MOWOG diff

[ba249k]

Hi All
I was hoping some of you knowledgeable chaps might shed some light on a 5.85:1 differential that I have fitted into my trials car.
I think the axle is from a Morris minor?
the diff is stamped 7524 MOWOG 7/41 which I think works out at 5.85 to 1?
This seems high to me even for a van or similar?
Could this be from any other type of vehicle?
I am just interested so any further info would be helpful.
Cheers

[philthehill]

I cannot remember ever coming across a 5.8 - 1 crown wheel and pinion though that does not mean that it was never made.
The diff charts that I have show the lowest diff ratio as 5.375 - 1.
The BMC/MOWOG diffs were used in all sorts of specialist vehicles and it could have come from any one of those.
The crown wheel & Pinion could have been fitted and come from the BMC Mini tractor which used the BMC 950 engine.
A photo of the diff, axle and markings would be appreciated.

[ba249k]

Hi
The casting number on the diff nose casting is VAF 5 AT8 7182.
I have tried to up load a couple of pics.
Hope it works!
Cheers
Barry

[ba249k]

As that worked here is a pic of the diff.


For information my Trial car was rescued from a scrap yard about 3 years and has now been totally rebuilt.
Originally from circ 1965 fitted with an A series engine and triumph front axle and a Morris rear axle?

[bmcecosse]

I think I prefer the original bodywork...... Are you allowed to weld up the diff for trials ??

[philthehill]

Many thanks for the pictures.
The axle casing is not post WW2 BMC Minor as the diff carrier/nose on your axle is secured by 10 studs and the Minor is secured by only 8 studs.
The diff carrier number does not match any of the known Minor carrier numbers.
I have not yet found a MOWOG/Morris axle casing with 10 studs securing the diff nose to the axle casing.
I did think that it may be a Triumph Dolomite axle but even that appears to be secured with 8 studs.
Have you counted the number of teeth on the crown wheel and the number of teeth on the pinion.
I will continue to look for a 10 stud casing.[frame][/frame]
I have a feeling that the axle casing is either an early MG or pre WW2 Morris Minor. The reasoning behind this is that the early MGs/Morris Minors had small engines and big wheels and would require quite a low ratio to give any performance.
Tomorrow If I can I will go and look at some old MGs and see if any have the same diff carrier.

[mike.perry]

Series MM and early Series II diffs were a completely different design and the diff unit was not removable from the axle so you can count that out.
Is 7/41 an Austin ratio?

[philthehill]

If the diff was welded you would not be able to have the use of the fiddle brakes/levers as fitted and shown in the picture of the car in the scrap yard.
Are fiddle brakes still allowed?

[bmcecosse]

Indeed! But there would be no need - a wonderful thing is a welded diff - the traction on my Autocross Mini was amazing!! Well spotted Phil on that casing having 10 studs - I had been thinking it all looked a bit 'big' for a Minor axle. Perhaps it's a commercial axle ? The PCD of the half shafts would perhaps be interesting.

[philthehill]

Just arrived back after checking the diff housings on my neighbours stable of MGs - they all have 8 studs for locating and mounting the diff carrier other than the TA which has 10 studs and a different diff carrier to the one shown above. So no progress there.
The two links below are for reference and possible exclusion of possible diff ratios.
http://mgaguru.com/mgtech/rearaxle/ra201.htm
http://www.mg-cars.org.uk/imgytr/hints% ... tdiffs.pdf

This is a link to a MOWOG 10 stud diff carrier gasket and which lists the vehicles it purports to fit http://www.ebay.co.uk/itm/DIFF-GASKET-r ... 1e94ad6895.
Someone may be able to take a lead off this.

The casing of the Austin Devon axle on the attached link looks to be the same especially around the spring mountings and it has the anti roll bar link mountings in the right place and if I have counted correctly it has 10 studs holding the diff carrier to the casing. Whether it is a 5.85 - 1 diff ratio I do not know.
http://www.ebay.co.uk/itm/AUSTIN-A40-DE ... 566c890ead

I have now discovered that the Austin A40 Devon Pick up (1948 - 1957, Austin type des GQU2 - U5) was fitted with a special low diff ratio (yet to be determined) and with 17" wheels had a max comfortable speed of 45/48mph so it must have been low! Fit 13" wheels and the overall gear ratio would have been very very low.

