Manual Gearbox - 3 Synchro Internal Components

Manual Gearbox - 3 Synchro Internal Components
No. Part No. Description Qty. Remarks No. Part No. Description Qty. Remarks
The 3 Synchro Gearbox
1959-68
Fitted to all Minis between 1959 and 1968, the 3 synchro gearbox is so called because synchromesh is
only available on 2nd, 3rd and 4th gears, 1st gear being of the ‘crash’ engagement type. Probably the
most common fault on this gearbox is jumping out of first gear, followed closely by laygear bearing and
layshaft failure. A proper first speed gear was inserted in the gearbox in 1968, at last receiving the
great benefit of synchromesh engagement; this gearbox is known as the 4 synchro and its internal
components are covered in the next section of the catalogue.
If you’ve not been inside a 3 synchro Mini gearbox before or you can’t remember when you last did,
please read these notes carefully - they could save you a lot of heartache. The gearbo x internal
components were revised several times , with the changes being introduced at broadly the same times
across all of the A series engined cars in the BMC range . Essentially, these revisions boil down to three
types of gearbox (with a handful of components being awkward exceptions to the rule, of course... w e’ll
explain those as best we can as we go along).
The first 3 synchro gearbox fitted to the Mini is known as the ‘cone synchromesh’ gearbox, because of
its use of cones to aid gearchanging rather than the more efficient baulk rings, which arrived in 1962.
The next change occurred in 1963 or 1964 (depending on model) when the angles of the gear teeth
were changed to quieten the baulk ring gearbox. The modified gears w ere known as B Type gears , the
1962-63 gears retrospectively becoming known as A Type gears . So there you have it: 1959-62 Cone
Synchromesh gearbox, 1962-63/64 A Type Gears gearbo x and 1963/64-68 B Type Gears gearbox (plus, in
1963-64, an A Type gearbox with B Type 1st/2nd synchroniser and reverse idler...!).
Gearbox Identification
Identifying your 3 synchro gearbox can be a ver y complicated process, bourne out by the unfor tunately
necessarily complex guidelines below.
Between the three 3 synchro gearbox types, many, many components are not interchangeable. This
makes it especially important to identify your gearbox before ordering par ts, which can be difficult,
particularly when trying to work out whether you have A or B Type gears . Originally, gearbox cases
were stamped with a part number denoting the gear types within and the model application; however
this has become quite irrelevant over the years as gearboxes have been rebuilt, very often with different
components to overcome the lack of original parts availability.
The only surefire way to identify the gearbox nowadays is to inspect the internals with a check list to
hand, paying particular attention to:
(i) the presence of synchro cones or baulk rings (denoting a Cone Synchro box in the first instance and
an A Type or B Type box in the second);
(ii) If baulk rings are present, establish whether the second and third gears run on bushes (the bush
interlocking ring being visible between the two gears on the mainshaft gear cluster) or bearings . A Type
gearboxes except in the 1963 Cooper 997 run on bushes; the second and third gears in A Type
gearboxes in the 1963 Cooper 997 run on bearings, as is the case with the similarly shor t-lived Cooper
and Cooper S gearbox with hybrid A/B Type gears and all gearboxes with B Type gears.
(iii) Count the number of teeth on the laygear cluster. A combination of 13/19/24/28 teeth is the
regular set-up for non Cooper models and 13/19/23/26 for Cooper. Other combinations were available
only as Special Tuning options.
(iv) Are the laygear bearing circlips on the outside or inside of the bearings Cone Synchro and A Type
gears except 1963 Cooper 997 use outside laygear bearing circlips, whereas A Type gearbox in the 1963
Cooper 997, the hybrid A/B Type gearbox and B Type gearboxes use inside circlips.
The laygear should tell you which combination of gears you have... we say ‘should’ because the laygear
part number was traditionally stamped on the component between the lar gest and second largest gears,
but some reproduction gears (mostly in the case of 22G1100) don’t have this stamping. Identifying
your laygear allows you to work out what other gears have been used in the gearbox, since they were
designed to go together as matched gear sets and are usually not interchangeable. For this reason, all
the other major components in this section use the application remarks shown alongside the laygears -
even if it’s a bit long-winded sometimes, it positively matches the sets together.
Be careful with gearboxes in 848 models and 997 Coopers using A Type gears , though - some have been
converted from cone synchro to baulk ring A Type gears, retaining the original laygear ; some other
components used in cone to baulk ring converted gearboxes are unique and most are not listed here
(this catalogue section is complicated enough!). The 22G1100 laygear,incidentally, was for a short
period at the start of its life known as and stamped as 22G232. Lastly, if you find 22G83 or 22G714
on your laygear, you have an Austin/Morris 1100 or 1300 gearbox, not a Mini one.
Parts Availability
Unfortunately, parts availability ranges from almost hopeless (Cone Synchromesh and A Type gears)
through to pretty awful (B Type gears) and this situation is unlikely to improve greatly in the future.
The B Type gears do, however, benefit marginally from the fact that the MG Midget continued to use
versions of them until 1974, which slightly increases parts demand and availability. Many parts listed in
this section are therefore shown only as a matter of reference.
