Discussion:
BMC C series gearbox code
(too old to reply)
webmonster
2009-05-16 07:08:50 UTC
Permalink
I've got a 1958 Morris Isis and I've just bought an overdrive gearbox
that was fitted to a Wolseley 6/90.
This should be a 4-speed gearbox but unfortunately I suspect that it
is a 3 speed overdrive unit from a 6/99 because on the top of the
gearbox is a 'badge' which says Type 29-O-3
Can anyone here confirm/deny that I've got the wrong gearbox?

thanks in advance,
--
Robert
Dave Plowman (News)
2009-05-16 08:39:21 UTC
Permalink
In article
Post by webmonster
I've got a 1958 Morris Isis and I've just bought an overdrive gearbox
that was fitted to a Wolseley 6/90.
This should be a 4-speed gearbox but unfortunately I suspect that it
is a 3 speed overdrive unit from a 6/99 because on the top of the
gearbox is a 'badge' which says Type 29-O-3
Can anyone here confirm/deny that I've got the wrong gearbox?
I've a feeling those three speed boxes are in fact four speed ones with
first inhibited by the selector mechanism - so could well be just fine if
you use the right bits from your original. IIRC, there was a floor
gearchange conversion for that series which 'released' first gear.

There can't be many Isis left on the roads - pretty rare car even when new.
--
*Why isn't there mouse-flavoured cat food?

Dave Plowman ***@davenoise.co.uk London SW
To e-mail, change noise into sound.
webmonster
2009-05-16 22:49:29 UTC
Permalink
Hi Dave,
Post by Dave Plowman (News)
I've a feeling those three speed boxes are in fact four speed ones with
first inhibited by the selector mechanism - so could well be just fine if
you use the right bits from your original. IIRC, there was a floor
gearchange conversion for that series which 'released' first gear.
I've got a 6/99 and Isis workshop manuals and although the gearboxes
are very similar, the layshaft gears and the mainshaft look very
slightly different.
The later 6/110 has a floor change 4-speed 'box, but this looks quite
different.

Given that the overdrives themselves are the same unit what I really
need is the right mainshaft. If I was brave I'm sure I could get my
existing mainshaft shortened and machined to suit.
Post by Dave Plowman (News)
There can't be many Isis left on the roads - pretty rare car even when new.
True - I've only seen a photo of one other (a nice red one) on the
road here in NZ. Both the red car and my Isis are the late ones with
the RH floor change and the little fins at the back.
I wonder why they never sold well when new. It certainly goes and
handles quite adequately (running on radials and I've renewed all the
steering/suspension bushes).

regards,
--
Robert
Dave Plowman (News)
2009-05-17 11:06:01 UTC
Permalink
In article
Post by Dave Plowman (News)
I've a feeling those three speed boxes are in fact four speed ones
with first inhibited by the selector mechanism - so could well be just
fine if you use the right bits from your original. IIRC, there was a
floor gearchange conversion for that series which 'released' first
gear.
I've got a 6/99 and Isis workshop manuals and although the gearboxes are
very similar, the layshaft gears and the mainshaft look very slightly
different.
It would be easy to tell from that if it were a true three speed box or a
modified four?
The later 6/110 has a floor change 4-speed 'box, but this
looks quite different.
I'm not well up on this series - but I'll ask my brother who has had
several 6 cylinder BMC cars. Indeed he may have a spare A95 box which is 4
speed column change. Although I know he had a clear out of such things
when scrap prices were high.

