Gearbox 1st and 2nd gear bush replacement

mschmitz57 · Jul 11, 2014

Since I've got my gearbox open for a layshaft bearing replacement, I thought I'd freshen things up a bit while I'm waiting for layshaft shims.
I noticed a bit of play on the 1st and 2nd gear bushes, so I ordered a couple new ones from Old Britts.
I test fitted the new 1st gear bush (no gear) on the layshaft and noticed it wasn't exactly snug either, so maybe the old bush is fine.
Now of course this is probably because it hasn't been squeezed by the interference fit of the gear.
I'm now considering leaving the original bush's in place because the trans actually shifted quite nicely.
Does anyone replace these routinely? Do the new 1st and 2nd gear bushes (Andover Norton parts) require reaming or should they be a perfect fit?
I'd like to know before I drive a perfectly good bush out of the gears.
I've watched John Hudson drive these bushes out with a few sockets and a hammer and he never mentions reaming them.

Gearbox 1st and 2nd gear bush replacement

L.A.B. · Jul 11, 2014

Only the 1st gear bush should be an interference fit in the gear, and that bush ought to be replaced as a matter of routine because it is relatively thin and can break up.

mschmitz57 said:
I've watched John Hudson drive these bushes out with a few sockets and a hammer and he never mentions reaming them.

The 2nd gear bush should be a sliding fit, and genuine AN gearbox bushes shouldn't need reaming according to Mick Hemmings in his NOC gearbox rebuild video.

pete.v · Jul 11, 2014

I guess it is safe to assume that your primary is in place and the all important sleeve gear is unavailable to receive new bushes? That's a shame.

Hobot · Jul 11, 2014

Check to see if ya can detectably tip 2nd on its shaft with bush, if can then worry about the dog faces smearing out till won't shift, if no significant tip slack on bush wear then just use it up till next 1st bush wears out. While in there oil groove the sleeve bushes as can't get oil in and slings oil out except when in 4th for some drool in oiling. Also add worn bush spacer in middle or fit 2 longer bushes. Sleeve bushes are below resting oil level.

mschmitz57 · Jul 11, 2014

Yup, I'm leaving the primary on this time `round. Gearbox was shifting flawlessly until layshaft bearing took a dump.
I have records from P.O. stating that main shaft bearing were replaced not long ago. I'll have to see if sleeve gear bush was replaced.
I'm a lazy slacker, I know.

pete.v · Jul 11, 2014

mschmitz57 said:
Yup, I'm leaving the primary on this time `round. Gearbox was shifting flawlessly until layshaft bearing took a dump.
I have records from P.O. stating that main shaft bearing were replaced not long ago. I'll have to see if sleeve gear bush was replaced.
I'm a lazy slacker, I know.

Sounds like you have it covered.

mschmitz57 · Jul 13, 2014

I devised a puller using a bolt, sockets, and some thick washers and nut which worked great.
The bush was TIGHT. I used the puller to pull the new AN bush into the gear but now the bush is too tight on the layshaft.
I measure around 17.35mm ID on one side and 17.25mm ID on the inner edge (with the taper). The tapered edge may have deformed
slightly as it was driven in. Who knows.

The gear actually fits snug on the layshaft until the outer edge of the bush reaches the shaft, then it goes tight.

What's a good way to ream this slightly without buying yet another tool?
Will a suitable sized rod with some ultra fine emery paper suffice?

cjandme · Jul 13, 2014

mschmitz57 said:
Will a suitable sized rod with some ultra fine emery paper suffice?

Wellllll, how much time to you have to spend on it ?

auldblue · Jul 13, 2014

cjandme said:
mschmitz57 said:

Will a suitable sized rod with some ultra fine emery paper suffice?

Click to expand...

Wellllll, how much time to you have to spend on it ?

You are good at inventing tools mark , see what you can do . What would John Hudson have done?

mschmitz57 · Jul 13, 2014

John Hudson would have used some rusty old British dental tools from the 60's.

auldblue · Jul 13, 2014

mschmitz57 said:
John would have used some old British dental tools from the 60's.

Looks like you've had it then Austin powers. Why do I think you're not kidding?

Hobot · Jul 13, 2014

Mr Hudson trained me so know he'd just sand longer till slip on fit and then start an oil rag fire on the bench after expanding something that hadn't been able to sand to fit prior.

mschmitz57 · Jul 13, 2014

OK Auld. I accept your challenge.

An 11mm deep socket wrapped with some #600 emery was a perfect fit and worked a treat.
Some WD40 as a cutting lube and a few minutes of spinning the gear had the bush surface nicely polished.
Norton would undoubtedly still be in business had they hand-fitted all parts like I do.
Moving on to 2nd gear bush. Where's that Guinness?

auldblue · Jul 13, 2014

Mark

Thanks for the tip , you can proudly wear the red N. Unfortunately I am still an apprentice. Good on you hope your box shifts nice and smooth.

J

L.A.B. · Jul 13, 2014

mschmitz57 said:
Moving on to 2nd gear bush.

Mick Hemmings says in his video that : ...mainshaft second gear bush should be free floating, and if it's not, then get some Emery cloth in, and clean this [inside 2nd gear] out...."

mschmitz57 · Jul 13, 2014

The old 2nd gear bush required just a nudge and then it slid right out as advertised. New bush slid right into gear.
New bush was slightly tight on main shaft and required a little bit of sanding to remove burrs around the oil holes.

Now waiting for lay shaft shims and a new kickstart pawl.

mschmitz57 · Jul 20, 2014

A follow-up.

I had to shim the layshaft .030" to achieve a .005" cold end-float. I used a .010 and .020 Isolastic shims from Old Britts.
They required a little work with my Dremel to fit properly.

Also replaced the kick-start pawl and shift pawl spring. The spring required a little bending adjustment to get a slight clearance between
shift pawl and spring. Also replaced all rubber seals in outer GB cover.

Button-ed everything up, refilled GB and primary. Took a test ride last night.
Shifts like butter.

Gearbox 1st and 2nd gear bush replacement

mschmitz57

L.A.B.

Moderator

pete.v

Hobot

mschmitz57

pete.v

mschmitz57

cjandme

auldblue

mschmitz57

auldblue

Hobot

mschmitz57

auldblue

L.A.B.

Moderator

mschmitz57

mschmitz57

Similar threads