We will always do our utmost to help you seek out parts for your gearbox, but by rule of thumb the
thing to remember here is don’t embark on a 3 synchro gearbox rebuild until (a) you’re absolutely sure
you have the parts you need; and (b) you’ve weighed up seriously the benefits of sourcing another,better
condition, gearbox instead. You have been war ned...
Close Ratio and Straight Cut Gears
Close ratio straight cut gear sets are available to build into gearboxes with B Type Gears components, as
a special order. Please contact Somerford Mini for details. Similarly, please contact us if you have
factory-optional (Special Tuning) helical close ratio, straight cut close ratio or straight cut
standard ratio gears in your gearbox and you require replacement parts.
Reverse Idler Gear
1 22A377 REVERSE IDLER, with bush, 18 teeth 1 1959-64; 848 models, Cone Synchro
and A Type gears.
1961-62; 997 Cooper, Cone Synchro.
1962-63; 997 Cooper, A Type gears .
1963; 997 Cooper, A Type gears .
22G202 REVERSE IDLER, with bush, 18 teeth 1 1963-64; 997/998 Cooper, 1071
Cooper S , A Type gears with B Type
1st/2nd synchroniser and reverse.
1964-68; 848 and 998 (not Cooper)
models, B Type gears .
1964-68; 998 Cooper, 970/1071/1275
Cooper S, B Type gears .
2 2A3475 BUSH, reverse idler 1
3 DAM8038 SHAFT, reverse idler 1
Laygear
4 22A381 LAYGEAR, 13/19/24/28 teeth 1 1959-64; 848 models, Cone Synchro
and A Type gears.
22A350 LAYGEAR, 13/19/23/26 teeth 1 1961-62; 997 Cooper, Cone Synchro.
22G76 LAYGEAR, 13/19/23/26 teeth 1 1962-63; 997 Cooper, A Type gears .
22G197 LAYGEAR, 13/19/23/26 teeth 1 1963; 997 Cooper, A Type gears .
22G204 LAYGEAR, 13/19/23/26 teeth 1 1963-64; 997/998 Cooper, 1071
Cooper S , A Type gears with B Type
1st/2nd synchroniser and reverse.
22G231 LAYGEAR, 13/19/24/28 teeth 1 1964-68; 848 and 998 (not Cooper)
models, B Type gears .
22G1100 LAYGEAR, 13/19/23/26 teeth 1 1964-68; 998 Cooper, 970/1071/1275
Cooper S, B Type gears .
5 22A1371 LAYSHAFT 1
6 2A3581 PLATE,locating reverse idler shaft/layshaft 1
7 88G396 BEARING, needle roller, laygear 2
8 22G277 DISTANCE PIECE, bearing 1
9 22G278 CIRCLIP, bearing retaining 2
10 88G325 WASHER, thrust, large 1 0.123-0.124" (3.12-3.14mm).
88G326 WASHER, thrust, large 1 0.125-0.126" (3.17-3.20mm).
88G327 WASHER, thrust, large 1 0.127-0.128" (3.22-3.25mm).
88G328 WASHER, thrust, large 1 0.130-0.131" (3.30-3.32mm).
11 88G324 WASHER, thrust, small 1
1st Motion Shaft
12 22A88 SHAFT, 1st motion, 19 teeth, with cone 1 1959-62; 848 models, Cone Synchro.
22A588 SHAFT, 1st motion, 19 teeth 1 1962-64; 848 models, A Type gears.
22A257 SHAFT, 1st motion, 20 teeth, with cone 1 1961-62; 997 Cooper, Cone Synchro.
22A416 SHAFT, 1st motion, 20 teeth 1 1962-63; 997 Cooper, A Type gears .
22A592 SHAFT, 1st motion, 20 teeth 1 1963; 997 Cooper, A Type gears .
1963-64; 997/998 Cooper, 1071
Cooper S , A Type gears with B Type
1st/2nd synchroniser and reverse.
22A979 SHAFT, 1st motion, 19 teeth 1 1964-68; 848 and 998 (not Cooper)
models, B Type gears .
22A982 SHAFT, 1st motion, 20 teeth 1 1964-68; 998 Cooper, 970/1071/1275
Cooper S, B Type gears .
13 2A3693 CONE, synchronising 1 For 22A88 and 22A257 1st motion shafts.
Note that synchro cones have to be shrunk onto their respective gears and then finally machined - not a
task for most home-based Mini restorers.
14 22G2033 RING, baulk 1 For all other 1st motion shafts .
15 22G314 BEARING, 1st to 3rd motion shaft 1 For 22A88, 22A588, 22A257 and
22A416 1st motion shafts .
CHM172 BEARING, needle roller, 1st to 3rd 1 For 22A592, 22A979 and 22A982
motion shaft
1st motion shafts.
16 2A3709 BEARING, 1st motion shaft 1 In gearbox case.
17 2A3710 CIRCLIP, bearing retaining 1 0.094-0.096" (2.39-2.44mm)
2A3711 CIRCLIP, bearing retaining 1 0.097-0.099" (2.46-2.51mm)
Tel. 01249 721421 Fax. 01249 721316 www.somerford-mini.co.uk
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