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M21 Rebuild


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#1 _Kevhaze_

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Posted 28 January 2016 - 06:14 PM

Hello everyone,

I am in the process of rebuilding my M21 I got which I was told there was nothing wrong with it but was actually noisey in first and second😡. Now that I have got it apart it appears that my cluster gear and first gear both have some nice pitting so need replacing.

Who does everyone recommend getting the parts off?

Not sure yet why second gear was noisey at the moment as the needle rollers all looked fine.
It appears that the owner of the gearbox before me put a kit through it then found it was still noisey so sold it to me.... Bugger

Cheers Kev

#2 Lc69

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Posted 28 January 2016 - 09:15 PM

J & VR Transmisions
John Hall
02 98315772

Got some good parts for an M20 build last year.
Very helpful

#3 BIG KEV

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Posted 28 January 2016 - 09:34 PM

I have used John from VR also in the past.....Very helpful

#4 yel327

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Posted 29 January 2016 - 06:43 AM

I assume you means an Aussie 4spd, not a Saginaw or Muncie?

 

Kingswood Country sell new repro Aussie 4spd stuff.

 

Check the synchro teeth on 2nd gear to make sure it is still OK, and when you pull it apart check the mainshaft where 1st gear runs that it isn't buggered too. Whenever I've rebuilt Aussie 4spds in the past it is almost always a new cluster and 1st gear, and every second or third box will need a 2nd gear and/or a mainshaft. The input shafts are sometimes buggered too, check the case hardening on the inside where the needle rollers run, and the same on the mainshaft for the other side of the bearing.



#5 _Kevhaze_

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Posted 29 January 2016 - 07:39 PM

Yes sorry I mean Aussie,
I found Kingswood Country and ordered a first gear and new counter shaft so I should hopefully have it Monday or Tuesday, I am not sure on how the main shaft is but everything else looks good.

I do have pictures but I am unable to upload them at the moment.

The bit I am stumped on is where's the noise coming from on second gear?
When it's in 3rd or 4th it's great no noises at all.

Thanks guys for the details about J &VR transmissions, I will give him a call on Monday if I don't figure something out first

Cheers Kev

#6 _Kevhaze_

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Posted 29 January 2016 - 07:43 PM

Attached File  image.jpeg   226.64K   4 downloadsAttached File  image.jpeg   198.75K   5 downloads

As you guys can tell it has some nasty pitting on first but all the other gears look great

Cheers Kev

#7 yel327

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Posted 29 January 2016 - 08:10 PM

That is the case hardening wearing off. In 1st and 2nd more load is on that end of the cluster, and normally the bearing outer surface ( the cluster itself) is screwed at that end. 3rd puts more load on the other end of the cluster and 4th the cluster just spins as in 4th the input shaft is coupled to the main shaft.
So my guess is you'll find the cluster back end case hardening is screwed as well as the teeth.
When you pull it apart you can check if the case hardening on the nose of the main shaft is OK also inside the input shaft. Once you pull 1st gear off the main shaft look for damage to the nose of 1st and to the slots that 1st spins on. The circlip that secures 1st can disintegrate and cause this damage. The best thing is to use a good quality circlip when rebuilding.

#8 _Kevhaze_

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Posted 29 January 2016 - 08:29 PM

That is the case hardening wearing off. In 1st and 2nd more load is on that end of the cluster, and normally the bearing outer surface ( the cluster itself) is screwed at that end. 3rd puts more load on the other end of the cluster and 4th the cluster just spins as in 4th the input shaft is coupled to the main shaft.
So my guess is you'll find the cluster back end case hardening is screwed as well as the teeth.
When you pull it apart you can check if the case hardening on the nose of the main shaft is OK also inside the input shaft. Once you pull 1st gear off the main shaft look for damage to the nose of 1st and to the slots that 1st spins on. The circlip that secures 1st can disintegrate and cause this damage. The best thing is to use a good quality circlip when rebuilding.


Thanks mate, I thought it might just be first gear that's worn but the load on second might cause it to be noisey but I wasn't sure and thought I might ask some one with more experience with these gearboxes,

I just gotta steal a good pair of circlip plyers off my dad and I should be able to get first gear off for a better inspection

Cheers Kev

#9 yel327

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Posted 30 January 2016 - 07:20 AM

Either 1st or second will be loading up that end of the cluster and it is that end that the inner surface case hardening is always shagged, so my guess is that is why its noisy in 1st and 2nd. Doesn't matter though as the cluster is buggered. Make sure you buy all new needle rollers and other bearings.



#10 _Kevhaze_

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Posted 30 January 2016 - 01:14 PM

Thanks yel327 i bought a full rebuild kit before i pulled it out hoping that was all it needed and i got a suprise

Cheers Kev

#11 _Kevhaze_

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Posted 30 January 2016 - 07:03 PM

Well I managed to get all the gears off the main shaft and luckily enough it all looks good so once my parts show up I will chuck it all back together and finally after a 13 year rebuild I will finally get to take it for a nice cruise

Cheers Kev

#12 _Kevhaze_

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Posted 05 February 2016 - 01:10 PM

Good news everyone, I got the parts yesterday and put it all back together and this morning I put it back in the car.
Took it for a little spin and no noises drove great actually. Now I just have to give it a good run out the road.

Thanks for all your help it was greatly appreciated

Cheers Kev

#13 _Doggies73_

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Posted 31 March 2017 - 11:15 PM

I want to rebuild my M21, what's the publication to buy?

#14 grumpy xu1

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Posted 01 April 2017 - 04:16 PM

I think that if you look in member's projects and plans, go to marty's build, 3rd last page there's a Aussie 4 speed strip,& detailed rebuild in there mate. Gary.




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