Manual Gearbox - 3 Synchro Internal Components

Final Drive (Differential)
No. Part No. Description Qty. Remarks No. Part No. Description Qty. Remarks
Final Drive Assembly
You will need to establish several things before embarking on a rebuild of your final drive:
The first thing (and the easiest) is to work out which drive shafts your Mini has. Rubber coupling (or
‘Moulton’) drive shafts were used on most Minis up until 1973. The exceptions were the Cooper S and
automatic transmission models, which used universal joint (or ‘Hardy Spicer’) drive shafts up until that
date. From 1973 onwards, all Minis used offset sphere (or ‘pot joint’) drive shafts. The designs of the
final drive output shafts and their covers depend on the drive shafts fitted. While rebuilding a final
drive on a rubber coupling Mini, you can easily convert it to take ‘pot joint’ drive shafts if you wish by
fitting a pair of DAM3114 output shafts and 22G2688 circlips .
The final drive gear also needs to be identified. This may be achieved by counting the number of teeth
on the final drive gear and if you divide that number by the number of teeth on the corresponding
final drive pinion in the gearbox, you’ll get the final drive ratio. If you are unsure whether the age of
your Mini’s transmission matches the age of the car,you will also need to work out whether you have
pre-A Plus or A Plus gears. A Plus gears were introduced on the Mini round about 1982 (at different
times on different models...), and have a sharper tooth angle and different pitch making them quieter
than, but definitely not interchangeable with, the earlier gears. Looking in the gearbox, A Plus gears can
be identified by the presence of a circumferential groove in the centre of the teeth, and the final drive
pinion on the gearbox mainshaft is machined flush on both sides .
The only exception to this rule concerns cars with the 3.444:1 final drive ratio, which received A Plus
final drive gears in 1979, a full 3 years before they got A Plus gearboxes. So, if you have a 3.444:1
final drive Mini with a pre-A Plus gearbox containing the larger idler gear and 1st/3rd motion shaft
bearings introduced in 1979, the chances are you will have A Plus final drive gears.
Lastly, you will need to identify your differential case. The case was redesigned in the early 1980s to
combat the problem of spinning pinion thrust washers wearing through it: notches were added to the
case to locate anti-rotation tabs on redesigned thrust washers.
For those indulging in modified or competition Minis, several flavours of limited slip differential and a
stronger cross pin differential are available as special orders; please contact Somerford Mini to
discuss your needs.
1 BTA145 CASE, differential 1 Use with plain pinion thrust washers.
DAM6027 CASE, differential 1 Use with anti-rotation thrust washers.
2 ATA7378 BUSH, differential case 1 Included in differential case.
Final Drive Gears, Manual Gearbox
3 22G443 GEAR, final drive, 65 teeth, 4.333:1 ratio 1 For 15 tooth 22G99 pinion.
22G370 GEAR, final drive, 64 teeth, 4.267:1 ratio 1 For 15 tooth 22G99 pinion.
22G101 GEAR, final drive, 62 teeth, 4.133:1 ratio 1 For 15 tooth 22G99 pinion.
22G340 GEAR, final drive, 63 teeth, 3.938:1 ratio 1 For 16 tooth 22G338 pinion.
22A401 GEAR, final drive, 64 teeth, 3.765:1 ratio 1 For 17 tooth 22A399 pinion.
22G940 GEAR, final drive, 62 teeth, 3.647:1 ratio 1 For 17 tooth 22A399 pinion.
22A411 GEAR, final drive, 62 teeth, 3.444:1 ratio 1 For 18 tooth 22A413 pinion.
DAM3645 GEAR, final drive, 65 teeth, 4.333:1 ratio 1 For 15 tooth DAM3647 pinion; A Plus.
DAM3216 GEAR, final drive, 63 teeth, 3.938:1 ratio 1 For 16 tooth DAM3218 pinion; A Plus.
DAM4779 GEAR, final drive, 64 teeth, 3.765:1 ratio 1 For 17 tooth DAM4131 pinion; A Plus.
DAM4162 GEAR, final drive, 62 teeth, 3.647:1 ratio 1 For 17 tooth DAM4131 pinion; A Plus.
DAM2677 GEAR, final drive, 62 teeth, 3.444:1 ratio 1 For 18 tooth DAM2679 pinion; A Plus.
DAM2806 GEAR, final drive, 61 teeth, 3.211:1 ratio 1 For 19 tooth DAM2808 pinion; A Plus.
DAM6327 GEAR, final drive, 59 teeth, 3.105:1 ratio 1 For 19 tooth DAM2808 pinion; A Plus.
DAM5925 GEAR, final drive, 59 teeth, 2.950:1 ratio 1 For 20 tooth DAM5927 pinion; A Plus.
TCB10004 GEAR, final drive, 58 teeth, 2.762:1 ratio 1 For 21 tooth TCC10001 pinion; A Plus.
Final Drive Gears, Automatic Transmission
22A1003 GEAR, final drive, 72 teeth, 3.273:1 ratio 1 For 22 tooth 22A1300 pinion.
DAM7362 GEAR, final drive, 72 teeth, 3.273:1 ratio 1 For 22 tooth DAM7365 pinion; A Plus.
DAM4130 GEAR, final drive, 69 teeth, 2.760:1 ratio 1 For 25 tooth DAM4128 pinion; A Plus.
4 ATA7378 BUSH, final drive gear 1 Included in final drive gear.
5 ATA7043 BOLT, gear to differential case 6
6 ATA7385 LOCK TAB, bolt 3
7 BTA154 BLOCK, thrust 1 Optional in D AM6027 differential case.
8 DAM6624 PINION, differential 2
9 2A7062 WASHER, pinion thrust, plain 2 Use in BTA145 differential case.
