Layshaft bearing failure (2014)

f you suspect you might have a Portugal bearing in your GB and you've never opened-up a transmission I suggest you do it.

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but the portugese are renouned for their bearings . :? :shock: :x :roll:

Good to see we're not all Heath Robinson . 8)

Probably nothing inherently wrong with the Portugal bearing other than the application in a British gearbox with a flexy layshaft
and a fragile ball cage. Then again the Portuguese ARE shifty little bastards.

(that was a joke)

Congrats. Now drop that new bearing into the freezer next to the kid's popsicles. You're going to be heating up the box again too.

Still waiting for new bearings and bushes. Also going to replace the outer main shaft bearing as long as I have it apart as it's an easy swap.
Also I noticed that the 1st and 2nd gear bush are a bit sloppy so I should replace them as well.

Check the sleeve gear bush(s) for galling from lack of oil. Check for wear by grabbing mainshaft and look for sideways movement.

mschmitz57 said:

It's very straightforward. The AMC box is dead simple. It's not hard work. And if your bearing is still intact it makes it so much easier to remove.
I was very fortunate to have this fail in front of my house at 20mph. It gave me no warning before this happened.

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So happy to see everything worked out well. Have you been able to identify any cracking between the bearing bores? Based on your experience, I may just have to break down and pull mine apart before my big August ride. And yes, I did lose sleep worrying about it (and you).

Nathan

Crap. I knew you were going to ask me that question (thank you very much).

Yes, there is a tiny microscopically small hairline crack in the narrow web between the bores. I cannot feel it with my fingernail in the bearing bore. I'm going to ignore it since it clearly doesn't affect the fit of the bearing and the thin alloy web can't possibly add any strength in that area.
I've read all the opinions on this and decided it's quite common and it's probably been cracked for decades. I'll blame questionable GB design and variations in the casting processes as to why some boxes have not yet cracked. I bet some bearing pockets may be slightly undersized causing the bearing insertion to force the material to stretch and crack. Certainly that thin web must be under tension just waiting for a release in the form of an extreme downshift or too tight primary or drive chain. Can anyone show me a picture where these cracks have propagated to the outside of the shell, or caused some other type of failure (have I rationalized this enough?)

Have we seen the newly manufactured GB shells from Andover Norton crack in a similar fashion?

As they say, I've got bigger fish to fry.

Don't sweat the tiny crack between the 2 bearing bores.

Nater_Potater said:

mschmitz57 said:

I'll heat the GB shell with the puller attached to the
outer race which should act like a heat sink for the steel race keeping it slightly cooler. That's my theory anyway.

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Try some of this http://www.alliedelec.com/search/produc ... fgodWiQAKA just as you get ready to bump the slide hammer. With the aluminum case warm, the sudden chill to the race should assist in gaining some extra clearance.

Thanks a lot for starting this stupid thread! I'm now officially going to lose sleep, wondering when my 74's going to grenade on me!

Nathan

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Its better not to think of it as a problem but an opportunity for a solution. And at least then you will know
The hairline crack is not a problem but the standard bearing is

Jed

Jed

Are you going to start chanting and burning incense!

DogT said:

That puller may work if it will get behind the race. I got the head of my screws behind it so there must be a bit of distance there. I found it. It's a bit of rube goldberg of course and it was a real pain to get the screw heads lined up.

I had 2 GB that I had to use it on. I just couldn't' get the heat to work unless I was afraid of too much heat. I used a gas grill and the crank case shells fell right out but not the GB.

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Good tips in this thread for layshaft removal methods.
Anyone ever consider using the grease/paper towel hydraulic pressure trick as done by this guy (around 4:30 mark):

good luck if it is an open bearing as the grease will go through before it ever builds pressure.

Tornado said:

Good tips in this thread for layshaft removal methods.
Anyone ever consider using the grease/paper towel hydraulic pressure trick as done by this guy (around 4:30 mark):

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bill said:

good luck if it is an open bearing as the grease will go through before it ever builds pressure.

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The one in the video and others I've seen are "open"....I think that's the purpose of using the shop towel or other material to really get it to pack in, not ooze out. First time I saw this technique was with wet newpaper bits being packed into a blind bearing...quite a lot larger than our layshaft....was messy but it sure did work nicely.