The 'B' series box had openings top and side to allow the same basic box
to work with either floor or column change - I assumed the 'C' series one
was the same.
Given that the overdrives themselves are the same unit what I really
need is the right mainshaft. If I was brave I'm sure I could get my
existing mainshaft shortened and machined to suit.
Post by Dave Plowman (News)
There can't be many Isis left on the roads - pretty rare car even when new.
True - I've only seen a photo of one other (a nice red one) on the
road here in NZ. Both the red car and my Isis are the late ones with
the RH floor change and the little fins at the back.
I wonder why they never sold well when new. It certainly goes and
handles quite adequately (running on radials and I've renewed all the
steering/suspension bushes).
The Austin version was far more common here. Dunno why. The Isis looked
perhaps rather ungainly against it, though. But beauty is in the eye of
the beholder. ;-)
--
*If you remember the '60s, you weren't really there

Dave Plowman ***@davenoise.co.uk London SW
To e-mail, change noise into sound.
Robert Greenfield
2009-05-18 09:11:29 UTC
Permalink
Post by Dave Plowman (News)
In article
Post by webmonster
I've got a 6/99 and Isis workshop manuals and although the gearboxes
are very similar, the layshaft gears and the mainshaft look very
slightly different.
It would be easy to tell from that if it were a true three speed box or a
modified four?
Not for a gearbox oaf like me.
"Look! whirring bits and pieces!"
;-)

I'll open up the 'box and have a look. That will settle it.
Post by Dave Plowman (News)
The 'B' series box had openings top and side to allow the same basic box
to work with either floor or column change - I assumed the 'C' series one
was the same.
From what I can tell, all early C-series gearboxes were linkage driven -
they all had a shifter and selector lever on the side. Even the Healeys
had their centre floor shift lever offset to the left.
Post by Dave Plowman (News)
Post by webmonster
True - I've only seen a photo of one other (a nice red one) on the
road here in NZ. Both the red car and my Isis are the late ones with
the RH floor change and the little fins at the back.
I wonder why they never sold well when new. It certainly goes and
handles quite adequately (running on radials and I've renewed all the
steering/suspension bushes).
The Austin version was far more common here. Dunno why. The Isis looked
perhaps rather ungainly against it, though.
The series I Isis looks a little out of proportion to my eye, but the
little fins and 2-tone paint work of the series II Isis look better to me.
Post by Dave Plowman (News)
But beauty is in the eye of the beholder. ;-)
True. And I like my Isis :-)

regards,
--
Using Windows is such a pleasure

Robert Greenfield
change rockcave to caverock to email if you so desire.
Roger
2009-05-18 11:36:51 UTC
Permalink
Post by Robert Greenfield
From what I can tell, all early C-series gearboxes were linkage driven -
they all had a shifter and selector lever on the side. Even the Healeys
had their centre floor shift lever offset to the left.
The 1955 BN1 I had back in 1969 had the gearstick offset to the left and
the gate transposed as well. (IIRC top was left and back). First was
supposed to be blanked off (leaving 3 gears) but wasn't and the O/D was
only supposed to work with the top 2 gears but would have worked with
all.
--
Roger Chapman
Dave Plowman (News)
2009-05-18 13:29:44 UTC
Permalink
Post by Dave Plowman (News)
In article
Post by webmonster
I've got a 6/99 and Isis workshop manuals and although the gearboxes
are very similar, the layshaft gears and the mainshaft look very
slightly different.
It would be easy to tell from that if it were a true three speed box
or a modified four?
Not for a gearbox oaf like me. "Look! whirring bits and pieces!" ;-)
I'll open up the 'box and have a look. That will settle it.
Assuming they are genuine BMC manuals they'll include line drawings of the
box? My Magnette ZA one does. So just count the gears on the layshaft. The
one at the front is the drive gear off the input shaft. The next one along
first gear, then second, etc. No gear for top as that is direct - the
input and output shafts get locked together.

First gear (on the four speed) is spur teeth - ie at right angles to the
shaft, and slides to engage the rest helical cut and are constant mesh,
the engagement being by synchromesh clutches.

