English Diff Ratio's

[Adrian Southgate]

So I've got to a point where I need to make a decision on the diff but on checking them today I seem to have a bewildering range of ratio's. I assume that the numbers stamped into the crown wheel are part numbers and that a segment is the number of teeth on the pinion and another the crown wheel.

This being the case I have the following... 

That one is definitely 9-35 and I have a second one to match which needs new planet gears... Both have 69 part numbers so made in 1969?

That one is 11-39 and has a 71 part number and a large flange...

This is the one I have just taken out of the axle, looks much newer than the others but its a 10-39 and has a part number with no conspicuous date.

Now working from these numbers I would hazard a guess that the 10-39 is actually a 3.9:1 (3.89:1?)

That makes the 9-35 a 3.88:1 and the 11-39 a 3.54:1.

Bearing in mind i will be using a type 3 box and a 1630 xflow should I fit the 3.54:1?

[Paul Sheridan]

NO, NOooooo  NOOOooooooooo, you should be selling me the 3.54  :-))))))

[Adrian Southgate]

Oooooohhh..... Nah...

I suppose I should really dig deeper into box ratio's for the type 3 as well.

[Adrian Southgate]

I do still have these to play with too...

2 X Capri Salisbury axle casings which have been de-bracketed, one still has the diff bolted in and I don't know what type it is, I do have a 3.09:1 CWP set for this but its quite wide compared to the english ones. Third one down I haven't stripped yet but as it's a small flange I expect it to be a 3.89:1 or higher (or is it lower) There are two more complete english axles lurking under cars as well. Doubt if either of them will get used as project X and project Y will be 'different' drive trains.

I cleaned the axle casing a bit and the oil had very little metal in it (if any)

[John Allen]

I'd bite your arm off for the 3.09:1!!!!!!!!!???????

[Adrian Southgate]

All I have is the crown wheel and pinion though I don't know whats in the other Salisbury casing.

That differential is in stock at GS Escorts, Diff and planet gears £20, CWP set £80.

Do you have a salisbury axle fitted to one of yours then John?

ALSO... have you checked the ratio on the CWP set that was in the english you got from me? I seem to remember it having a tag on that said 4.44 or 4.41...

[John Allen]

Basically I'm trying to get a 3.09:1 set up for the s1

[Brian (up north) Morris]

what will that give you john ??

[Brian (up north) Morris]

so what will it do old man...?

[Brian (up north) Morris]

thanks dad. i still dont really understand diffs lol :-)

[Steve Kerswell]

so Ade, have you uncovered the dark art of diff building, spring balance and engineers blue? they have their own Masonic ring you know :-))

[Adrian Southgate]

Nope, i'm not stripping the actual diff's, way too much 'black arts' for me. I'm dead close to a company called Geartorque who are rather good with this sort of stuff so when the decision is made I will be taking the diff to them to have it checked over.

All three useable diffs have nice even wear marks on the teeth and little or no free play so I'm hoping to avoid another huge bill.

[James Doulton]

9-35 is 3.88888888888... so 3.89, the common ratio. I had never heard of 3.9 before this. I think 3.89 is your best ratio if you have a 5 speed box as 3.54 will make it unresponsive in 5th. If you have a 4 speed then maybe 3.54 wouldn't be too bad. I'll do some figures when I get back from volleyball.