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Gearbox Q&A


Removing the Gearbox

I have followed the workshop manual and stripped out the seats and
floor. We are now following ‘removal and replacement of gearbox and have
just removed the split pin nut, washer and rubber bush under the engine
mounting. We are unable to remove the clevis pin from the forked bolt.
I have looked at the Engine mounting illustration M27 but can see no way
to push or grip the clevis pin. It seems to be right up inside the
housing with very little space around it. We could undo the rear engine
mounting bracket and I think remove the rubber mountings and then see if
the position of the clevis pin is clearer.


There is no need to remove the clevis pin, it stays attached to the gearbox as in the photo. Once the nut, washer and rubber cup are removed, just lift the gearbox up; the rear rubber mounts are actually ‘loose’.



Gearbox YB TD

My original YB gearbox having been scrapped when the firm, in whose
hands it was, suddenly shut shop, I bought one which had come from a TD.
Can I assume it will be suitable for my YB?



The TD ‘box is identical right down to its ratios, BUT the TD has a rear extension for its gear lever. The Y’s lever fits where this extension bolts on, a simple job. YB ‘box in the photo.











Gear ratios 

Dear Neil,
I would like your advice regarding the gearing of my YB. I always thought that it was under-geared and the old engine would reach high revs without a lot of speed. Knowing that the engine had a lot of wear I decided that a re-build was necessary, so last winter I had the engine out and had a re-bore and crank grind. While the engine was out I also bit the bullet and put in a Ford Type 9 gearbox. All has gone together well and the car has been back on the road for some months but I still feel that the gearing is wrong. I have fitted a temporary rev counter in order to get a better understanding of what is going on and in 4th gear I get 40 MPH at 3000 revs (This is the same for both the old YB gearbox and the Ford 9 gearbox). The manual says that at 40MPH I should only be revving at 2756. So the only thing I can now think of is the real axle/ Diff might not be right. I have jacked up one of the rear wheels and counted the prop. shaft revolutions to the wheel and I get a ratio of 2.5-1. I am not sure this is the right way of measuring the diff. ratio as doing it with one wheel of the
ground causes the planetary gears to come into play. Can you offer me any advice as to the proper way to check the ratio and or what marks or numbers I should be looking for on the axle case? I have attached a photo (not easy to get a good one when still on the car) just in case that helps you identify the axle.



From my book “The Morris Ten Gearbox”. I think you have a Morris Ten Series ‘3’ diff! All these cars use the same axle casing but of differing widths.

“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.”


I have now checked my axle and am sure that it is from a YA as the
ratio is 5.143:1. Having now done some maths on the difference between the YA
and YB axles it appears to me that the 5.125:1 axle will only improve
performance by 0.35%. Is it worth changing the axle for this small improvement? By
the way I have checked that I have 15 inch wheels.
Any thoughts that you have would be welcome.


Fitting a YB axle is not worth the bother for such a tiny difference. If
you have radial-ply tyres fitted you will have reduced the wheel
diameter quite substantially!



Gearbox mounting

I own a 1949 YA and would like to replace the gearbox mounts. Having
received the replacements from the club and read the workshop manual I have two questions to ask.
Does the floor boards have to come out?
Where exactly would you jack up the rear of the engine to release the
old mounts? Any other advice or information would be greatly received.



You need to remove the gearbox cover which means at least one seat as well, though both will make access easier. A block of wood under the gearbox bell-housing and a screw-jack will support the gearbox, it does not need to be lifted very much. Undo the little eye-bolt anchor UNDERNEATH the gearbox rear end, this has two rubber cup-washers with a stiff-nut. You can then jack up the g/box enough to lift out the two rear mounts, they are LOOSE held in by the weight. NOTE how they fit BEFORE removing. Fit the new rubber, drop the g/box onto them, refit the eye-bolt washers and stiff-nut. Job done. The eye-bolt holds the gearbox down on its mounts.



Gear box oil selection
A chum is changing the oil in the YA gear box and back axle tomorrow. I am ashamed to say that the oil has not been changed in the 15 years that we have owned the car !. Unable to quickly locate Neil Cairns email address so hence the note to you. The question is simply is Carlube EP85w140 HD Gear Oil suitable for the job ? The handbook says Castrol Hi Press 140 which I have been unable to find..


Any modern EP140 will be OK. Oils today are far superior to those of the early 1950s. EP140 can be found in Halfords or most Agricultural Sales (tractors etc).