Gearbox woes

Discuss mechanical problems here.

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ndevans
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Re: Gearbox woes

Postby ndevans » Mon Mar 25, 2019 12:06 am

Ok, I finally got the spare bellhousing cleaned up today. Came up quite well after 30min and some gunk.
What's the best way to clean up machined aluminium surfaces? Wire wool? Fine Emery/wet & dry?

Cheers N
cheers N
'69 Traveller, 1275, discs.

philthehill
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Re: Gearbox woes

Postby philthehill » Mon Mar 25, 2019 7:34 am

Scotch-brite pad with white spirit.


ndevans
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Re: Gearbox woes

Postby ndevans » Mon Mar 25, 2019 10:24 pm

philthehill wrote:
Mon Mar 25, 2019 7:34 am
Scotch-brite pad with white spirit.
Thanks. I've got it pretty clean, but it just needs a little more polishing.

Does anyone have a guide to gearbox serial numbers please?

Cheers N
cheers N
'69 Traveller, 1275, discs.

ndevans
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Re: Gearbox woes

Postby ndevans » Wed Mar 27, 2019 11:39 pm

Started stripping the box tonight. How do I get the plungers underneath the side cover out? They don't want to slide out. They're not stuck, there's plenty oil, but I can't get them out. Tried shaking the box, and tapping lightly with a hammer, but no joy.
cheers N
'69 Traveller, 1275, discs.

oliver90owner
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Re: Gearbox woes

Postby oliver90owner » Thu Mar 28, 2019 5:42 am

Magnet?

ndevans
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Re: Gearbox woes

Postby ndevans » Thu Mar 28, 2019 6:56 am

oliver90owner wrote:
Thu Mar 28, 2019 5:42 am
Magnet?
Thought that. Haven't got one small enough.
cheers N
'69 Traveller, 1275, discs.

les
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Re: Gearbox woes

Postby les » Thu Mar 28, 2019 10:00 am

Magnetise a nail head, or thin piece of bar, from your larger magnet.


ndevans
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Re: Gearbox woes

Postby ndevans » Thu Mar 28, 2019 10:57 pm

Tried a magnet, not happening!
I gave up in the end, took the front cover off, removed the selector rods, and it fell out!
Dismantling going well now, the layshaft fell out, one of the forks won't budge but I think that's because the 3rd motion shaft traps it. 3rd motion shaft removal tomorrow.
cheers N
'69 Traveller, 1275, discs.

ndevans
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Re: Gearbox woes

Postby ndevans » Sat Mar 30, 2019 9:36 pm

Ok, the current state of play is:
IMG_20190330_184917~2.jpg
IMG_20190330_184917~2.jpg (1.62 MiB) Viewed 854 times
IMG_20190330_193656~2.jpg
IMG_20190330_193656~2.jpg (1.35 MiB) Viewed 854 times
The gearbox is now stripped, apart from the 1st motion shaft. I've got the bearing loose in the aperture in the bellhousing, but can't get the 1st motion assembly out, because the sync cone (top picture) won't fit through the aperture.
The manual, both Haynes and BMC, says you just extract it, but it doesn't say how. Does the sync cone need to be drifted off the shaft? I've tried tapping inside the sync cone with a round bar, but it doesn't want to shift.
The bearing is tight on the shaft as well, and I can't get the locknut off, because I can't get a spanner in there, and it's very difficult to hold the shaft still anyway.
Any ideas please?

Cheers N
cheers N
'69 Traveller, 1275, discs.

pgp001
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Re: Gearbox woes

Postby pgp001 » Sat Mar 30, 2019 10:09 pm

There is a spring circlip on the outer race of the bearing that needs removing so the shaft can be withdrawn.
Have you seen this ?

http://www.dorsetmmoc.co.uk/wordpress/t ... ebuild.pdf

Phil

ndevans
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Re: Gearbox woes

Postby ndevans » Sat Mar 30, 2019 10:42 pm

pgp001 wrote:
Sat Mar 30, 2019 10:09 pm
There is a spring circlip on the outer race of the bearing that needs removing so the shaft can be withdrawn.
Have you seen this ?

http://www.dorsetmmoc.co.uk/wordpress/t ... ebuild.pdf

Phil
I have seen that, thank you, and very good it is too, but it doesn't deal with the strip down.
I have seen the circlip, but haven't removed it yet, because the Haynes manual says to tap it into the bellhousing. I'll give that a go tomorrow. Thanks.

Cheers N
Last edited by ndevans on Sat Mar 30, 2019 11:18 pm, edited 1 time in total.
cheers N
'69 Traveller, 1275, discs.

