. The bushes are actually designed for other vehicles, but I'll go through all that in another post. Basically what it means is that the upper link nolathane bushes won't need any modification work. The lower links will only require some slight work to make them fit, but it will be the best outcome if you don't want to turn individual bushes on a lathe from scratch. The modification that I speak about will be piss easy to do, and I'll go through everything once the bushes are fitted to my car this week. I just need to make sure everything will be a nice fit and no nasty surprises.
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Post by IZU069 »

A bit late, and I'm not sure if I said it earlier... But I have a document in which I listed various Isuzu gearbox ratios.

It was originally for my Belletts & Florians using Gemini gearboxes.
I was interested in the ratios - mainly a reasonable 1st gear (depending on hill-climb & rally versus "GT" specs) and the long 5th gear (0.782 as opposed to the typical 0.855).

Though I have a copy, it may not be the latest.
[ FYI: My new 2-week old i5 Windows7 PC has finally replaced my P4 Windoze 2000, but I still haven't bothered with certain data recoveries...
The gearbox file started as an engine & gearbox file (bores, strokes, ratios) and ten split into a gearbox file which added diff ratios, speedo gearing, clutch dimensions, etc for any suitable G-series substitution - eg, diesel & 4Z series engines.
Being cross referenced and version controlled, its "accurate" recovery may be problematic... (I want the source info - there were so many contradictory sources!). ]

To think that now I'd have to review what the MSA, MSB, MSG & MUA versions were (maybe MSA = non-sync 1st MSB; MSB = "one piece" 4-speed Bellett/Florian etc; MSG = 2 piece Gemini & Gemini DOHC, Piazza, mid Rodeo etc; MSG = 4ZE1??
But the common ratios were 1.989 2nd; 1.356 3rd (and 1:1 4th) as per the Bellett GT, ZZR, Gemini, Piazza, etc.
1st gears varied from 3.207 (GT) to 3.174 & 3.431 (Piazza) & 4.449 (Wasp).
5ths were 0.782 (early Gemini), 0.775 (Piazza), 0.809 (Mu) with most Gemini & others being 0.885.
(Reverses from 3.402 Piazza to high-3's Gemini etc; 4.9 Belletts, 5.9 Wasps.)


Piazza except DOHC can use the Gemini & G-Z series boxes. But with the appropriate bell housing swap, any G-series can be used - ie, OHV, Jap SOHC, DOHC etc had a left-side starter.
Then there is the 4Z series (RHS starters) which I think can also be used EXCEPT the 4ZE1 which has a larger bell etc (I got interrupted during that investigation).

The snag is the plethora of clutch throwout-arm types (push or pull) and their mushroom pivot lengths; thrust-bearing block IDs and lengths; and input and output shaft variations (16mm & 17mm inputs, 3 output diameters, course & fine splines). So too the prop-shaft lengths (only if changing from 4 to 5 speed - irrelevant for us) and gear shifts and sticks. WARNING - always get the stick etc with the box! To a lesser extent, so too the clutch thrust bearing block.)
But most can be overcome...

And there are 2 input-bearing versions - the earlier layshaft needle bearing (with smaller alloy front cover) and later and stronger ball bearing (larger cast cover), but the needle can be upgraded to the ball with the later front cover and bearing-hole enlargement.

And all shaft splines are available with the 1" removable universal joints, though these days IMO driveshaft cut&shuts with balancing are not a bad nor costly idea.


My last investigation was for a 4ZE1 box behind my G200Ws in Belletts, Wasps & Florians (since I kept bending output shafts) - preferably with the Mu box for its ratios (3.783 1st, 2.246 & 2.314 2nd, 0.809 5th).


Maybe I should prioritise some data recovery?
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Post by Piazza_man »

Thanks for your input IZU. All these variations in ratios, splines, cluster gears and teeth numbers pretty much ensures nothing is interchangeable.
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Post by IZU069 »

Though if shaft sizes are the same, and BOTH gears replaceable...

But I replaced gearboxes instead. Synchro rings and bearings was my limit.
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Post by Piazza_man »

If I found an input shaft with the same size spline and 4th gear teeth as the 5H then that would be a start.
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Post by Piazza_man »

While I'm still waiting for the suspension bushes to be replaced I decided to tackle the front badge. I went for an updated look but to pull this off it meant I still had to use the original badge for it's rear lugs. The front raised ISUZU face of the original badge got lopped off with a hacksaw so as to sit snugly behind the new badge.
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The back shows 2 pop rivets to attach the 2 badges together.
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Post by ImpulseRocket89 »

Wow, I missed a lot from not paying attention to this site for a year. Beautiful work with the car. I will probably be messaging you a lot when I get to the restoration/body work side of things.

I know I will be messaging you in the future about the seat mods, at 6'5'' (195.6CM) tall, room has always been an issue for me in these cars as well.
1988 Isuzu Impulse Turbo.
2005 Ford Crown Victoria LX

RIP 1989 Impulse Turbo, aka "Rakete"
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