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?

[Steve Kerswell]

She is Polish, works in an old peoples home, just right for Dutton owners :-)) her name is Erin Mental, which worries me !!

[Liam Bourne]

I've got a 2.88lsd jaguar powrlok out of an XJ12 in mind. 0-60 in no idea but the V8 pulls 3rd from walking pace to 90mph. I've hit 116 in fifth at about 4 -4.5 and the engine revs to 7k. 1st and 2nd gear are hilarious and 1st just sits the rear near the floor before the wheels spin. I had a 3.54 in it before and it was too low for the power and torque of the engine. When driving on back roads you can just use 3rd and 4th gear and it bombs along nicely.

[Big Vern]

The 3.54 will work with an xflo if you're not interested in acceleration/performance, it wont improve fuel economy since its the Duttons awful aerodynamics that affect FC most. Remember the 3.54 was only available in pinto engined escorts for a good reason. If its only pulling around 3500 rev.min in fourth at 70mph then you'll likely be in third a lot at speeds below 60mph Though it pains me to say it if you want cruising speeds with low engine speed then fit a Rover V8, at lease it'll sound cool.