I thought all these boxes were four speed - the old first gear still being
needed for reverse.
Post by Dave Plowman (News)
The 'B' series box had openings top and side to allow the same basic
box to work with either floor or column change - I assumed the 'C'
series one was the same.
From what I can tell, all early C-series gearboxes were linkage driven -
they all had a shifter and selector lever on the side. Even the Healeys
had their centre floor shift lever offset to the left.
Right.
Post by Dave Plowman (News)
Post by webmonster
True - I've only seen a photo of one other (a nice red one) on the
road here in NZ. Both the red car and my Isis are the late ones with
the RH floor change and the little fins at the back.
I wonder why they never sold well when new. It certainly goes and
handles quite adequately (running on radials and I've renewed all the
steering/suspension bushes).
The Austin version was far more common here. Dunno why. The Isis looked
perhaps rather ungainly against it, though.
The series I Isis looks a little out of proportion to my eye, but the
little fins and 2-tone paint work of the series II Isis look better to me.
Post by Dave Plowman (News)
But beauty is in the eye of the beholder. ;-)
True. And I like my Isis :-)
I learned to drive on my father's Series II Oxford - ie the same basic
body.
regards,
--
*Why don't sheep shrink when it rains?

Dave Plowman ***@davenoise.co.uk London SW
To e-mail, change noise into sound.
Robert Greenfield
2009-05-19 08:57:16 UTC
Permalink
Post by Dave Plowman (News)
Assuming they are genuine BMC manuals they'll include line drawings of
the box? My Magnette ZA one does. So just count the gears on the
layshaft. The one at the front is the drive gear off the input shaft.
The next one along first gear, then second, etc. No gear for top as that
is direct - the input and output shafts get locked together.
First gear (on the four speed) is spur teeth - ie at right angles to the
shaft, and slides to engage the rest helical cut and are constant mesh,
the engagement being by synchromesh clutches.
I thought all these boxes were four speed - the old first gear still
being needed for reverse.
The reverse idler on the Isis diagram has spur teeth whilst the 6/99's
idler has helical cut gears.

Actually... thanks to your good description above I think I can see what
is the main difference -
On the Isis the smallest gear on the layshaft has spur teeth.

On the 6/99 the layshaft has the same number of gears, but the smallest
gear has helical cut teeth and the gear next to it is *exactly* the same
size (so the equivalent to 1st and 2nd gear on the Isis are identical -
solves the reverse-speed dilemma).
Post by Dave Plowman (News)
I learned to drive on my father's Series II Oxford - ie the same basic
body.
I've got a series II Oxford too - my first car which I bought when I was
19. It was a real minter - 54,000miles when I bought it - 2 previous
owners. Now I'm the ripe old age of 34 (and the Oxford has done
89,000miles) and I've got it off the road for a 'quick tidy-up'.
The boot and engine bay need a repaint and the engine is getting a bit
tired. And the gearchange linkages need re-bushing and I want a new
gearlever knob (column change - the white plastic has cracked like they
all do).

regards,
--
"Geoffery, Bungle's going out" ... "Well put some more petrol on him then!"

