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