Manual Gearbox - 3 Synchro Internal Components

Manual Gearbox - Primary, Idler and 1st Motion Shaft Drive Gears
No. Part No. Description Qty. Remarks No. Part No. Description Qty. Remarks
Primary, Idler and 1st Motion Shaft Drive Gears
Several different combinations of primary gear and bushes were used on the ear liest Mini power units
built between 1959 and 1963, following the abject failure of the first, the so-called ‘D.U.’ bush and oil
seal design (which allowed engine oil seepage onto the clutch all too frequently). As an interim
measure, a revised oil-fed bush system was fitted - in most cases when the car came in for the
inevitable clutch replacement - and after a couple of false starts the ‘Deva’ dry-lubricated bush became
the standard fitment. Each system necessitated a different engine crankshaft and flywheel, as well as
the primary gear and bushes. Extra care must be taken to select matching components for these ear ly
designs.
From 1963 onwards, crankshaft, flywheel, primary gear and bush combinations settled down into tw o
designs, depending on the crankshaft tail dimensions: one combination for 848, 998 and 1098 engines
and the other for 1071, 1275 and 970 engines. This continued right the way through to 1979 when ‘A
Plus’ gears were introduced, which saw production out through to 2000.
Primary gears are supplied with their bushes fitted, as ready-to-use assemblies, from Somerford
Mini. However, if you intend to fit replacement bushes in a primary gear, the bushes must be
machined after fitment to ensure alignment with each other.
By contrast, the idler and 1st motion shaft drive gears saw far fewer changes, being limited to 3
synchro gearbox (1959-68), pre-A Plus 4 synchro gearbox (1968-79) and A Plus (1979 on). Of these,
pre-A Plus 4 synchro gears may be used on 3 synchro gearboxes if certain other components are fitted
at the same time. However, pre-A Plus and A Plus gears cannot be mixed and matched together.
Bearings (and their retaining circlips) for the idler and drive gears may be found in the ‘Flywheel
Housing and Clutch Cover’ and ‘Manual Gearbox - External’ sections of this catalogue. Primary, idler and
drive gears for automatic Minis may be found in the ‘Automatic Transmission - Torque Converter and
Housing’ section.
Primary Gears
Confusion often reigns over the convention for naming primary gear bushes. Which should be called the
front bush and which should be the rear The answer is the bush closer to the front of the engine
(i.e. the water pump end) is the front bush and the bush on the clutch end (the ‘top hat’ bush on
post-1962 cars) is the rear bush. Hope that sorts it out.
1959-62, Oil-fed Bush 848 Engines
1 22A79 PRIMARY GEAR, with bushes, 24 teeth 1
2 22A81 BUSH, primary gear,front 1
3 22A82 BUSH, primary gear,rear 1
1961-62, Oil-fed Bush 997 Engines
4 12A380 PRIMARY GEAR, with bushes, 24 teeth 1
5 12A386 BUSH, primary gear,front 1
6 12A385 BUSH, primary gear,rear 1
1962-63, Deva Bush 848 Engines, 1 3/8" dia. Flywheel Machining
7 22A520 PRIMARY GEAR, with bushes, 24 teeth 1
8 22A447 BUSH, primary gear,front 1
9 22A448 BUSH, primary gear,rear 1
1962-63, Deva Bush 997 Engines, 1 3/8" dia. Flywheel Machining
10 22G106 PRIMARY GEAR, with bushes, 24 teeth 1
11 22G108 BUSH, primary gear,front 1
12 22G109 BUSH, primary gear,rear 1
1963, Deva Bush 997/998 Engines, 1 1/2" dia. Flywheel Machining
13 22A551 PRIMARY GEAR, with bushes, 24 teeth 1
14 22A553 BUSH, primary gear,front 1
15 22G109 BUSH, primary gear,rear 1
1963-92, Deva Bush 848/998/1098 Engines, 1 1/2" dia. Flywheel Machining
16 22A1493 PRIMARY GEAR, with bushes, 24 teeth 1 1963-79.
DAM8888 PRIMARY GEAR, with bushes, 29 teeth 1 1979-92; A Plus.
17 DAM2821 DUST SHIELD 1 1979-92; A Plus.
18 DAM8887 BUSH, primary gear,front 1
19 22G109 BUSH, primary gear,rear 1
1963 On, Deva Bush 970/1071/1275 Engines, 1 1/2" dia. Flywheel Machining
20 22G1053 PRIMARY GEAR, with bushes, 24 teeth 1 1963-79.
DAM8890 PRIMARY GEAR, with bushes, 29 teeth 1 1979 on; A Plus. Not France 1990-96.
DAM9373 PRIMARY GEAR, with bushes, 30 teeth 1 A Plus. France 1990-96.
21 DAM2821 DUST SHIELD 1 1979 on; A Plus.
22 DAM8889 BUSH, primary gear,front 1
23 22G109 BUSH, primary gear, rear 1
Primary Gear Front Thrust Washers
848, 997, 998 and 1098 Engines, Except 848 Engines 1962-63
24 22A321 WASHER, thrust, primary gear, front 1 0.110-0.112" (2.79-2.84mm).
22A322 WASHER, thrust, primary gear, front 1 0.112-0.114" (2.84-2.89mm).