Robert Greenfield
change rockcave to caverock to email if you so desire.
Dave Plowman (News)
2009-05-19 16:09:21 UTC
Permalink
Post by Robert Greenfield
Post by Dave Plowman (News)
I thought all these boxes were four speed - the old first gear still
being needed for reverse.
The reverse idler on the Isis diagram has spur teeth whilst the 6/99's
idler has helical cut gears.
Actually... thanks to your good description above I think I can see what
is the main difference -
On the Isis the smallest gear on the layshaft has spur teeth.
Yes - what I'd suspect.
Post by Robert Greenfield
On the 6/99 the layshaft has the same number of gears, but the smallest
gear has helical cut teeth and the gear next to it is *exactly* the same
size (so the equivalent to 1st and 2nd gear on the Isis are identical -
solves the reverse-speed dilemma).
Right. So it looks like a specially made three speed. Perhaps the later
engines produced too much torque for the basic box and this was the way
round?
Post by Robert Greenfield
Post by Dave Plowman (News)
I learned to drive on my father's Series II Oxford - ie the same basic
body.
I've got a series II Oxford too - my first car which I bought when I was
19. It was a real minter - 54,000miles when I bought it - 2 previous
owners. Now I'm the ripe old age of 34 (and the Oxford has done
89,000miles) and I've got it off the road for a 'quick tidy-up'.
The boot and engine bay need a repaint and the engine is getting a bit
tired. And the gearchange linkages need re-bushing and I want a new
gearlever knob (column change - the white plastic has cracked like they
all do).
There's a silly bent wire link which fits into rubber bushes and makes the
change very sloppy - even when perfect. My father, who was an engineer,
replaced it with a rose jointed arrangement. Said it improved things no
end - but I only ever drove it after the mod so can't comment on the
difference.
Post by Robert Greenfield
"Geoffery, Bungle's going out" ... "Well put some more petrol on him then!"
That was the very first programme I worked on after moving from the BBC to
Thames TV and was delighted to see how everyone sent it up after the
deadly serious BBC children's department.
--
*When it rains, why don't sheep shrink? *

Dave Plowman ***@davenoise.co.uk London SW
To e-mail, change noise into sound.
Robert Greenfield
2009-05-30 09:20:21 UTC
Permalink
Well, I got permission from the owner to open up the gearbox and yes, it
is a smelly 3-speed from a 6/99, not a 4-speed. Rats.
I also found out why it is jammed - the selector lever has had a hell of a
belt at some time (it has been welded to mend it); this has forced it to
jump out of its slot internally.
Seems a bit silly for BMC to have the external lever pointing downwards.
On my Isis both levers point upwards - out of the way of rocks etc.

In article <***@davenoise.co.uk>,
Dave Plowman (News) <***@davenoise.co.uk> wrote:

<re: Oxford II gearchange>
Post by Dave Plowman (News)
There's a silly bent wire link which fits into rubber bushes and makes
the change very sloppy - even when perfect. My father, who was an
engineer, replaced it with a rose jointed arrangement. Said it improved
things no end - but I only ever drove it after the mod so can't comment
on the difference.
My Oxford is a late series II with many (most? all??) of the factory mods
already installed for the gearchange. They must have made these changes
for a reason :-)

I've always thought it is quite a nice gearchange until recently when I
noticed I was stuggling more often to find 1st or 2nd.
The other oddity is that the reverse gear 'lockout' on the column lever
needs a surprising pull overcome the spring. My wife can't easily get the
Oxford into reverse.
Post by Dave Plowman (News)
Post by Robert Greenfield
"Geoffery, Bungle's going out" ... "Well put some more petrol on him then!"
That was the very first programme I worked on after moving from the BBC
to Thames TV and was delighted to see how everyone sent it up after the
deadly serious BBC children's department.
It was a fun show :-)

regards,
--
"That's not right. It shouldn't do that" - helpful comment by old car folk

Robert Greenfield
change rockcave to caverock to email if you so desire.
Jim Warren
2009-05-30 10:11:47 UTC
Permalink
Post by Robert Greenfield
I've always thought it is quite a nice gearchange until recently when I
noticed I was struggling more often to find 1st or 2nd.
The other oddity is that the reverse gear 'lockout' on the column lever
needs a surprising pull overcome the spring. My wife can't easily get the
Oxford into reverse.
Just a thought - have you tried disconnecting the change mechanism from
the gearbox and testing how the column change feels when unconnected?
It is possible that the problems you are experiencing could be in the
mechanism rather than the gearbox.

My brother had a column change Ford years ago, and when he thought he
had gearbox difficulties it turned out to be a column linkage bush instead.

Also, make sure the 3rd/4th selector returns cleanly to neutral before
the column can go across to the 1st/2nd position or the interlock in the
gearbox can block the engagement of the lower gears. The Ford had
adjustments on the linkage between the rods at the bottom of the column
and the gearbox, but I don't know the BMC layout so you may or may not
have similar adjustments available. But I thought I would mention it
because it might be something you hadn't thought of.