[ba249k]

Many thanks for all your efforts.
Great Respect!
I have counted the teeth and they are correct 7/41.
The Austin axle looks very similar?
Yes we use fiddler brakes, and no we can not weld up the diffs.
The body work is as a result of a combination of a rush to meet a deadline for a trial /a home garage and no body shop equipment. Once we have the mechanicals correct we will revisit the bonnet etc.
Currently fitting twin motorbike calipers to each rear disc and converting it to run on LPG via a Forklift truck carb.
All fun and games!
Thanks again for the info but don't go to too much trouble as it will not effect anything, it was just out of interest for the history of the car
Cheers
Barry

[philthehill]

Barry
No trouble at all; only too happy to help identify the axle/diff.
I have still got the dent in the lower rear panel of my Minor from sliding backwards and making contact with a tree when competing in a Production Car Trial many years ago before moving over to Speed Hill Climbing.
Sporting Trials used to be a regular feature on the television at one time but have not seen them on the box for some time.
When I worked in the BMC garage we used to look after a trials car for one of our customers but it had a Ford side valve fitted.
My neighbour with the MG stable undertakes Sporting Trials with one of his 1930s MG both here and on the continent but is forever pulling off the exhaust and other parts, he lost a stub axle last time out - so he has invested in a Austin 7 which apparently will go mostly anywhere.
If I come across any more info I will post on here.
Happy mud plugging
Phil

[bmcecosse]

All great stuff - but MOWOG = Morris Wolseley Garages so it never appeared on any Austin parts until after the BMC merger in 1952 - and then only when 'Morris' parts were used on Austins. That final drive may of course be a retro fit into an earlier Austin axle casing .

[philthehill]

The Austin A40 Devon pickup was still in production up to early 1957 (GQU5) so could/would fall within the MOWOG period.
The only diff carrier so far identified which may have such a low diff ratio and definably a similar axle case has been the A40 Devon pickup.
The other Austins - Devon (car), Dorset & Somerset all had higher crown wheel & pinion ratios during their production.
Also the above links show diff ratios higher than 5.85 - 1.
Whilst I have been unable to confirm the exact ratio of the A40 Devon pickup crown wheel and pinion my money is on the Austin A40 Devon pickup as being the donor/source vehicle.
I will endeavour to find out the exact crown wheel and pinion ratio of the A40 Devon pickup and post my findings on here.

[MarkyB]

Why are you converting it to run on LPG?
Doesn't it have less energy in it as well as needing a heavy tank?

[bmcecosse]

Wish my Trav was on LPG.... Half the price of petrol - yes slightly less energy but will run v high compr ratio due to 108 Octane Rating.

[MarkyB]

* LPG has a typical specific calorific value of 46.1 MJ/kg compared with 42.5 MJ/kg for fuel oil and 43.5 MJ/kg for premium grade petrol (gasoline).[6] However, its energy density per volume unit of 26 MJ/L is lower than either that of petrol or fuel oil, as its relative density is lower (about 0.5–0.58, compared to 0.71–0.77 for gasoline).

It must have been energy density I was thinking of


* Taken from wikipeadia of course.

[bmcecosse]

No - you were right enough - problem is we buy by volume - not by mass.

[MarkyB]

I guess that if you can use a tank that isn't too heavy, it wouldn't need to be as big as one for normal use then the benefit of the extra octane would make it worthwhile.

Would a fire extinguisher tank do the job?
Some quick research suggests maybe

[smithskids]

Barry, just found 2 Austin diffs with 5.85:1 ratio but they are from wartime 2 ton ambulance and 30cwt general service lorry so they may have carried on using this ratio after the war. They are listed as having 10.60X16" tyres.

cheers smithskids