Someone teach me diff ratios

[learyd]

for a up to 100bhp moggy what would be a good axle and diff ratio? and can you explain what the diff ratio numbers mean?

[Alec]

Hello Learyd,

the ratio is the gearing, i.e. how many turns of the input from the engine to the number of turns out to the wheels.

I don't know what would be good for a 100 bhp Morris, and also is dependant on the size of tyres you fit. The other aspect is do you want high speed cruising or acceleration. Low ratios (High gearing) give more relaxed cruising but less acceleration and vice versa.

Alec

[PSL184]

I guess many would choose the ford axle with a 3.54 diff for this kind of set up....

[bmcecosse]

But if using the Minor axle - the best you can get is the 3.7 final drive from Wolselely 1500/Riley 1.5 - or later Spridgets. Trouble will be with the half shafts - which are the weakest link. There are 'hardened' ones available - at a price.

How are you going to achieve this 100 bhp ??

[learyd]

i think i would probably prefer accleration to cruising, as to the 100bhp not really sure yet but probably gonna make it a hotted up a series

[learyd]

something else to add supposedly the mk1 capri axle can fit onto the minor without any shortening in width, has any one heard of this conversion or done it?

[bmcecosse]

By no means impossible to get the 100 bhp - but it won't be inexpensive!

[charlie_morris_minor]

something else to add supposedly the mk1 capri axle can fit onto the minor without any shortening in width, has any one heard of this conversion or done it?

yes mk1 capri do fit and have the advantage of the locating brackets being the same size and in the same position as on the moggy.

later mk 3 axle will fit having the same mounting points but are a little to wide to fit under an unmodified wing

[charlie_morris_minor]

But if using the Minor axle - the best you can get is the 3.7 final drive from Wolselely 1500/Riley 1.5 - or later Spridgets. Trouble will be with the half shafts - which are the weakest link. There are 'hardened' ones available - at a price.

something i have always wondered about..

the point of failure in the standard moggy axle is the halfshaft..
you replace the half shafts with hardened ones great..

but are you not "pushing" the point of failure into the diff? or can the diff happily handle 100bhp?

[plastic_orange]

Diffs are not the strongest either - I'd go for the Ford option if increasing the power. Even a standard 1098 can break diffs.

Pete

[bmcecosse]

A limited slip diff spreads the load around much better......... But really - it's starting away with wheel spin and axle tramp that tend to break shafts and diffs - not normal motoring, no matter how strong the engine.

[learyd]

bad news, due to being 17 and insurance being far to high i have to stick with an original 948cc for another 2 years, meanwhile thinking of still building the car to take larger a series in the future, could the 948cc drive a escort or capri axle and sierra type 9 5 speed or is it asking to much of the wee engine?

[bmcecosse]

No - it can 'drive' them - but the top gear ratio is likely to be too high for the lowly 948. But then - you can just drive in 4th gear for the next two years !!!

[learyd]

But the escort axle would still be fine?

[charlie_morris_minor]

why would you want to do it on its own?

you will need to either change the stud pattern on one of your axles or run different wheels front and rear?

I would also be suprised if you can get away with using the original prop shaft.. so you would have to change the prop shaft now and change it again ( probably ) when you change the gear box.

If you are desperate to change the gear ratio on your moggy get a different moggy / wolsely dif.. you could probably sell it for the same as you paid for it when you do all your mods so it would not cost much ( a couple of hours work and a few new gaskets ).

[bmcecosse]

Oh no - prices of these rare and highly desirable 3.7 diffs are rising fast! Some are said to be hoarding them - to make a killing in the future!!

[53buick]

Just fitted a 3.7 diff to my wife's traveller, made one hell of a difference...
it was a 948cc then the previous owner changed the engine for an 1100 so she was revving to high all the time when cruising.
Stock Diff was 4.55:1, I fitted Weller 13" wheels on and this made things so much worse!
Now the 3.7 is in it is great.
I have just bought a 5 speed conversion to fit against the 1100 which I will be doing soon, this will make a lovely cruiser I think!
I will feed back any issues.
Spence & Paula