10 DAM5071 WASHER, pinion thrust, with anti-rotation 2 Use in DAM6027 differential case.
tab
11 22G2583 CROSS PIN, pinion 1
12 RPS1418 ROLL PIN, cross pin 1
13 22A373 OUTPUT SHAFT AND GEAR 2 For rubber (‘Moulton’) couplings .
22A1151 OUTPUT SHAFT AND GEAR 2 For universal joints (‘Hardy Spicer’).
DAM3114 OUTPUT SHAFT AND GEAR 2 For offset spheres (‘pot joints’).
14 BTA101 WASHER, output gear thrust 2
15 AHU1856 BEARING, differential 2
16 2A3535 SHIM, bearing, 0.002" (0.0508mm) A/R
2A3534 SHIM, bearing, 0.003" (0.0762mm) A/R
DAM3108 SHIM, bearing, 0.006" (0.1520mm) A/R
DAM3109 SHIM, bearing, 0.010" (0.2540mm) A/R
DAM3633 SHIM, bearing, 0.020" (0.5080mm) A/R
17 88G477 DISTANCE PIECE, with bush 1 Automatic transmission models; for
universal joint (‘Hardy Spicer’) shafts.
CHM166 DISTANCE PIECE, with bush 1 Automatic transmission models; for
offset sphere (‘pot joint’) drive shafts.
18 22G421 BUSH, distance piece 1 Automatic transmission models; for
universal joint (‘Hardy Spicer’) shafts.
2A3538 BUSH, distance piece 1 Automatic transmission models; for
offset sphere (‘pot joint’) drive shafts.
Final Drive Output
Rubber Coupling (‘Moulton’) Type
All Manual Gearbox Models Except Cooper S, 1959-73
19 CHM85 COVER ASSEMBLY, with bush 2
20 2A3538 BUSH, cover 2
21 ADU5738 OIL SEAL, cover 2
22 GUG705567GM GASKET, cover 2
23 SH505101 SCREW, coarse thread, cover to gearbox 10
24 LWZ305 WASHER, locking 10
25 22A374 FLANGE, output 2
26 FNZ810 NUT, output flange to shaft 2
27 PWZ110 WASHER, plain 2
28 GCD101 RUBBER COUPLING KIT, drive shaft 2 Includes one coupling, U bolts and nuts.
QL5000 NYLON COUPLING KIT, drive shafts 1 Uprated; includes two nylon and needle
roller couplings, plus U bolts and nuts.
29 22A132 U BOLT, coupling to shaft yokes 8
30 LNZ205 NUT, locking 16
Universal Joint (‘Har dy Spicer’) Type
Cooper S, 1963-71; All Automatic Transmission Models, 1965-73
31 22G419 COVER ASSEMBLY, with bush 2 Cooper S.
32 22G421 BUSH, cover 2 Cooper S.
33 AHU1082 OIL SEAL, cover 2 Cooper S.
34 GUG705567GM GASKET, cover 2 Cooper S.
35 SH505101 SCREW, coarse thread, cover to gearbox 10 Cooper S.
36 LWZ305 WASHER, locking 10 Cooper S.
37 88G476 COVER ASSEMBLY, with bush 2 Automatic transmission models .
38 22G421 BUSH, cover 2 Automatic transmission models .
39 AHU1082 OIL SEAL, cover 2 Automatic transmission models .
40 22A1612B GASKET, cover 2 Automatic transmission models .
41 SH505081 SCREW, coarse thread, cover to gearbox 8 Automatic transmission models .
42 LWZ305 WASHER, locking 8 Automatic transmission models .
43 22A1152 FLANGE, output, with bolts 2
44 22A1139 BOLT, output flange to drive shaft 8
45 LNZ405 NUT, locking, output flange bolt 8
46 22A1104 SCREW, output flange to output shaft 2
47 WE600101 WASHER, shakeproof 2
48 22A1201 WASHER, plain 2
49 88G493 COLLET, output flange 4
50 22A1566 RING, sealing 2
Offset Sphere (‘Pot Joint’) Type
All Models, 1973 On
51 CHM85 COVER ASSEMBLY, with bush 2 Manual gearbox models.
52 2A3538 BUSH, cover 2 Manual gearbox models.
53 ADU5738 OIL SEAL, cover 2 Manual gearbox models.
54 GUG705567GM GASKET, cover 2 Manual gearbox models.
55 SH505101 SCREW, coarse thread, cover to gearbox 10 Manual gearbox models.
56 LWZ305 WASHER, locking 10 Manual gearbox models.
57 CHM167 COVER ASSEMBLY, with bush 2 Automatic transmission models .
58 2A3538 BUSH, cover 2 Automatic transmission models .
59 ADU5738 OIL SEAL, cover 2 Automatic transmission models .
60 22A1612B GASKET, cover 2 Automatic transmission models .
61 SH505081 SCREW, coarse thread, cover to gearbox 8 Automatic transmission models .
62 LWZ305 WASHER, locking 8 Automatic transmission models .
63 22G2688 CIRCLIP, output shaft 2
64 GCV1102 OFFSET SPHERE C.V. JOINT ASS’Y 2 ‘Pot’ joint.
65 GSV1073 GAITER KIT, offset sphere joint 2 Includes one gaiter, clips and grease.
66 AKF1457 GREASE, sachet, offset sphere joint A/R
Tel. 01249 721421 Fax. 01249 721316 www.somerford-mini.co.uk
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