Mark Wilson
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Re: Gearbox woes

Postby Mark Wilson » Sat Mar 30, 2019 10:48 pm

Sorry to be vague, because it's a couple of years ago since I did this, but I do remember trying to use brute force to get the first motion shaft out through that aperture, and then working out it had to be removed the opposite direction to the way Haynes shows it.

pgp001
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Re: Gearbox woes

Postby pgp001 » Sat Mar 30, 2019 11:29 pm

I am pretty sure if the circlip is removed, the whole first motion shaft assembly will push into the gearbox.
Note......I have not done this myself, just what I assume from reading that article and seeing the photo's

I have stripped and rebuilt plenty of Austin 7 and motorcycle gearboxes, sometimes you have to warm the alloy case to remove a bearing without using brute force, but I dont think that is the case on a Minor gearbox.

Phil

ndevans
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Re: Gearbox woes

Postby ndevans » Sun Mar 31, 2019 7:02 pm

Managed to get it out by removing the circlip, then gently tapping the bearing back through the aperture. I then spent 1/2hr tapping away with a drift on the lock nut, which eventually came loose.
Next question-how do I remove the bearing from the 1st motion shaft?

Cheers N
cheers N
'69 Traveller, 1275, discs.

ndevans
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Re: Gearbox woes

Postby ndevans » Tue Apr 02, 2019 11:05 pm

Success, I managed to get the first motion bearing off the shaft. I heated it in the oven at 100deg C for 15min, then held it in a vice, wrapped in a welding glove. I then used a thin drift to tap all around the bearing. It slowly moved over the threads, then dropped off.

So the gearbox is now completely stripped down to it's component pieces. I am going to replace both bearings, as the rear one is shot, and I don't see the point in just replacing 1. I will also try to get a replacement 1st gear, as mine is a bit battered.

Is there anything else I should replace whilst I have it all apart? I'll be replacing all the seals and gaskets, obviously.

Cheers N
cheers N
'69 Traveller, 1275, discs.

ndevans
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Re: Gearbox woes

Postby ndevans » Tue Apr 16, 2019 12:27 am

I'm starting to rebuild the box now. I have all I need except the rear laygear thrust washer, which is on order.
The layshaft and layshaft bearings are being replaced, but I don't have either the circlip or the distance piece. I don't recall either coming out when I dismantled it. Do new laygear bearings not require the distance piece and circlip? The rear bearing seems to sit about 1/2" inside the laygear, when assembled on the shaft.
cheers N
'69 Traveller, 1275, discs.

philthehill
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Re: Gearbox woes

Postby philthehill » Tue Apr 16, 2019 8:09 am

The spacer Pt No: 22G277 is there to ensure that the needle roller bearing is kept at the right distance from the inner circlip and on the internal needle roller path of the layshaft.

Therefore the spacer must be fitted.

The outer end of the needle roller bearing should be either just inside the outer circlip groove or just below the outer thrust face of the layshaft.

The current batch of layshaft needle roller bearings tend to be longer than the originals so as not to allow the outer circlip to be fitted. Not fitting the outer circlip is acceptable as the needle roller cage cannot move outwards as it is restrained by the thrust washer.


ndevans
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Re: Gearbox woes

Postby ndevans » Tue Apr 16, 2019 2:13 pm

Ok thanks. Either it wasn't there, or it fell out as I removed the laygear. I'll have a look on the garage floor tonight.
cheers N
'69 Traveller, 1275, discs.

ndevans
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Re: Gearbox woes

Postby ndevans » Tue Apr 16, 2019 10:31 pm

No sign of a distance piece anywhere.
Here is a photo of the rear end of the laygear.
IMG_20190416_221807~2.jpg
IMG_20190416_221807~2.jpg (1.08 MiB) Viewed 548 times
The bearing is visible inside the laygear. The top of the bearing is about 5mm below the circlip groove, and 8mm below the end of the laygear. Is this where the bearing should sit with the distance piece in place? There's nothing else loose inside the shaft. Would the distance piece be loose, or moveable?
The new bearing is the same size as the old one.

Cheers N
cheers N
'69 Traveller, 1275, discs.

philthehill
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Re: Gearbox woes

Postby philthehill » Wed Apr 17, 2019 7:51 am

It could be that the spacer was left out on a previous gearbox rebuild.
The spacer is a loose/push fit inside the layshaft
The needle roller bearing should be either just below the circlip/circlip groove or just below the thrust face/end of the layshaft.
I personally would not rebuild the gearbox minus the spacer. It is there for a purpose and should be in place.
It could be that the roller bearing (pictured) has hit the bottom of the machined roller path. The spacer keeps the roller bearing on the roller path. If the roller bearing is not kept on the roller path it could cause unnecessary wear to the bearing, lay shaft and lay gear.

See BMC wksp manual drawing Fig FF9 for the correct component assembly drawing.



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