Jim
Robert Greenfield
2009-06-01 08:59:17 UTC
Permalink
Hi Jim,
Post by Jim Warren
Just a thought - have you tried disconnecting the change mechanism from
the gearbox and testing how the column change feels when unconnected?
It is possible that the problems you are experiencing could be in the
mechanism rather than the gearbox.
My brother had a column change Ford years ago, and when he thought he
had gearbox difficulties it turned out to be a column linkage bush instead.
I am 90% certain that the problems are in the mechanism/linkages rather
than the gearbox.
Post by Jim Warren
Also, make sure the 3rd/4th selector returns cleanly to neutral before
the column can go across to the 1st/2nd position or the interlock in the
gearbox can block the engagement of the lower gears.
Hmm! I hadn't thought of that. Thanks.
Post by Jim Warren
The Ford had
adjustments on the linkage between the rods at the bottom of the column
and the gearbox, but I don't know the BMC layout so you may or may not
have similar adjustments available.
I'll need to have a look - I'm sure the ball-jointed linkages will have
some adjustment, however I doubt this will make up for slogged out bushes.

regards,
--
D.ont R.elax U.ntil G.randma's S.ober

Robert Greenfield
change rockcave to caverock to email if you so desire.
Mike P
2009-05-17 11:44:52 UTC
Permalink
Post by Dave Plowman (News)
In article
Post by webmonster
I've got a 1958 Morris Isis and I've just bought an overdrive gearbox
<snip>
Post by Dave Plowman (News)
There can't be many Isis left on the roads - pretty rare car even when new.
36 left on the road in the UK according to this month's Practical
Classics. Of course, that doesn't say how many are lying in barns, fields
or garages.

Mike P
Robert Greenfield
2009-05-18 09:15:11 UTC
Permalink
Post by Mike P
Post by Dave Plowman (News)
There can't be many Isis left on the roads - pretty rare car even when new.
36 left on the road in the UK according to this month's Practical
Classics. Of course, that doesn't say how many are lying in barns,
fields or garages.
That figure will be both series I and II, I imagine. How does that compare
to the A90 and A95 I wonder?

I wonder how many might be left on the road here in NZ.

regards,
--
Pandas will eat only bamboo; I will eat only chocolate biscuits...

Robert Greenfield
change rockcave to caverock to email if you so desire.
p***@gmail.com
2013-03-30 19:48:11 UTC
Permalink
Post by webmonster
I've got a 1958 Morris Isis and I've just bought an overdrive gearbox
that was fitted to a Wolseley 6/90.
This should be a 4-speed gearbox but unfortunately I suspect that it
is a 3 speed overdrive unit from a 6/99 because on the top of the
gearbox is a 'badge' which says Type 29-O-3
Can anyone here confirm/deny that I've got the wrong gearbox?
thanks in advance,
--
Robert
Dave Plowman (News)
2013-03-30 23:46:02 UTC
Permalink
2009. május 16., szombat 9:08:50 UTC+2 idõpontban webmonster a
Post by webmonster
I've got a 1958 Morris Isis and I've just bought an overdrive gearbox
that was fitted to a Wolseley 6/90. This should be a 4-speed gearbox
but unfortunately I suspect that it is a 3 speed overdrive unit from
a 6/99 because on the top of the gearbox is a 'badge' which says Type
29-O-3 Can anyone here confirm/deny that I've got the wrong gearbox?
thanks in advance,
--
Robert
IIRC, it is still the same four speed internally. If you have both, it
should be possible to make a good one from the two.
--
*TEAMWORK...means never having to take all the blame yourself *

Dave Plowman ***@davenoise.co.uk London SW
To e-mail, change noise into sound.
z***@gmail.com
2015-11-14 09:16:47 UTC
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