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XPAG (+ other Nuffield) Gearbox & Axle Ratios

The Morris type gearbox that MG used up until the TF Midget was also fitted to other Nuffield cars between 1945 and 1956. Here is a detailed list of their gear and axle ratios.

 

Gearbox Specifications.

 

Remember, the ‘ratio’ given is the gearbox, but it is then multiplied by the rear axle ratio, so that is included as well. Two identical gearboxes fitted with different ratio rear axles, will appear different on paper as the overall ratio’s will not be the same. ( i.e. top gear ratio will be 1 to 1 in the gearbox as it drives straight through, but the overall ratio will be 1 multiplied by the rear axle ratio, 1 x 5.125 = 5.125. Second might be 2.25 x 5.125= 11.547.)

 

Morris Six Series ‘MS;-

 

First series,
First & reverse 3.214
Second 2.087
Third 1.344
Top 1.00 rear axle ratio 4.1

 

Second series,
First & reverse 3.214
Second 2.25
Third 1.446
Top 1.00 rear axle ratio 4.1 or 4.555

 

Wolseley 4/44 & Morris M.O. series;-

 

First & reverse 3.807
Second 2.253
Third 1.506
Top 1.00 rear axle ratio 5.125

 

Morris Ten Series 3

 

Reverse 5.149
First 4.00
Second 2.245
Third 1.529
Top 1.00 rear axle ratio 5.375

 

Morris Ten Series ‘M’

 

First & reverse 3.8
Second 2.241
Third 1.379
Top 1.00 rear axle ratio 5.286

 

M.G. TA Midget.

 

First & reverse 3.72
Second 2.20
Third 1.42
Top 1.00

after engine 684,
First & reverse 3.45
Second 2.04
Third 1.32
Top 1.00 rear axle ratio 4.875

 

M.G. TB & TC Midget.

 

First & reverse 3.38
Second 1.95
Third 1.36
Top 1.00 rear axle ratio 5.125

 

M.G. TD & TF Midget.

 

First & reverse 3.5
Second 2.07
Third 1.39
Top 1.00 rear axle ratio 5.125

 

M.G. YA, YT, & YB.

 

First & reverse 3.5
Second 2.07
Third 1.39
Top 1.00 YA, YT rear axle ratio 5.143
YB rear axle ratio 5.125
( YB has one inch smaller wheels.)

 

Oil suitable for the post was cars is SAE 90 EP, pre-war SAE 140.

The above includes the gear ratios and rear axle ratios of all the cars
that use the Nuffield Hypoid rear axle. You can fit a BMC rear differential and
pinion, but they will require machining to fit your axle casing. You
will also need to have your speedometer re-calibrated to any higher
ratio you use.

 

Neil Cairns.