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Info needed about the M76 5 Speed Gearbox


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#1 _sstorana_

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Posted 24 January 2010 - 08:36 PM

Hi All

well after yesterday's run along the freeway, I have come to the realisation that the Sunbird needs a 5 Speed Gearbox!!

You see, with the 3.90:1 Diff and the MC6 4 Speed, at 110kph it's running at 4000 rpm which is a little high, and very noisy(can't hear the AM radio talkback) :rockon:

I have had a look in the books and it seems that Holden had a 5 speed gearbox (M76) behind the old starfire in the VH Commodore.

If anyone has had any dealings with this box, or can give me an idea if it is a straight swap into the UC, that would be appreciated..

if anyone knows of one around Sydney to NEwcastle, that might be handy as well..

cheers
Mick

#2 76lxhatch

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Posted 25 January 2010 - 05:31 AM

They were used behind the VK Starfire and EST sixes as well, I gave one hell for a couple of years behind a fairly standard black carbed six with no problems. Its not a bad box to drive either.

It should be a straight swap into the UC as long as the shifter position lines up (no reason why it wouldn't), people put them into a lot of earlier Holdens with sixes. As I understand it they're not up to a lot of power though.

edit - I have a book right here, gear ratios:
First 3.23
Second 1.97
Third 1.26
Fourth 1
Fifth 0.79

Edited by 76lxhatch, 25 January 2010 - 05:36 AM.


#3 _sstorana_

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Posted 25 January 2010 - 11:13 AM

Yeah, I knew that they were also in the VK so I do have a couple of options there as well. As for power, it's not going to be a factor unless I do some serious work to the Starfire!! :burnout:

I did notice that the VH and VK boxes have different ratios in them..

VH M76 gear ratios:
First 3.65
Second 2.14
Third 1.37
Fourth 1.00
Fifth 0.86
Diff ratio: 3.90:1


VK M76 gear ratios:
First 3.23
Second 1.97
Third 1.26
Fourth 1
Fifth 0.79
Diff Ratio: 3.89:1

I know on the commodore forums there was a thread about swapping an MC6 to a M76 in a VK and the differences were..

-Speedo cable- completely different at gearbox end. (any ideas on how to get around this problem)
-Tailshaft- front half is shorter, rear half is identical.
-Clutch dust cover- just simply different.
-Lower gear boot.
-Upper gear boot- (can still use the MC6 one though)
-The top boot you see can be used with either gearbox.
-And obviously the gearstick is different
-Gearstick knob- sounds stupid to add but the thread sizes are completely different and i didnt have a suitable gear knob for it.

All the other stuff is the same eg.
-Clutch
-Gearbox mount/ cross member.
-The plate riveted onto the transmission tunnel.
-Clutch cable
-Lower bell housing cover.
-center console etc etc

So looking at that, the only real dramas should be the speedo cable and tailshaft..

Edited by sstorana, 25 January 2010 - 11:22 AM.


#4 Statler

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Posted 25 January 2010 - 11:18 AM

I fitted one to my UC hatch years back.
I simply folded over about 10mm of steel in the shifter [floor] hole to get clearance.

The only other issue i had was clearance for the extractors around the bellhousing.

It sounds like a sensible swap for you application.

One thing to note: Try to not use 5th gear under 80k's.

#5 _sstorana_

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Posted 25 January 2010 - 11:28 AM

I fitted one to my UC hatch years back.
I simply folded over about 10mm of steel in the shifter [floor] hole to get clearance.

The only other issue i had was clearance for the extractors around the bellhousing.

It sounds like a sensible swap for you application.

One thing to note: Try to not use 5th gear under 80k's.


Thanks for that..

Were you swapping from an MC6 or an M20?

As for 5th gear, it's only really needed on the freeway.

I would be interested in working out what sort of rpm's it will be running at, in 5th gear, with the two different ratios..

cheers
Mick

#6 Statler

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Posted 25 January 2010 - 11:31 AM

I went from the MC6....to a M21.....to the 5 slot. :)

I cant recall the differences in RPM, but it was very noticable.

Edited by coolngroovy, 25 January 2010 - 11:32 AM.


#7 76lxhatch

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Posted 25 January 2010 - 11:58 AM

-Speedo cable- completely different at gearbox end. (any ideas on how to get around this problem)

I've just removed a Starfire and 5 speed from a VK, pretty sure the cable is the same as the Trimatic and Aussie 4 speed so should be easy to find a Torana one. Must be just the MC6 one is different?

#8 _sstorana_

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Posted 25 January 2010 - 01:03 PM


-Speedo cable- completely different at gearbox end. (any ideas on how to get around this problem)

I've just removed a Starfire and 5 speed from a VK, pretty sure the cable is the same as the Trimatic and Aussie 4 speed so should be easy to find a Torana one. Must be just the MC6 one is different?


Damn!! Pity your not in NSW, Aust!!