22A323 WASHER, thrust, primary gear, front 1 0.114-0.116" (2.89-2.94mm).
22A324 WASHER, thrust, primary gear, front 1 0.116-0.118" (2.94-2.99mm).
22A450 WASHER, thrust, primary gear, front 1 0.118-0.120" (2.99-3.04mm).
848 Engines 1962-63
25 22A295 WASHER, thrust, primary gear, front 1 0.123-0.125" (3.12-3.17mm).
22A83 WASHER, thrust, primary gear, front 1 0.125-0.127" (3.17-3.22mm).
22A238 WASHER, thrust, primary gear, front 1 0.127-0.129" (3.22-3.28mm).
22A239 WASHER, thrust, primary gear, front 1 0.129-0.131" (3.28-3.32mm).
970, 1071 and 1275 Engines
26 DAM6490 WASHER, thrust, primary gear, front 1 0.112-0.114" (2.84-2.89mm).
DAM6486 WASHER, thrust, primary gear, front 1 0.114-0.116" (2.89-2.94mm).
DAM6487 WASHER, thrust, primary gear, front 1 0.116-0.118" (2.94-2.99mm).
DAM6488 WASHER, thrust, primary gear, front 1 0.118-0.120" (2.99-3.04mm).
DAM6489 WASHER, thrust, primary gear, front 1 0.120-0.122" (3.04-3.09mm).
Primary Gear Rear Thrust Washers
1959-62, Oil-fed Bush 848 Engines
27 2A3597 WASHER, thrust, primary gear, rear 1
1961-62, Oil-fed Bush 997 Engines
28 12A382 WASHER, thrust, primary gear, rear 1
29 12A383 RING, backing 1
1962-63, Deva Bush 848 Engines With 1 3/8" dia. Flywheel Machining
30 2A3597 WASHER, thrust, primary gear, rear 1
31 22A449 RING, backing 1
1962 On,Deva Bush 970, 997, 998, 1098, 1070 and 1275 Engines
With 1 3/8" or 1 1/2" dia. Flywheel Machining
1963 On,Deva Bush 848 Engines With 1 1/2” dia. Flywheel Machining
32 22A319 WASHER, thrust, primary gear, rear 1
33 88G549 RING, backing 1
Idler Gears
34 22A304 IDLER GEAR, 31 teeth, 3/4" shaft dia. 1 1959-68; 3 synchro.
22G943 IDLER GEAR, 31 teeth, 3/4" shaft dia. 1 1968-79; 4 synchro.
TUB101310 IDLER GEAR, 37 teeth, 7/8" shaft dia. 1 1979 on; 4 synchro, A Plus.
The 3 synchro 22A304 idler gear may be replaced by the equivalent gear from the 4 synchro gearbox,
22G943, so long as the original circlip retaining the idler gear bearing in the gearbox case is replaced
with a 22G1141 circlip.
35 22A1545 WASHER, thrust, 0.130-0.131" (3.30-3.32mm) 2 1959-79; 3 synchro and 4 synchro.
22A1546 WASHER, thrust, 0.132-0.133" (3.35-3.37mm) 2 1959-79; 3 synchro and 4 synchro.
22A1547 WASHER, thrust, 0.134-0.135" (3.40-3.42mm) 2 1959-79; 3 synchro and 4 synchro.
22A1548 WASHER, thrust, 0.136-0.137" (3.45-3.47mm) 2 1959-79; 3 synchro and 4 synchro.
22A1549 WASHER, thrust, 0.138-0.139" (3.50-3.53mm) 2 1959-79; 3 synchro and 4 synchro.
DAM5914 WASHER, thrust, 0.130-0.131" (3.30-3.32mm) 2 1979 on; 4 synchro, A Plus.
DAM4822 WASHER, thrust, 0.132-0.133" (3.35-3.37mm) 2 1979 on; 4 synchro, A Plus.
DAM4823 WASHER, thrust, 0.134-0.135" (3.40-3.42mm) 2 1979 on; 4 synchro, A Plus.
DAM4824 WASHER, thrust, 0.136-0.137" (3.45-3.47mm) 2 1979 on; 4 synchro, A Plus.
DAM4825 WASHER, thrust, 0.138-0.139" (3.50-3.53mm) 2 1979 on; 4 synchro, A Plus.
1st Motion Shaft Drive Gears
36 2A3545 DRIVE GEAR, 1st motion shaft, 24 teeth 1 1959-68; 3 synchro.
22G849 DRIVE GEAR, 1st motion shaft, 24 teeth 1 1968-79; 4 synchro.
DAM2925 DRIVE GEAR, 1st motion shaft, 29 teeth 1 1979 on; A Plus. Not 1275 (France),
1990-96.
DAM6337 DRIVE GEAR, 1st motion shaft, 28 teeth 1 A Plus. 1275 (France), 1990-96.
The 3 synchro 2A3548 drive gear may be replaced by the 22G849 gear from the 4 synchro gearbox, so
long as distance piece C-STR239 is also used.
37 2A3548 NUT, drive gear to 1st motion shaft 1
38 DAM4000 LOCK TAB 1
Tel. 01249 721421 Fax. 01249 721316 www.somerford-mini.co.uk
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