Any chance of you taking some picture of the box, etc and sending them to me so I know what I am looking for?

cheers
Mick

#9 Heath

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Posted 25 January 2010 - 01:41 PM

MC6 is definitely different speedo cable

#10 Statler

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Posted 25 January 2010 - 02:28 PM

Mine came from a VH SL/X.
I dont recall having to do anything about the speedo cable. The Mbox cable fitted.

#11 76lxhatch

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Posted 25 January 2010 - 03:53 PM

Any chance of you taking some picture of the box, etc and sending them to me so I know what I am looking for?

No problem, what exactly do you want to see?

As above a bog stock speedo cable should work fine for you - the one you have now is the oddball, the one you would need is more common

#12 FastEHHolden

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Posted 25 January 2010 - 09:44 PM

I thought the box that came out in the VH was different to the VK one??....The VH box only came out behind 4's and the 173 blue......I had a VH box in the EH, speedo cable was the same (I think..unless i made one?? easy to do) but the tailshaft had to have a 2 inch chop.

#13 76lxhatch

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Posted 26 January 2010 - 06:21 AM

I think they're the same, although can't say that I've seen many VH ones, most of the 5 speeds around here are VKs. Yes the drive shaft needs to be shorter and uses a different spline yoke but I think its still a standard size uni so you could just grab the yoke and stick on the front of a shortened Torana shaft. Looking at what I have here the rear mount sits the same distance back but needs to be lifted higher too.

Will go take some pics soon

#14 76lxhatch

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Posted 26 January 2010 - 06:45 AM

OK a couple of pics:
Posted Image
Posted Image
The box and bell housing together are around 75mm longer than the Trimatic sitting next to it, pulled off an injected 3.3L six.
I've just noticed that I didn't cover the shifter hole and the box is now full of water, better do something about that...

Cross members, Trimatic vs 5 speed to suit VK Commodore (5 speed is the one with the mount still on it):
Posted Image

Drive shaft yoke, note the wider spline on the right side of the pic:
Posted Image

#15 Potta

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Posted 27 January 2010 - 05:16 PM


Assuming 4000 RPM at the moment in 4th at 1:1 ratio, here are the updated revs for the same speed in 5th Gear;
VK M76 - 3160

VH M76 - 3440




#16 _sstorana_

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Posted 27 January 2010 - 07:13 PM

thanks for that

#17 _sstorana_

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Posted 13 March 2012 - 08:31 PM

Hi Guys,

I finally got an M76 gearbox so I will be starting this conversion real soon. I will try and get some pics and info up as we go along for those that are thinking of doing the same sort of conversion.

cheers
Mick

#18 _ljharbsy_

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Posted 13 March 2012 - 09:01 PM

I am in the middle of rebuilding one of those boxes at the moment if you need a spare?

#19 Antman

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Posted 04 November 2019 - 01:55 PM

Chasing a main shaft speedo drive gear, any recommendations on where I can source one?



#20 Shiney005

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Posted 05 November 2019 - 10:43 AM

This website is a pain to navigate through, but have a look as they have some NOS sunbird stuff. It might be easier just to ring them.

 

Attached File  aa.JPG   76.31K   5 downloads


Edited by Shiney005, 05 November 2019 - 10:43 AM.


#21 Antman

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Posted 06 November 2019 - 11:37 PM

Thanks had a chat to the fellow there. Nice bloke. He sells stuff online that he has picked up from sales etc. A good site for random stuff. Definitely does not have a stock pile of anything in particular.

 

Seems like they were used in falcons (smaller engine models) in the same era and toyotas (corana?)

 

If anyone has a parts list for the M76 that  identifies part numbers that may help? Especially for others looking for parts for these. The main drive shaft is smaller than the T5

 

I am just wanting to get my speedo working so I can pass the pits. Would be great to get her on the road. Long term the box would not suit a bigger engine. However was hoping to drive her for a year or two first.

 

If any one has one of these in WA i would be interested

 

Or if anyone knows someone who may have something lying around. 

 

I was trying to post a pic. Is photo bucket still the way to go? seems like you have to pay for that now?

 

Cheers

Antman



#22 Shiney005

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Posted 07 November 2019 - 12:58 PM

There is a thread in here on how to post pics.  I just click on the "More Reply Options" button and then "Choose File". You have to watch your file sizes though. If it is a picture taken on a phone it might need to be re-sized smaller.

I think Max Ellery does a manual on Holden gearboxes, but probably no part numbers.



#23 Statler

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Posted 07 November 2019 - 04:31 PM

It's been a long time since I played with these but as i said, my speedo drive was the same as the M-box.

I'm going to assume (dangerous) that it operates off the same nylon drive cog on the output shaft? Shine a torch in the hole & see if you can see the cog.

#24 Antman

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Posted 07 November 2019 - 11:45 PM

I have the plastic main speedo drive out. I have sourced another one and its on its way. Hopefully it will suit. It has one less tooth on the outer, but we should be able to offset any change with a different cable drive gear.

Cheers 

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#25 yel327

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Posted 08 November 2019 - 06:44 AM

How many teeth on the drive gear? I’ll see what I can find for you in parts books.




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